Re: IDLE being too clever checking nonlocal declarations?
On Mon, 21 Oct 2013 23:26:28 -0400, Terry Reedy wrote: On 10/21/2013 7:52 PM, Steven D'Aprano wrote: On Mon, 21 Oct 2013 15:51:56 -0400, Terry Reedy wrote: On 10/21/2013 11:06 AM, Chris Angelico wrote: Try typing this into IDLE: def a(): def b(): nonlocal q SyntaxError: no binding for nonlocal 'q' found If you submit those three lines to Python from the command line, that is what you see. Arguably, that's also too strict, As I quoted from the doc, it is an error for a program to contain a nonlocal with no referent. The reason is one only needs nonlocal to bind and unlike with 'global newname', it would be undefined where to do the binding. Yep, I got that, but what I'm saying is that it is too strict to raise the exception at the point where it sees nonlocal q. The CPython interpreter allows q to be defined inside function a but after function b, e.g. this is allowed: def a(): def b(): nonlocal q q += 1 q = 2 # === If IDLE and the code.py module requires q to be strictly defined before function b, then it is too strict. Your analysis of the bug as being in code.py seems plausible. [steve@ando ~]$ python3.3 -c def a(): def b(): nonlocal q q = 1 What system lets you do that? (See other thread about Windows not allowing that, because newline terminates the command even after .) Is '' a line continuation marker (like '...' in Python)? Yes, sorry I should have said. That's bash, under Linux. Here's another way: steve@runes:~$ python3.3 -c def a():^M def b():^Mnonlocal q^M q=1^Mprint(a() is None) True Still bash under Linux (a different machine), the ^M is *not* a pair of characters ^ followed by M but an actually newline, generated by typing Ctrl-V Enter (that's the ENTER key, not the letters E n t e r). In theory I should be able to get something working with \n escapes instead of ^M, but I can't get it working. But I'm not an expect at bash's arcane rules for quoting and escaping special characters. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Python was designed (was Re: Multi-threading in Python vs Java)
On Tue, Oct 22, 2013 at 2:19 PM, rusi rustompm...@gmail.com wrote: On Tuesday, October 22, 2013 8:25:58 AM UTC+5:30, Peter Cacioppi wrote: Guess-who said: but it's ugly, by which I mean it is hard to use, error prone, and not easily maintained. OK, I see the problem. What you call ugly is really just objectively bad. You continue to not attribute quotes. What user agent/group are you using? I don't know what headers come through on comp.lang.python, but on the mailing list, I can see some clear fingerprints that it's the one so many of us hate... Message-ID: 6f511c0b-c5fa-4307-9a2a-cb73a1768...@googlegroups.com Complaints-To: groups-ab...@google.com Though I don't think the abuse address would do much with complaints regarding citation courtesy :) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: IDLE being too clever checking nonlocal declarations?
On Tue, Oct 22, 2013 at 4:57 PM, Steven D'Aprano st...@pearwood.info wrote: Yep, I got that, but what I'm saying is that it is too strict to raise the exception at the point where it sees nonlocal q. The CPython interpreter allows q to be defined inside function a but after function b, e.g. this is allowed: def a(): def b(): nonlocal q q += 1 q = 2 # === If IDLE and the code.py module requires q to be strictly defined before function b, then it is too strict. Your analysis of the bug as being in code.py seems plausible. Yeah. I came across this as I was knocking together a test for something else, and my work-around was to define the inner function as just pass, and then go back and edit in the nonlocal declaration after adding the assignment outside. The only problem is that it's syntax-checking something that's only half-entered, and is bombing on it - thus stopping you from typing in the bit that would make it valid. Thanks Terry for the extra info on the tracker issue. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Animated PNG Vs Gif: 120fr 3D Python Powered Logo
On 10/22/2013 1:28 AM, Metallicow wrote: Here is links to the apng/gif on ImageShack uploaded with the Do Not Resize option. Checked/Views fine with default Firefox/Opera browsers. Animated 3D Python Powered Logo apng - 120frames 1/60 sec http://img34.imageshack.us/img34/4717/f4l4.png Neat: I would actually have the rotation slower, but still smoothed. gif - 120frames about 1/10sec or as fast as it can go... http://img35.imageshack.us/img35/4231/j29.gif I can see the jerking. -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
Newline in bash, was Re: IDLE being too clever checking nonlocal declarations?
Steven D'Aprano wrote: On Mon, 21 Oct 2013 23:26:28 -0400, Terry Reedy wrote: On 10/21/2013 7:52 PM, Steven D'Aprano wrote: On Mon, 21 Oct 2013 15:51:56 -0400, Terry Reedy wrote: On 10/21/2013 11:06 AM, Chris Angelico wrote: Try typing this into IDLE: def a(): def b(): nonlocal q SyntaxError: no binding for nonlocal 'q' found If you submit those three lines to Python from the command line, that is what you see. Arguably, that's also too strict, As I quoted from the doc, it is an error for a program to contain a nonlocal with no referent. The reason is one only needs nonlocal to bind and unlike with 'global newname', it would be undefined where to do the binding. Yep, I got that, but what I'm saying is that it is too strict to raise the exception at the point where it sees nonlocal q. The CPython interpreter allows q to be defined inside function a but after function b, e.g. this is allowed: def a(): def b(): nonlocal q q += 1 q = 2 # === If IDLE and the code.py module requires q to be strictly defined before function b, then it is too strict. Your analysis of the bug as being in code.py seems plausible. [steve@ando ~]$ python3.3 -c def a(): def b(): nonlocal q q = 1 What system lets you do that? (See other thread about Windows not allowing that, because newline terminates the command even after .) Is '' a line continuation marker (like '...' in Python)? Yes, sorry I should have said. That's bash, under Linux. Here's another way: steve@runes:~$ python3.3 -c def a():^M def b():^Mnonlocal q^M q=1^Mprint(a() is None) True Still bash under Linux (a different machine), the ^M is *not* a pair of characters ^ followed by M but an actually newline, generated by typing Ctrl-V Enter (that's the ENTER key, not the letters E n t e r). In theory I should be able to get something working with \n escapes instead of ^M, but I can't get it working. But I'm not an expect at bash's arcane rules for quoting and escaping special characters. I usually just hit Return... $ python3.3 -c def a(): def b(): nonlocal q q = 1 print(a() is None) True but you prompted me to google: $ python3.3 -c $'def a():\n def b():\n nonlocal q\n q = 1\nprint(a() is None)' True -- https://mail.python.org/mailman/listinfo/python-list
Re: python -c commands on windows.
Terry Reedy wrote:
Manual says -c command
Execute the Python code in command. command can be one or more
statements separated by newlines, with significant leading whitespace as
in normal module code.
In Windows Command Prompt I get:
C:\Programs\Python33python -c a=1\nprint(a)
File string, line 1
a=1\nprint(a)
^
SyntaxError: unexpected character after line continuation character
(Same if I remove quotes.)
How do I get this to work?
From the odd workarounds department (not tested on Windows):
$ python3 -c exec('a=1\nprint(a)')
1
--
https://mail.python.org/mailman/listinfo/python-list
Re: Python was designed (was Re: Multi-threading in Python vs Java)
Roy Smith r...@panix.com writes: You missed the ever-so-special Objective C syntax: [object method arg1 withSomething arg2 withSomethingElse arg3] I'm sure I got that slightly wrong. I don't do Objective C, and my eyes glaze over every time I have to read it. The actual syntax would be [object method: arg1 withSomething: arg2 withSomethingElse: arg3] and IMHO once you train your eyes the result is very readable, and closely resembles Python's keywords (and I took advantage of the similarity when I enjoyed developing PyObjC :) ciao, lele. -- nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia. l...@metapensiero.it | -- Fortunato Depero, 1929. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python was designed (was Re: Multi-threading in Python vs Java)
rusi said : You continue to not attribute quotes. Sorry, I'll try to be better about this all-important aspect of sharing knowledge. -- https://mail.python.org/mailman/listinfo/python-list
Re: Animated PNG Vs Gif: 120fr 3D Python Powered Logo
On Mon, Oct 21, 2013 at 11:28 PM, Metallicow metaliobovi...@gmail.com wrote: Here is links to the apng/gif on ImageShack uploaded with the Do Not Resize option. Checked/Views fine with default Firefox/Opera browsers. Animated 3D Python Powered Logo apng - 120frames 1/60 sec http://img34.imageshack.us/img34/4717/f4l4.png gif - 120frames about 1/10sec or as fast as it can go... http://img35.imageshack.us/img35/4231/j29.gif This is not entirely true. The minimum specifiable delay for a frame in an animated gif (other than 0, which just means as fast as possible) is 0.01 second, which is the setting in the gif linked above. However, most browsers that encounter this will automatically increase the delay to 0.1 second. This is done for compatibility with old versions of Netscape. According to [1], Firefox, Opera and Chrome will accurately display delays as small as 0.02 seconds. Safari and IE will accurately display delays as small as 0.06 seconds. Here is an alternate version of the above gif that displays the animation at 50 fps in the first three browsers listed above: http://i216.photobucket.com/albums/cc41/Peristarkawan/j29-2.gif And here it is at 17 fps with 2/3 of the frames removed, for the benefit of IE and Safari: http://i216.photobucket.com/albums/cc41/Peristarkawan/j29-6.gif [1] http://nullsleep.tumblr.com/post/16524517190/animated-gif-minimum-frame-delay-browser-compatibility -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Philip Herron herron.philip at googlemail.com writes: Its interesting a few things come up what about: exec and eval. I didn't really have a good answer for this at my talk at PYCon IE 2013 but i am going to say no. I am not going to implement these. Partly because eval and exec at least to me are mostly from developing interpreters as a debugging exercise so the test doesn't have to invoke the program properly and feed in strings to interpret at least thats what i have done in the past with an virtual machine i wrote before gccpy. If you don't implement exec() and eval() then people won't be able to use namedtuples, which are a common datatype factory. As for the rest: well, good luck writing an AOT compiler producing interesting results on average *pure* Python code. It's already been tried a number of times, and has generally failed. Cython mitigates the issue by exposing a superset of Python (including type hints, etc.). Regards Antoine. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tuesday, 22 October 2013 09:55:15 UTC+1, Antoine Pitrou wrote: Philip Herron herron.philip at googlemail.com writes: Its interesting a few things come up what about: exec and eval. I didn't really have a good answer for this at my talk at PYCon IE 2013 but i am going to say no. I am not going to implement these. Partly because eval and exec at least to me are mostly from developing interpreters as a debugging exercise so the test doesn't have to invoke the program properly and feed in strings to interpret at least thats what i have done in the past with an virtual machine i wrote before gccpy. If you don't implement exec() and eval() then people won't be able to use namedtuples, which are a common datatype factory. As for the rest: well, good luck writing an AOT compiler producing interesting results on average *pure* Python code. It's already been tried a number of times, and has generally failed. Cython mitigates the issue by exposing a superset of Python (including type hints, etc.). Regards Antoine. Thanks for that interesting example, i haven't looked into how its implemented but on initially looking at this is am nearly sure i can implement this without using exec or eval. I've found this a lot in implementing my run time. Exec and eval at least to me in the past I've used them as debug hooks into a toy virtual machine i wrote i don't particularly think they are part of a language nor should people really use them. Thanks -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22 October 2013 00:41, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
On Mon, 21 Oct 2013 10:55:10 +0100, Oscar Benjamin wrote:
On 21 October 2013 08:46, Steven D'Aprano st...@pearwood.info wrote:
On the contrary, you have that backwards. An optimizing JIT compiler
can often produce much more efficient, heavily optimized code than a
static AOT compiler, and at the very least they can optimize different
things than a static compiler can. This is why very few people think
that, in the long run, Nuitka can be as fast as PyPy, and why PyPy's
ultimate aim to be faster than C is not moonbeams:
That may be true but both the examples below are spurious at best. A
decent AOT compiler would reduce both programs to the NULL program as
noted by haypo:
http://morepypy.blogspot.co.uk/2011/02/pypy-faster-than-c-on-carefully-
crafted.html?showComment=1297205903746#c2530451800553246683
Are you suggesting that gcc is not a decent compiler?
No.
If optimize away
to the null program is such an obvious thing to do, why doesn't the most
popular C compiler in the [FOSS] world do it?
It does if you pass the appropriate optimisation setting (as shown in
haypo's comment). I should have been clearer.
gcc compiles programs in two phases: compilation and linking.
Compilation creates the object files x.o and y.o from x.c and y.c.
Linking creates the output binary a.exe from x.o and y.o. The -O3
optimisation setting used in the blog post enables optimisation in the
compilation phase. However each .c file is compiled independently so
because the add() function is defined in x.c and called in y.c the
compiler is unable to inline it. It also can't remove it as dead code
because although it knows that the return value isn't used it doesn't
know if the call has side effects.
You might think it's silly that gcc can't optimise across source files
and if so you're right because actually it can if you enable link time
optimisation with the -flto flag as described by haypo. So if I do
that with the code from the blog post I get (using mingw gcc 4.7.2 on
Windows):
$ cat x.c
double add(double a, double b)
{
return a + b;
}
$ cat y.c
double add(double a, double b);
int main()
{
int i = 0;
double a = 0;
while (i 10) {
a += 1.0;
add(a, a);
i++;
}
}
$ gcc -O3 -flto x.c y.c
$ time ./a.exe
real0m0.063s
user0m0.015s
sys 0m0.000s
$ time ./a.exe # warm cache
real0m0.016s
user0m0.015s
sys 0m0.015s
So gcc can optimise this all the way to the null program which takes
15ms to run (that's 600 times faster than pypy).
Note that even if pypy could optimise it all the way to the null
program it would still be 10 times slower than C's null program:
$ touch null.py
$ time pypy null.py
real0m0.188s
user0m0.076s
sys 0m0.046s
$ time pypy null.py # warm cache
real0m0.157s
user0m0.060s
sys 0m0.030s
[...]
So the pypy version takes twice as long to run this. That's impressive
but it's not faster than C.
(Actually if I enable -flts with that example the C version runs 6-7
times faster due to inlining.)
Nobody is saying that PyPy is *generally* capable of making any arbitrary
piece of code run as fast as hand-written C code. You'll notice that the
PyPy posts are described as *carefully crafted* examples.
They are more than carefully crafted. They are useless and misleading.
It's reasonable to contrive of a simple CPU-intensive programming
problem for benchmarking. But the program should do *something* even
if it is contrived. Both programs here consist *entirely* of dead
code. Yes it's reasonable for the pypy devs to test things like this
during development. No it's not reasonable to showcase this as an
example of the potential for pypy to speed up any useful computation.
I believe that, realistically, PyPy has potential to bring Python into
Java and .Net territories, namely to run typical benchmarks within an
order of magnitude of C speeds on the same benchmarks. C is a very hard
target to beat, because vanilla C code does *so little* compared to other
languages: no garbage collection, no runtime dynamism, very little
polymorphism. So benchmarking simple algorithms plays to C's strengths,
while ignoring C's weaknesses.
As I said I don't want to criticise PyPy. I've just started using it
and I it is impressive. However both of those blog posts are
misleading. Not only that but the authors must know exactly why they
are misleading. Because of that I will take any other claims with a
big pinch of salt in future.
Oscar
--
https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tuesday, 22 October 2013 10:14:16 UTC+1, Oscar Benjamin wrote:
On 22 October 2013 00:41, Steven D'Aprano
On the contrary, you have that backwards. An optimizing JIT compiler
can often produce much more efficient, heavily optimized code than a
static AOT compiler, and at the very least they can optimize different
things than a static compiler can. This is why very few people think
that, in the long run, Nuitka can be as fast as PyPy, and why PyPy's
ultimate aim to be faster than C is not moonbeams:
That may be true but both the examples below are spurious at best. A
decent AOT compiler would reduce both programs to the NULL program as
noted by haypo:
http://morepypy.blogspot.co.uk/2011/02/pypy-faster-than-c-on-carefully-
crafted.html?showComment=1297205903746#c2530451800553246683
Are you suggesting that gcc is not a decent compiler?
No.
If optimize away
to the null program is such an obvious thing to do, why doesn't the most
popular C compiler in the [FOSS] world do it?
It does if you pass the appropriate optimisation setting (as shown in
haypo's comment). I should have been clearer.
gcc compiles programs in two phases: compilation and linking.
Compilation creates the object files x.o and y.o from x.c and y.c.
Linking creates the output binary a.exe from x.o and y.o. The -O3
optimisation setting used in the blog post enables optimisation in the
compilation phase. However each .c file is compiled independently so
because the add() function is defined in x.c and called in y.c the
compiler is unable to inline it. It also can't remove it as dead code
because although it knows that the return value isn't used it doesn't
know if the call has side effects.
You might think it's silly that gcc can't optimise across source files
and if so you're right because actually it can if you enable link time
optimisation with the -flto flag as described by haypo. So if I do
that with the code from the blog post I get (using mingw gcc 4.7.2 on
Windows):
$ cat x.c
double add(double a, double b)
{
return a + b;
}
$ cat y.c
double add(double a, double b);
int main()
{
int i = 0;
double a = 0;
while (i 10) {
a += 1.0;
add(a, a);
i++;
}
}
$ gcc -O3 -flto x.c y.c
$ time ./a.exe
real0m0.063s
user0m0.015s
sys 0m0.000s
$ time ./a.exe # warm cache
real0m0.016s
user0m0.015s
sys 0m0.015s
So gcc can optimise this all the way to the null program which takes
15ms to run (that's 600 times faster than pypy).
Note that even if pypy could optimise it all the way to the null
program it would still be 10 times slower than C's null program:
$ touch null.py
$ time pypy null.py
real0m0.188s
user0m0.076s
sys 0m0.046s
$ time pypy null.py # warm cache
real0m0.157s
user0m0.060s
sys 0m0.030s
[...]
So the pypy version takes twice as long to run this. That's impressive
but it's not faster than C.
(Actually if I enable -flts with that example the C version runs 6-7
times faster due to inlining.)
Nobody is saying that PyPy is *generally* capable of making any arbitrary
piece of code run as fast as hand-written C code. You'll notice that the
PyPy posts are described as *carefully crafted* examples.
They are more than carefully crafted. They are useless and misleading.
It's reasonable to contrive of a simple CPU-intensive programming
problem for benchmarking. But the program should do *something* even
if it is contrived. Both programs here consist *entirely* of dead
code. Yes it's reasonable for the pypy devs to test things like this
during development. No it's not reasonable to showcase this as an
example of the potential for pypy to speed up any useful computation.
I believe that, realistically, PyPy has potential to bring Python into
Java and .Net territories, namely to run typical benchmarks within an
order of magnitude of C speeds on the same benchmarks. C is a very hard
target to beat, because vanilla C code does *so little* compared to other
languages: no garbage collection, no runtime dynamism, very little
polymorphism. So benchmarking simple algorithms plays to C's strengths,
while ignoring C's weaknesses.
As I said I don't want to criticise PyPy. I've just started using it
and I it is impressive. However both of those blog posts are
misleading. Not only that but the authors must know exactly why they
are misleading. Because of that I will take any other claims with a
big pinch of salt in future.
Oscar
You sir deserve a medal! I think alot of people are taking these sorts of
benchmarks completely out of context and its great to see such a well rounded
Re: Python Front-end to GCC
On Tue, 22 Oct 2013 08:55:15 +, Antoine Pitrou wrote: If you don't implement exec() and eval() then people won't be able to use namedtuples, which are a common datatype factory. Philip could always supply his own implementation of namedtuple that doesn't use exec. But either way, if he doesn't implement eval and exec, what he has is not Python, but a subset of Python. Perhaps an interesting and useful subset. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: python -c commands on windows.
On 21 October 2013 21:47, Terry Reedy tjre...@udel.edu wrote: Manual says -c command Execute the Python code in command. command can be one or more statements separated by newlines, with significant leading whitespace as in normal module code. In Windows Command Prompt I get: C:\Programs\Python33python -c a=1\nprint(a) File string, line 1 a=1\nprint(a) ^ SyntaxError: unexpected character after line continuation character (Same if I remove quotes.) How do I get this to work? By not using cmd.exe. On Windows I use git bash which I think is just bash from msys. If you find yourself spending any time using cmd.exe you'll appreciate why. I also use console2 as the GUI part of the terminal. In bash it's a simple matter of opening a single quote and then typing what you want including hitting enter (don't use single quotes in the Python code): $ python -c ' a = 1 if a: print(a was true) ' a was true Oscar -- https://mail.python.org/mailman/listinfo/python-list
Re: python -c commands on windows.
On Tue, Oct 22, 2013 at 9:42 PM, Oscar Benjamin oscar.j.benja...@gmail.com wrote: On Windows I use git bash which I think is just bash from msys. If you find yourself spending any time using cmd.exe you'll appreciate why. I also use console2 as the GUI part of the terminal. Heh, me too. According to its title bar, it's a MINGW32 build (or at least, the one I have is). I installed nano into it, and I can basically run my git repos the same way I do under Linux. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Python was designed (was Re: Multi-threading in Python vs Java)
Steven wrote: The world is much bigger than just the C family of languages. And even within that space, the original authors of C left plenty of room for debate/improvement. In at least two dimensions (object oriented programming, and memory management), various C descendants have tried multiple different approaches to solve those problems. Skip -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, 22 Oct 2013 10:14:16 +0100, Oscar Benjamin wrote: On 22 October 2013 00:41, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Mon, 21 Oct 2013 10:55:10 +0100, Oscar Benjamin wrote: On 21 October 2013 08:46, Steven D'Aprano st...@pearwood.info wrote: On the contrary, you have that backwards. An optimizing JIT compiler can often produce much more efficient, heavily optimized code than a static AOT compiler, and at the very least they can optimize different things than a static compiler can. This is why very few people think that, in the long run, Nuitka can be as fast as PyPy, and why PyPy's ultimate aim to be faster than C is not moonbeams: That may be true but both the examples below are spurious at best. A decent AOT compiler would reduce both programs to the NULL program as noted by haypo: http://morepypy.blogspot.co.uk/2011/02/pypy-faster-than-c-on- carefully- crafted.html?showComment=1297205903746#c2530451800553246683 Keep in mind that the post's author, Maciej Fijalkowski, is not a native English speaker (to the best of my knowledge). You or I would probably have called the post a *contrived* example, not a carefully crafted one -- the meaning is the same, but the connotations are different. Micro-benchmarks are mostly of theoretical interest, and contrived ones even more so, but still of interest. One needs to be careful not to read too much into them, but also not to read too little into them. Are you suggesting that gcc is not a decent compiler? No. If optimize away to the null program is such an obvious thing to do, why doesn't the most popular C compiler in the [FOSS] world do it? It does if you pass the appropriate optimisation setting (as shown in haypo's comment). I should have been clearer. C can do nothing 10 times faster than Python! -- well, okay, but what does that tell you about my long-running web server app? Benchmarks at the best of time are only suggestive, benchmarks for null programs are even less useful. The very next comment after Haypo is an answer to his observation: [quote] @haypo print the result so the loop don't get removed as dead code. Besides, the problem is really the fact that's -flto is unfair since python imports more resemble shared libraries than statically-compiled files. I'll be honest, I don't know enough C to really judge that claim, but I have noticed that benchmarks rarely compare apples and oranges, especially when C is involved. You can't eliminate all the differences between the code being generated, or at least not easily, since different languages have deep-seated differences in semantics that can't be entirely eliminated. But you should at least make some effort to compare code that does the same thing the same way. Here's an example: responding to a benchmark showing a Haskell compiler generating faster code than a C compiler, somebody re-wrote the C code and got the opposite result: http://jacquesmattheij.com/when-haskell-is-not-faster-than-c Again, I can't judge the validity of all of the changes he made, but one stood out like a sore thumb: [quote] C does not require you to set static global arrays to ‘0’, so the for loop in the main function can go... Wait a minute... Haskell, I'm pretty sure, zeroes memory. C doesn't. So the C code is now doing less work. Yes, your C compiler will allow you to avoid zeroing memory before using it, and you'll save some time initially. But eventually[1] you will need to fix the security vulnerability by adding code to zero the memory, exactly as Haskell and other more secure languages already do. So *not* zeroing the memory is cheating. It's not something you'd do in real code, not if you care about security and correctness. Even if you don't care about security, you should care about benchmarking both languages performing the same amount of work. Now, I may be completely off-base here. Some Haskell expert may chime up to say that Haskell does not, in fact, zero memory. But it does *something*, I'm sure, perhaps it tracks what memory is undefined and prevents reads from it, or something. Whatever it does, if it does it at runtime, the C benchmark better do the same thing, or it's an unfair comparison: Safely drive to the mall obeying all speed limits and traffic signals in a Chevy Volt, versus speed down the road running red lights and stop signs in a Ford Taurus -- would it be any surprise that the Taurus is faster? [...] They are more than carefully crafted. They are useless and misleading. It's reasonable to contrive of a simple CPU-intensive programming problem for benchmarking. But the program should do *something* even if it is contrived. Both programs here consist *entirely* of dead code. But since the dead code is *not* eliminated, it is actually executed. If it's executed, it's not really dead, is it? Does it really matter that you don't do anything with the
Re: Python Front-end to GCC
On Tue, Oct 22, 2013 at 11:00 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Given a sufficiently advanced static analyser, PyPy could probably special-case programs that do nothing. Then you're in a race to compare the speed at which the PyPy runtime environment can start up and do nothing, versus a stand-alone executable that has to start up and do nothing. If this is a benchmark that people care about, I suggest they need to get out more :-) Like every benchmark, it has its uses. Just last week I was tinkering with several high level languages in order to see which one would start, do a fairly trivial task, and shut down, in the shortest space of time. Why? Because I wanted that trivial task to be added to our rapid-deployment sequence at a point where a human would be waiting on it, and the task itself wasn't critical (it was an early-catcher for a particular type of bug). Delaying my fellow developers by even one second at that point would be unacceptable; the various options at my disposal took anywhere from 250 to 750 ms (cold cache, which is what matters) to run. Yes, I know a second isn't long. But I was trying to sell a concept, and if I can say that it adds practically no time to an interactive action, that's a lot better than even one second. Considering that rapiding took about 1200ms (ish - again, cold cache) previously, adding even just 250ms is noticeable. Benchmarking an empty program would get very close to this actual real-world scenario. (Eventually I merged the functionality into an unrelated script just for the sake of saving on interpreter startup time.) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
PY QT
I'm really embarrassed to be asking this, I feel that there is a really simple answer to this, but I cant for the life of me find it. So, I have this app, which loads a ui, which has a scrollarea that is a parent to a gridlayout. So in QT designer it looks like this: /someParentWidgets scrollArea myGridLayout/ I then want to add a couple of Qtool buttons to the GridLayout within my python code, so i run a forloop: /for name in mylist: btn =QtGui.QToolButton() btn.setText(str(name)) cols = self.myGridLayout.count()%6 rows = int(self.myGridLayout.count()/6) self.myGridLayout.addWidget(btn,rows,cols)/ No errors, no complaining what so ever, but the buttons isn't showing in the layout. The thing is if I change my ui file to /someParentWidgets myGridLayout / The buttons show perfectly fine! What am I missing? I've tried changing the GridLayout to a verticalLayout, but same thing there... -- View this message in context: http://python.6.x6.nabble.com/PY-QT-tp5036684.html Sent from the Python - python-list mailing list archive at Nabble.com. -- https://mail.python.org/mailman/listinfo/python-list
pip won't ignore system-installed files
IIUC, it is perfectly legitimate to do install into --user to override system- wide installed modules. Thus, I should be able to do: pip install --user --up blah even though there is already a package blah in /usr/lib/pythonxxx/site_packages/... But even with -I (ignore installed) switch, pip fails: pip install --user --up -I matplotlib ... Installing collected packages: matplotlib, numpy, python-dateutil, tornado, pyparsing, nose, six Found existing installation: matplotlib 1.2.0 Uninstalling matplotlib: Exception: Traceback (most recent call last): File /usr/lib/python2.7/site-packages/pip-1.2.1- py2.7.egg/pip/basecommand.py, line 107, in main status = self.run(options, args) File /usr/lib/python2.7/site-packages/pip-1.2.1- py2.7.egg/pip/commands/install.py, line 261, in run requirement_set.install(install_options, global_options) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/req.py, line 1162, in install requirement.uninstall(auto_confirm=True) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/req.py, line 495, in uninstall paths_to_remove.remove(auto_confirm) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/req.py, line 1492, in remove renames(path, new_path) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/util.py, line 273, in renames shutil.move(old, new) File /usr/lib64/python2.7/shutil.py, line 302, in move os.unlink(src) OSError: [Errno 13] Permission denied: '/usr/lib64/python2.7/site- packages/matplotlib-1.2.0-py2.7.egg-info' Can we please fix this? -- https://mail.python.org/mailman/listinfo/python-list
Re: pip won't ignore system-installed files
On Tue, Oct 22, 2013 at 8:11 AM, Neal Becker ndbeck...@gmail.com wrote: IIUC, it is perfectly legitimate to do install into --user to override system- wide installed modules. Thus, I should be able to do: pip install --user --up blah even though there is already a package blah in /usr/lib/pythonxxx/site_packages/... ... Can we please fix this? Sounds like a job for a bug report (for pip, most likely), not so much a post to comp.lang.python. What happens if you omit --upgrade? Skip -- https://mail.python.org/mailman/listinfo/python-list
Re: PY QT
Le 22/10/2013 15:01, Forsgren a écrit : I'm really embarrassed to be asking this, I feel that there is a really simple answer to this, but I cant for the life of me find it. So, I have this app, which loads a ui, which has a scrollarea that is a parent to a gridlayout. So in QT designer it looks like this: /someParentWidgets scrollArea myGridLayout/ I then want to add a couple of Qtool buttons to the GridLayout within my python code, so i run a forloop: /for name in mylist: btn =QtGui.QToolButton() btn.setText(str(name)) cols = self.myGridLayout.count()%6 rows = int(self.myGridLayout.count()/6) self.myGridLayout.addWidget(btn,rows,cols)/ No errors, no complaining what so ever, but the buttons isn't showing in the layout. The thing is if I change my ui file to /someParentWidgets myGridLayout / The buttons show perfectly fine! What am I missing? I've tried changing the GridLayout to a verticalLayout, but same thing there... -- View this message in context: http://python.6.x6.nabble.com/PY-QT-tp5036684.html Sent from the Python - python-list mailing list archive at Nabble.com. Why are you using % 6 on QLayout.count() ? QLayout.count() returns the number of the items into the layout but not where are is. If you want to know the number of rows and columns, you have rowCount() and columnCount(). Cheers -- Vincent V.V. Oqapy https://launchpad.net/oqapy . Qarte https://launchpad.net/qarte . PaQager https://launchpad.net/paqager -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 08:00, Steven D'Aprano wrote: On Tue, 22 Oct 2013 10:14:16 +0100, Oscar Benjamin wrote: snip Here's an example: responding to a benchmark showing a Haskell compiler generating faster code than a C compiler, somebody re-wrote the C code and got the opposite result: http://jacquesmattheij.com/when-haskell-is-not-faster-than-c Again, I can't judge the validity of all of the changes he made, but one stood out like a sore thumb: [quote] C does not require you to set static global arrays to ‘0’, so the for loop in the main function can go... Wait a minute... Haskell, I'm pretty sure, zeroes memory. C doesn't. So Static int variables are in fact zeroed. However, most C compilers do it by putting four bytes (or whatever) into the image of the executable so it has no runtime cost. snip But eventually[1] you will need to fix the security vulnerability by adding code to zero the memory, exactly as Haskell and other more secure languages already do. So *not* zeroing the memory is cheating. It's not something you'd do in real code, not if you care about security and correctness. I agree with most of what you say in the message, but here you go on to say the C code is unsafely skipping initialization, which is not the case. By the way, a C compiler typically handles any initialization of a static variable the same way. So if you declare and initialize a static variable as int myvar = 34 * 768; it'll put the product directly in the executable image, and no runtime code is generated. Perhaps you were thinking of an automatic variable, which is not initialized unless the programmer says so, and is then initialized with code. -- DaveA -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22 October 2013 13:00, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
On Tue, 22 Oct 2013 10:14:16 +0100, Oscar Benjamin wrote:
On 22 October 2013 00:41, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
Are you suggesting that gcc is not a decent compiler?
No.
If optimize away
to the null program is such an obvious thing to do, why doesn't the
most popular C compiler in the [FOSS] world do it?
It does if you pass the appropriate optimisation setting (as shown in
haypo's comment). I should have been clearer.
C can do nothing 10 times faster than Python! -- well, okay, but what
does that tell you about my long-running web server app? Benchmarks at
the best of time are only suggestive, benchmarks for null programs are
even less useful.
This is precisely my point. They should show a benchmark that is not
semantically equivalent to the null program. I modified their example
to do that so that it wasn't simply a case of removing dead code and
then found that the C version performed 6-7 times faster than the PyPy
version. Had they simply stated that I would have been impressed.
At the bottom of this post I show a much better benchmark that shows
how PyPy can come very close to C performance for intensive floating
point computation. Note that although it is simple the benchmark
actually produces a result and none of the computation can be skipped
as dead code (why would I put that in?). Also note that both the C
binary and the script produce exactly the same numeric output. It's
also a simple example of numerical integration - something that is
often a bottleneck in scientific computation.
For the benchmark I find that the gcc -O3 binary runs in 4.6s and PyPy
runs the script in 6.9s (CPython 2.7 takes 600 seconds). That is
impressive and makes me think that there may be no need for me to use
C for things like that. To be sure I'd have to scale it up a bit to
see what happens when I break it apart into many functions and use
lists in PyPy vs arrays in C.
[...]
They are more than carefully crafted. They are useless and misleading.
It's reasonable to contrive of a simple CPU-intensive programming
problem for benchmarking. But the program should do *something* even if
it is contrived. Both programs here consist *entirely* of dead code.
But since the dead code is *not* eliminated, it is actually executed. If
it's executed, it's not really dead, is it? Does it really matter that
you don't do anything with the result? I'm with Maciej on this one --
*executing* the code given is faster in PyPy than in C, at least for this
C compiler. Maybe C is faster to not execute it. Is that really an
interesting benchmark? C does nothing ten times faster than PyPy does
something!
I don't think it is reasonable to compare those things and I was
joking when I said that the optimised C version was 600 times faster
because this is an absurd benchmark - see the much better one below.
Given a sufficiently advanced static analyser, PyPy could probably
special-case programs that do nothing. Then you're in a race to compare
the speed at which the PyPy runtime environment can start up and do
nothing, versus a stand-alone executable that has to start up and do
nothing. If this is a benchmark that people care about, I suggest they
need to get out more :-)
Like Chris I have also had situations where startup time mattered and
it can vary substantially between different interpreters and binaries.
I have GNU Octave on Windows and it literally takes 20 seconds to
start up. Matlab is worse: it takes about 1 minute so I don't tend to
use it for CLI scripts much.
Oscar
The benchmark:
$ cat euler.py
#!/usr/bin/env pypy
import math
def main():
x = 1
v = 0
t = 0
T = 1
dt = 2**-30
while t T:
dxdt = v
dvdt = - x
x += dt * dxdt
v += dt * dvdt
t += dt
print('t = %.2e' % t)
print('x = %.2e' % x)
print('v = %.2e' % v)
print('x_err = %.e' % (x - math.cos(t)))
print('x_err = %.2e' % (v + math.sin(t)))
main()
$ time pypy euler.py
t = 1.00e+00
x = 5.40e-01
v = -8.41e-01
x_err = 3e-10
x_err = -3.92e-10
real0m6.907s
user0m0.076s
sys 0m0.045s
$ cat euler.c
#include stdio.h
#include math.h
int main()
{
double x = 1;
double v = 0;
double t = 0;
double T = 1;
double dt = pow(2, -30);
double dxdt, dvdt;
while (t T)
{
dxdt = v;
dvdt = - x;
x += dt * dxdt;
v += dt * dvdt;
t += dt;
}
printf(t = %.2e\n, t);
printf(x = %.2e\n, x);
printf(v = %.2e\n, v);
printf(x_err = %.e\n, x - cos(t));
printf(x_err = %.2e\n, v + sin(t));
return 0;
}
$ gcc -O3 euler.c
$ time ./a.exe
t = 1.00e+000
x = 5.40e-001
v = -8.41e-001
x_err = 3e-010
x_err = -3.92e-010
real0m4.609s
user0m0.015s
sys 0m0.000s
$ time python euler.py # CPython 2.7
t = 1.00e+00
x = 5.40e-01
v = -8.41e-01
x_err = 3e-10
x_err =
Re: Animated PNG Vs Gif: 120fr 3D Python Powered Logo
On Tuesday, October 22, 2013 2:56:33 AM UTC-5, Ian wrote: This is not entirely true. The minimum specifiable delay for a frame in an animated gif (other than 0, which just means as fast as possible) is 0.01 second, which is the setting in the gif linked above. However, most browsers that encounter this will automatically increase the delay to 0.1 second. This is done for compatibility with old versions of Netscape. According to [1], Firefox, Opera and Chrome will accurately display delays as small as 0.02 seconds. Safari and IE will accurately display delays as small as 0.06 seconds. Here is an alternate version of the above gif that displays the animation at 50 fps in the first three browsers listed above: http://i216.photobucket.com/albums/cc41/Peristarkawan/j29-2.gif And here it is at 17 fps with 2/3 of the frames removed, for the benefit of IE and Safari: http://i216.photobucket.com/albums/cc41/Peristarkawan/j29-6.gif [1] http://nullsleep.tumblr.com/post/16524517190/animated-gif-minimum-frame-delay-browser-compatibility Thanks, I was having a bit of trouble trying to figure it out exactly myself in blender by eye-sight. Interesting Test link. When I originally rendered the animation it was transparent background, but when giffed it looked rather sick with gifs limited transparency and colors specs, so I rerendered and modded the text back into it on white which is what the other PSF logos have. After looking at Firefox's spinning fox APNG on transparent, I think I will rerender the images again with transparency for the apng, so background color can be easily changed. It seems the delays are not altered on the apngs also, which is a good thing. Maybe there is an option with the browsers to disable gif 0 delay mangling...? So What did you use to increase the speed of the gif? ...Errm Program or whatever used to mod it? I made the gif with gimp, since I find importing/exporting as layers a bit easier than using imageready. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
I love it. Watch this... [context] A language specification in BNF is just syntax. It doesn't say anything about semantics. So how could this be used to produce executable C code for a program? BNF is used to produce parsers. But a parser isn't sufficient. A C program is just syntax also. How does the compiler generate executable machine code? Extrapolate into a Python front-end to C. [Dave Angel responds:] Did you even read the paragraph you quoted above? The BNF specification does NOT completely describe a language, it only defines its syntax. [Steven D'Aprano responds:] Like every other language, C programs are certainly not *just* syntax. Here is some syntax: foo bar^ := Now, I don't know where y'all were taught Computer Science, but BNF specifies not only syntax (which would be the *tokens* of a language), but also its *grammar*; how syntax relates to linguistic categories like keywords, and tokens relate to each other. Dave is claiming that BNF only defines the syntax of a language, but then Stephen goes on to supply some syntax that a BNF specification of the language would not allow (even though Steven calls it syntax which is what BNF in Dave's claim parses). So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Mark Janssen Tacoma, Washington. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, 22 Oct 2013 14:04:57 +, Dave Angel wrote: [...] I agree with most of what you say in the message, Glad to hear I wasn't completely full of it. As a non-C developer, I'm very conscious that a lot of what I know about C is second hand. but here you go on to say the C code is unsafely skipping initialization, which is not the case. Are you talking generically, or specifically about the C code referenced in the link I gave? Memory is always zeroed is one of the advantages of Go over C and C++, at least according to Rob Pike: http://commandcenter.blogspot.com.au/2012/06/less-is-exponentially- more.html By the way, a C compiler typically handles any initialization of a static variable the same way. So if you declare and initialize a static variable as int myvar = 34 * 768; it'll put the product directly in the executable image, and no runtime code is generated. Yes, that's a keyhole optimization, CPython does the same sort of thing: py import dis py dis.dis(compile(myvar = 34 * 768, , exec)) 1 0 LOAD_CONST 3 (26112) 3 STORE_NAME 0 (myvar) 6 LOAD_CONST 2 (None) 9 RETURN_VALUE Perhaps you were thinking of an automatic variable, which is not initialized unless the programmer says so, and is then initialized with code. No, I was thinking of an array. Arrays aren't automatically initialised in C. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Dave Angel da...@davea.name wrote: On 22/10/2013 08:00, Steven D'Aprano wrote: [quote] C does not require you to set static global arrays to ?0?, so the for loop in the main function can go... Wait a minute... Haskell, I'm pretty sure, zeroes memory. C doesn't. So Static int variables are in fact zeroed. However, most C compilers do it by putting four bytes (or whatever) into the image of the executable so it has no runtime cost. No, that's not how gcc works (nor is it how any other C compiler I've ever seen works). Static variables get located in a bss section[1], which is zeroed out at run-time by startup code that gets executed before main() is called. The ELF executable contains headers that describe the size/location of bss section, but the object file contains no actual _data_. [1] IIRC, the name bss is a historical hold-over from the PDP-11 assembler directive that is used to declare a section of memory that is to be filled with zeros. Not all compilers use that section name, but they all use the same mechanism. int myvar = 34 * 768; it'll put the product directly in the executable image, and no runtime code is generated. That is true. -- Grant Edwards grant.b.edwardsYow! My EARS are GONE!! at gmail.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Tue, 22 Oct 2013 14:04:57 +, Dave Angel wrote: [...] I agree with most of what you say in the message, Glad to hear I wasn't completely full of it. As a non-C developer, I'm very conscious that a lot of what I know about C is second hand. but here you go on to say the C code is unsafely skipping initialization, which is not the case. Are you talking generically, or specifically about the C code referenced in the link I gave? In C, static/global variables are always zeroed. Memory is always zeroed is one of the advantages of Go over C and C++, at least according to Rob Pike: http://commandcenter.blogspot.com.au/2012/06/less-is-exponentially-more.html Perhaps he's talking about automatic variables or malloc()ed memory? You'd have to ask him. Perhaps you were thinking of an automatic variable, which is not initialized unless the programmer says so, and is then initialized with code. No, I was thinking of an array. Arrays aren't automatically initialised in C. If they are static or global, then _yes_they_are_. They are zeroed. -- Grant Edwards grant.b.edwardsYow! I selected E5 ... but at I didn't hear Sam the Sham gmail.comand the Pharoahs! -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 10/22/13 11:04 AM, Mark Janssen wrote: I love it. Watch this... [context] A language specification in BNF is just syntax. It doesn't say anything about semantics. So how could this be used to produce executable C code for a program? BNF is used to produce parsers. But a parser isn't sufficient. A C program is just syntax also. How does the compiler generate executable machine code? Extrapolate into a Python front-end to C. [Dave Angel responds:] Did you even read the paragraph you quoted above? The BNF specification does NOT completely describe a language, it only defines its syntax. [Steven D'Aprano responds:] Like every other language, C programs are certainly not *just* syntax. Here is some syntax: foo bar^ := Now, I don't know where y'all were taught Computer Science, but BNF specifies not only syntax (which would be the *tokens* of a language), but also its *grammar*; how syntax relates to linguistic categories like keywords, and tokens relate to each other. Mark, you had expressed interest in an app that will take a language specification in BNF (complete with keywords and all) and output C code which is then compiled to an executable. I'm interested in how that app might work. Here's a BNF for a (very!) simple language: program ::= number op number op ::= *!? | --+ | ..: That means these are three valid programs: 123 *!? 456 2 --+ 2 1001 ..: 4 What will the app output as C code for each of these? Dave is claiming that BNF only defines the syntax of a language, but then Stephen goes on to supply some syntax that a BNF specification of the language would not allow (even though Steven calls it syntax which is what BNF in Dave's claim parses). So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Could you please be less snarky? We're trying to communicate here, and it is not at all clear yet who is confused and who is not. If you are interested in discussing technical topics, then discuss them. --Ned. Mark Janssen Tacoma, Washington. -- https://mail.python.org/mailman/listinfo/python-list
Re: Class construction
On 2013-10-21, Marcin Szamotulski msza...@gmail.com wrote: So the process (with some simplifications) goes like this: 1. get metaclass: meta 2. call meta.__prepare__ to get namespace (class __dict__) 3. evaluate the class body in the namespace 4. call meta with arguemnts: name, bases, namespace (when you instantiate any class in Python, metaclass is just a class, first its __new__ method is called, and then its __init__) All this is in builtin__build_class__. In addition, the Python manual describes the process in detail. See The Python Language Reference 8.7 Class definitions. Here's a link to the 3.3 version of those docs: http://docs.python.org/3.3/reference/compound_stmts.html#class-definitions -- Neil Cerutti -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Steven D'Aprano steve+comp.lang.python at pearwood.info writes: On Tue, 22 Oct 2013 08:55:15 +, Antoine Pitrou wrote: If you don't implement exec() and eval() then people won't be able to use namedtuples, which are a common datatype factory. Philip could always supply his own implementation of namedtuple that doesn't use exec. But either way, if he doesn't implement eval and exec, what he has is not Python, but a subset of Python. Perhaps an interesting and useful subset. If you go that way, we already have Cython (which is both a subset and superset of Python, although I don't know if it's still a strict subset these days). Regards Antoine. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 16:46, Ned Batchelder wrote: Could you please be less snarky? We're trying to communicate here, and it is not at all clear yet who is confused and who is not. If you are interested in discussing technical topics, then discuss them. --Ned. Well put, particularly when considering that both Dave Angel and Steven D'Aprano, the targets of the snarkiness, have been regular, helpful contributors over many years. -- Python is the second best programming language in the world. But the best has yet to be invented. Christian Tismer Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, Oct 22, 2013 at 8:04 AM, Mark Janssen dreamingforw...@gmail.com wrote: I love it. Watch this... [context] A language specification in BNF is just syntax. It doesn't say anything about semantics. So how could this be used to produce executable C code for a program? BNF is used to produce parsers. But a parser isn't sufficient. A C program is just syntax also. How does the compiler generate executable machine code? Extrapolate into a Python front-end to C. [Dave Angel responds:] Did you even read the paragraph you quoted above? The BNF specification does NOT completely describe a language, it only defines its syntax. [Steven D'Aprano responds:] Like every other language, C programs are certainly not *just* syntax. Here is some syntax: foo bar^ := Now, I don't know where y'all were taught Computer Science, but BNF specifies not only syntax (which would be the *tokens* of a language), but also its *grammar*; how syntax relates to linguistic categories like keywords, and tokens relate to each other. Dave is claiming that BNF only defines the syntax of a language, but then Stephen goes on to supply some syntax that a BNF specification of the language would not allow (even though Steven calls it syntax which is what BNF in Dave's claim parses). So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. I don't know where you were taught English, but syntax is the way in which linguistic elements (as words) are put together to form constituents (as phrases or clauses) , not the set of valid words (tokens) in a language. A grammar, such as those grammars written in BNF, describe the rules for the syntax of a language. And, as Steven said, it still doesn't describe the semantics of a language, which is the set of instructions described by the syntax. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, 22 Oct 2013 15:39:42 +, Grant Edwards wrote:
No, I was thinking of an array. Arrays aren't automatically initialised
in C.
If they are static or global, then _yes_they_are_. They are zeroed.
Not that I don't believe you, but do you have a reference for this?
Because I keep finding references to uninitialised C arrays filled with
garbage if you don't initialise them.
Wait... hang on a second...
/fires up the ol' trusty gcc
[steve@ando c]$ cat array_init.c
#includestdio.h
int main()
{
int i;
int arr[10];
for (i = 0; i 10; i++) {
printf(arr[%d] = %d\n, i, arr[i]);
}
printf(\n);
return 0;
}
[steve@ando c]$ gcc array_init.c
[steve@ando c]$ ./a.out
arr[0] = -1082002360
arr[1] = 134513317
arr[2] = 2527220
arr[3] = 2519564
arr[4] = -1082002312
arr[5] = 134513753
arr[6] = 1294213
arr[7] = -1082002164
arr[8] = -1082002312
arr[9] = 2527220
What am I missing here?
--
Steven
--
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Re: Python Front-end to GCC
On 22/10/2013 17:40, Steven D'Aprano wrote:
On Tue, 22 Oct 2013 15:39:42 +, Grant Edwards wrote:
No, I was thinking of an array. Arrays aren't automatically initialised
in C.
If they are static or global, then _yes_they_are_. They are zeroed.
Not that I don't believe you, but do you have a reference for this?
Because I keep finding references to uninitialised C arrays filled with
garbage if you don't initialise them.
Wait... hang on a second...
/fires up the ol' trusty gcc
[steve@ando c]$ cat array_init.c
#includestdio.h
int main()
{
int i;
int arr[10];
for (i = 0; i 10; i++) {
printf(arr[%d] = %d\n, i, arr[i]);
}
printf(\n);
return 0;
}
[steve@ando c]$ gcc array_init.c
[steve@ando c]$ ./a.out
arr[0] = -1082002360
arr[1] = 134513317
arr[2] = 2527220
arr[3] = 2519564
arr[4] = -1082002312
arr[5] = 134513753
arr[6] = 1294213
arr[7] = -1082002164
arr[8] = -1082002312
arr[9] = 2527220
What am I missing here?
arr is local to main, not static or global.
--
Python is the second best programming language in the world.
But the best has yet to be invented. Christian Tismer
Mark Lawrence
--
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Re: Python Front-end to GCC
On Tue, Oct 22, 2013 at 9:40 AM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
On Tue, 22 Oct 2013 15:39:42 +, Grant Edwards wrote:
No, I was thinking of an array. Arrays aren't automatically initialised
in C.
If they are static or global, then _yes_they_are_. They are zeroed.
Not that I don't believe you, but do you have a reference for this?
Because I keep finding references to uninitialised C arrays filled with
garbage if you don't initialise them.
Wait... hang on a second...
/fires up the ol' trusty gcc
[steve@ando c]$ cat array_init.c
#includestdio.h
int main()
{
int i;
int arr[10];
for (i = 0; i 10; i++) {
printf(arr[%d] = %d\n, i, arr[i]);
}
printf(\n);
return 0;
}
[steve@ando c]$ gcc array_init.c
[steve@ando c]$ ./a.out
arr[0] = -1082002360
arr[1] = 134513317
arr[2] = 2527220
arr[3] = 2519564
arr[4] = -1082002312
arr[5] = 134513753
arr[6] = 1294213
arr[7] = -1082002164
arr[8] = -1082002312
arr[9] = 2527220
What am I missing here?
The array you made there is an auto variable (stack), not a static or a
global. Try one of the following (neither has been tested):
Static:
int main()
{
int i;
static int arr[10];
for (i = 0; i 10; i++) {
printf(arr[%d] = %d\n, i, arr[i]);
}
printf(\n);
return 0;
}
Global:
int arr[10];
int main()
{
int i;
for (i = 0; i 10; i++) {
printf(arr[%d] = %d\n, i, arr[i]);
}
printf(\n);
return 0;
}
As for a reference:
http://stackoverflow.com/questions/1831290/static-variable-initialization
and
http://stackoverflow.com/questions/3373108/why-are-static-variables-auto-initialized-to-zero,
both of which then reference the C++ standard.
--
Steven
--
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--
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Re: Python Front-end to GCC
On Tue, 22 Oct 2013 16:40:32 +, Steven D'Aprano wrote:
On Tue, 22 Oct 2013 15:39:42 +, Grant Edwards wrote:
No, I was thinking of an array. Arrays aren't automatically
initialised in C.
If they are static or global, then _yes_they_are_. They are zeroed.
Not that I don't believe you, but do you have a reference for this?
Because I keep finding references to uninitialised C arrays filled with
garbage if you don't initialise them.
Wait... hang on a second...
/fires up the ol' trusty gcc
[steve@ando c]$ cat array_init.c
#includestdio.h
int main()
{
int i;
int arr[10];
for (i = 0; i 10; i++) {
printf(arr[%d] = %d\n, i, arr[i]);
}
printf(\n);
return 0;
}
[steve@ando c]$ gcc array_init.c
[steve@ando c]$ ./a.out
arr[0] = -1082002360
arr[1] = 134513317
arr[2] = 2527220
arr[3] = 2519564
arr[4] = -1082002312
arr[5] = 134513753
arr[6] = 1294213
arr[7] = -1082002164
arr[8] = -1082002312
arr[9] = 2527220
What am I missing here?
What you're missing is that arr[] is an automatic variable. Put
a static in front of it, or move it outside the function (to become
global) and you'll see the difference.
--
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Re: Python Front-end to GCC
On Tue, 22 Oct 2013 08:04:21 -0700, Mark Janssen wrote: A language specification in BNF is just syntax. It doesn't say anything about semantics. So how could this be used to produce executable C code for a program? BNF is used to produce parsers. But a parser isn't sufficient. A C program is just syntax also. How does the compiler generate executable machine code? Extrapolate into a Python front-end to C. [Dave Angel responds:] Did you even read the paragraph you quoted above? The BNF specification does NOT completely describe a language, it only defines its syntax. [Steven D'Aprano responds:] Like every other language, C programs are certainly not *just* syntax. Here is some syntax: foo bar^ := Now, I don't know where y'all were taught Computer Science, Melbourne University Computer Science Department. How about you? but BNF specifies not only syntax (which would be the *tokens* of a language), but also its *grammar*; how syntax relates to linguistic categories like keywords, and tokens relate to each other. I'm not about to get into a debate about the difference between syntax and grammar as they apply to computer languages, because it doesn't matter. Neither syntax nor grammar tell you what something *means*, the semantics of the code. The parser knows that (say) x ^% y is legal and (say) x y ^% is not, but it doesn't know what machine code to generate when it sees x ^% y. That's not the job of the parser. I expect that some compilers -- ancient ones, or lousy ones, or simple ones -- have a single routine that do all the parsing, lexing, code generation, linking, optimizing, etc., rather than separate routines that do the parsing, the code generation, and so on. But even those compilers cannot just take a description of the syntax and intuit what it means. Syntax isn't enough. At some point, the compiler needs to know that ^ means to generate code to dereference pointers (like in Pascal), or perhaps it's bitwise or (like in C), or maybe even exponentiation (like in VisualBasic), or perhaps it's something completely different. Dave is claiming that BNF only defines the syntax of a language, but then Stephen goes on to supply some syntax that a BNF specification of the language would not allow (even though Steven calls it syntax which is what BNF in Dave's claim parses). I think you have misunderstood me. I gave an example of some invented syntax that your hypothetical language might choose to use. Here it is again: foo bar^ := Since I didn't provide the BNF specification for that syntax, you aren't in a position to say it is illegal. You should assume that it is legal syntax. If you really insist, I'll waste my time and yours and generate a BNF specification that allows that as valid syntax, or you could just accept that it's legal for this imaginary language. Your task is to describe what the code does, and hence what machine code your hypothetical compiler will generate, when it sees that line of code. You should be asking How the hell can I tell what that does? Exactly. That's the point. Neither can the compiler, not from syntax alone. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Tue, 22 Oct 2013 14:04:57 +, Dave Angel wrote: but here you go on to say the C code is unsafely skipping initialization, which is not the case. Are you talking generically, or specifically about the C code referenced in the link I gave? Memory is always zeroed is one of the advantages of Go over C and C++, at least according to Rob Pike: http://commandcenter.blogspot.com.au/2012/06/less-is-exponentially- more.html Go initializes variables to defined zero values, not simply to all-bits zero as (I think) C does. This isn't as great a feature as it seems, since the zero value for some built in types, e.g., map, is unusable without manual construction. In addition, you can't define a zero value for your own types. -- Neil Cerutti -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, 22 Oct 2013 16:53:07 +, Frank Miles wrote: [snip C code] What you're missing is that arr[] is an automatic variable. Put a static in front of it, or move it outside the function (to become global) and you'll see the difference. Ah, that makes sense. Thanks to everyone who corrected my misunderstanding. Well, actually, no it doesn't. I wonder why C specifies such behaviour? Why would you want non-global arrays to be filled with garbage? -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Mark Janssen dreamingforw...@gmail.com writes: I love it. Watch this... [context] A language specification in BNF is just syntax. It doesn't say anything about semantics. So how could this be used to produce executable C code for a program? BNF is used to produce parsers. But a parser isn't sufficient. A C program is just syntax also. How does the compiler generate executable machine code? Extrapolate into a Python front-end to C. [Dave Angel responds:] Did you even read the paragraph you quoted above? The BNF specification does NOT completely describe a language, it only defines its syntax. [Steven D'Aprano responds:] Like every other language, C programs are certainly not *just* syntax. Here is some syntax: foo bar^ := Now, I don't know where y'all were taught Computer Science, but BNF specifies not only syntax (which would be the *tokens* of a language), but also its *grammar*; how syntax relates to linguistic categories like keywords, and tokens relate to each other. Syntax is grammar. Tokens are part of the grammar (but often specified separately with a different grammar, usually regular expressions, which is a subset of BNF). So are you just confused or are you trollong? -- Piet van Oostrum p...@vanoostrum.org WWW: http://pietvanoostrum.com/ PGP key: [8DAE142BE17999C4] -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, 22 Oct 2013 23:20:52 +1100, Chris Angelico wrote: Considering that rapiding took about 1200ms (ish - again, cold cache) previously, adding even just 250ms is noticeable. Please excuse my skepticism, but in my experience, that would probably mean in practice: ... rapiding took about 1200ms, plus or minus 200ms, plus 500ms if the system is under load, plus 800ms if the developer vagued out for a moment, plus 1900ms if he happened to be scratching an itch, plus 2700ms if the anti-virus happened to be scanning something, plus 4100ms if the dev decided this was a good time to take a sip of coffee, plus 437000ms if he needed to make the coffee first, plus 7200ms if he was just taking a moment to check something on Reddit or answer an email... I don't have a lot of sympathy for this sort of micro-optimization of interactive software, where the random variation from run to run is often larger than the time being optimized, and where the human element is usually one or two orders of magnitude greater still. Yes, developers complain when they have to wait for the computer for half a second, or at least the one time in thirty that they *notice* that they're waiting. The other 29 times the computer is actually waiting for them. Still, I'm probably no better. Only instead of optimizing code, I tend to optimize travel time with short cuts that are guaranteed[1] to shave off a minute from a journey that takes thirty minutes, plus or minus six minutes. Show me a way to avoid waiting at traffic lights for 30s, and I'll take it, even if it means waiting for a break in the traffic at a Give Way sign for three minutes. So I shouldn't mock too much :-) You're right, of course, that 1/4 second is noticeable. I just find it hard to credit that it's *significant* in the circumstances you're describing. But I could be wrong. [1] Guarantee void in the presence of rain, fog, heavy winds, light winds, police radar traps, industrial action, civil protests, riots, wars, earthquakes, acts of God, or other cars. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, Oct 22, 2013 at 10:23 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Tue, 22 Oct 2013 16:53:07 +, Frank Miles wrote: [snip C code] What you're missing is that arr[] is an automatic variable. Put a static in front of it, or move it outside the function (to become global) and you'll see the difference. Ah, that makes sense. Thanks to everyone who corrected my misunderstanding. Well, actually, no it doesn't. I wonder why C specifies such behaviour? Why would you want non-global arrays to be filled with garbage? Its a performance benefit, for cases where you are going to fill the array from other means, such as from a file or other sources such as literals. The global and static variables are effectively free to zero due to standard OS behaviours. The issue is actually more general than arrays, as the same behavior exists for all the types in C. Stack and heap variables have undefined value when initialized, while global and static variables (which are really the same thing, but with differing lexical scopes) are zero-filled. -- Steven -- https://mail.python.org/mailman/listinfo/python-list -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Tue, 22 Oct 2013 16:53:07 +, Frank Miles wrote: [snip C code] What you're missing is that arr[] is an automatic variable. Put a static in front of it, or move it outside the function (to become global) and you'll see the difference. Ah, that makes sense. Thanks to everyone who corrected my misunderstanding. Well, actually, no it doesn't. I wonder why C specifies such behaviour? Why would you want non-global arrays to be filled with garbage? Fish(enc)ey. -- Neil Cerutti -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 18:23, Steven D'Aprano wrote: On Tue, 22 Oct 2013 16:53:07 +, Frank Miles wrote: [snip C code] What you're missing is that arr[] is an automatic variable. Put a static in front of it, or move it outside the function (to become global) and you'll see the difference. Ah, that makes sense. Thanks to everyone who corrected my misunderstanding. Well, actually, no it doesn't. I wonder why C specifies such behaviour? Why would you want non-global arrays to be filled with garbage? Static variables need be initialised only once, whereas auto variables exist on the stack, so they would need to be initialised repeatedly, which was considered too expensive, especially as they would be assigned to before use anyway (hopefully!). Of course, these days, with our much faster CPUs, we're not so bothered, and prefer to allocate on the heap. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Could you please be less snarky? We're trying to communicate here, and it is not at all clear yet who is confused and who is not. If you are interested in discussing technical topics, then discuss them. Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. -- MarkJ Tacoma, Washington -- https://mail.python.org/mailman/listinfo/python-list
using smtp in python
I'm trying to send an email using python. The mail content is taken from file and subject of the mail is name of the file. The program is invoked as ./mailclient.py -f from email address -d recipient email address -i file1 -s server IP address . How to i use server ip address and the mail id to send the email ? (would i require the password) -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tue, Oct 22, 2013 at 12:50 PM, Mark Janssen dreamingforw...@gmail.com wrote: Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Well, not quite. The lexer breaks the stream of characters up into tokens, which are fed to the parser, which produces an abstract syntax tree. From the WIkipedia entry: In computer science, an abstract syntax tree (AST), or just syntax tree, is a tree representation of the abstract syntactic structure of source code written in a programming language. Each node of the tree denotes a construct occurring in the source code. Skip -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Mark Janssen said: Unattributed No its not like those 'compilers' i dont really agree with a compiler generating C/C++ and saying its producing native code. I dont really believe its truely within the statement. Compilers that do that tend to put in alot of type saftey code and debugging internals at a high level to get things working in other projects i am not saying python compilers here i havent analysed enough to say this. Hmm, well what I'd personally find interesting from a computer science point of view is a app that will take a language specification in BNF (complete with keywords and all) and output C code which is then compiled to an executable as normal. This is how a front-end should be designed. A middle-layer for translating common language elements like lists, sets, etc, could make it easy. Taking this starting sortie I was going to try to justify what Mark is saying. Somewhat along the following lines. Things like lex and yacc (and equivalents in ecosystems other than C) give a kind of holy-grail in the following sense. When a writer of a lex/yacc spec does his thing, he does not need to think at the C level at all. Given that executable C is produced (and ignoring mishaps/bugs like shift-reduce conflicts etc) its a very ideal situation. The yacc-grammar (and its lex-helper) are completely declarative and yet they result in perfectly good ( O(n)) good C code. Taking this cue from the syntax domain one can treat it as a holy grail for semantics. ie can one specify the semantics of a language completely declaratively and have a lex/yacc *analogous* magic wand and get out a compiler/interpreter etc. Many people have pursued this holy grail but it remains elusive. Some examples: 1. Atribute grammars 2. Utrecht univs UUAG 3. Action semantics etc Note a key word above is analogous However when I see this: Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. all I will say is eyes-roll -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 18:50, Mark Janssen wrote: So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Could you please be less snarky? We're trying to communicate here, and it is not at all clear yet who is confused and who is not. If you are interested in discussing technical topics, then discuss them. Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. But you still need to specify the semantics. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Could you please be less snarky? Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. Hmm, I don't hear the boom yet. An Abstract Syntax Tree is a tree representation of a program. To use my previous example: the program 123 *!? 456 would become a tree: op: *!? num: 123 num: 456 There's still not enough information to compile this. Is your language Turing complete? -- MarkJ Tacoma, Washington -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Mark Janssen dreamingforw...@gmail.com wrote:
So which of you is confused? I ask that in the inclusive (not
exclusive OR) sense ;^) -- face says both.
Could you please be less snarky? We're trying to communicate here, and it
is not at all clear yet who is confused and who is not. If you are
interested in discussing technical topics, then discuss them.
Okay. The purpose of BNF (at least as I envision it) is to
produce/specify a *context-free* grammar.
Context-sensitive grammars can be parse, too.
A lexer parses the tokens specified in the BNF into an Abstract
Syntax Tree.
A lexer traditionaly reads the text and generates a stream of
tokens to the parser.
If one can produce such a tree for any given source, the
language, in theory, can be compiled by GCC into an executable.
What executable would GCC compile from a program that matched
this grammar?
spamgram = spam1, { ', ', more_spam }, '.'
spam1 = 'Spam'
more_spam = spam, { ', ', spam }
spam = 'spam'
--
Neil Cerutti
--
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Re: Python Front-end to GCC
Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. But you still need to specify the semantics. In my world, like writing pseudo-code or flow-charts, the AST *is* the semantics. What world are you guys from? -- MarkJ Tacoma, Washington -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Is your language Turing complete? 1) No, it's not. 2) So what? That should make it easier to compile to C, if anything. 3) Don't change the subject. Well, if your language is not Turing complete, it is not clear that you will be able to compile it at all. That's the difference between a calculator and a computer. Thank you. You may be seated. Mark J Tacoma, Washington -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 10/22/13 2:16 PM, Mark Janssen wrote: So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Could you please be less snarky? Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. Hmm, I don't hear the boom yet. An Abstract Syntax Tree is a tree representation of a program. To use my previous example: the program 123 *!? 456 would become a tree: op: *!? num: 123 num: 456 There's still not enough information to compile this. Is your language Turing complete? 1) No, it's not. 2) So what? That should make it easier to compile to C, if anything. 3) Don't change the subject. A BNF doesn't provide enough information to compile a program to C. That's all I'm trying to help you understand. If you don't agree, then we have to talk about the meaning of the words BNF, compile, program, and C. I applaud your interest in this topic. I think you need to learn more before you try to claim expertise, though. --Ned. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 10/22/13 2:22 PM, Mark Janssen wrote: Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. But you still need to specify the semantics. In my world, like writing pseudo-code or flow-charts, the AST *is* the semantics. What world are you guys from? Mark, you started this by describing a program that compiled to C. Now you say you are in the world of pseudo-code and flow-charts. Which is it? In the world where actual programs get compiled and run, you need to have semantics, and they aren't expressed in an AST or a BNF. I think you think that an AST is enough, but it isn't. I'm also not sure what you actually think because we don't stay on a topic long enough to get into the details that would shed light. It's fun to feel like you are right, and it's easy if you change the topic when the going gets tough. You've done this a number of times. I've tried to be polite, and I've tried to be helpful, but I'm sorry: either you don't understand a lot of the terms you are throwing around, or you aren't disciplined enough to focus on a topic long enough to explain yourself. Either way, I don't know how else to move the discussion forward. --Ned. -- https://mail.python.org/mailman/listinfo/python-list
Re: using smtp in python
On Tue, Oct 22, 2013 at 11:00 AM, ashikbe...@gmail.com wrote: I'm trying to send an email using python. The mail content is taken from file and subject of the mail is name of the file. The program is invoked as ./mailclient.py -f from email address -d recipient email address -i file1 -s server IP address . How to i use server ip address and the mail id to send the email ? (would i require the password) -- https://mail.python.org/mailman/listinfo/python-list Some SMTP servers require a password and some do not. I'm guessing more and more do, as spammers attack. Here's a module that shows how to do it with a password: http://stromberg.dnsalias.org/svn/mailer/trunk/mailer.py You can check it out with svn checkout url, or just browse to the URL in a web browser. HTH -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Tuesday, October 22, 2013 11:53:22 PM UTC+5:30, Ned Batchelder wrote: A BNF doesn't provide enough information to compile a program to C. That's all I'm trying to help you understand. If you don't agree, then we have to talk about the meaning of the words BNF, compile, program, and C. I believe we need to talk about the Dunning-Kruger effect -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 19:22, Mark Janssen wrote: Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. But you still need to specify the semantics. In my world, like writing pseudo-code or flow-charts, the AST *is* the semantics. What world are you guys from? The real world. :-) So what you're saying is that you generate an AST where there are certain pre-defined operations (primitives?) available? -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote:
On Tue, 22 Oct 2013 16:53:07 +, Frank Miles wrote:
[snip C code]
What you're missing is that arr[] is an automatic variable. Put a
static in front of it, or move it outside the function (to become
global) and you'll see the difference.
Ah, that makes sense. Thanks to everyone who corrected my
misunderstanding.
Well, actually, no it doesn't. I wonder why C specifies such behaviour?
Why would you want non-global arrays to be filled with garbage?
Firstly, it's not non-global arrays that have undefined contents.
It's _auto_ arrays that have undefined contents.
void foo(void)
{
int a[4]; // non-global, _auto_ variable and has undefined contents
}
void bar(void)
{
static int a[4]; // non-global, _static_ variable initially 0's
}
As to _why_ it's that way, you'd have to ask the guys who decided
that. I supect it's because zeroing static variables involves very
little run-time overhead, while zeroing auto variables could cause
huge amounts of overhead if that auto variable is declared inside the
innermost of nested loops. [Presumably a good optimizing compiler
would not zero an auto variable that was always set before it was
referenced, but it takes a lot of smarts for compiler to figure that
out correctly 100% of the time -- probably more smarts than a PDP-11
had room for.]
--
Grant Edwards grant.b.edwardsYow! Let's send the
at Russians defective
gmail.comlifestyle accessories!
--
https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 19:40, rusi wrote: On Tuesday, October 22, 2013 11:53:22 PM UTC+5:30, Ned Batchelder wrote: A BNF doesn't provide enough information to compile a program to C. That's all I'm trying to help you understand. If you don't agree, then we have to talk about the meaning of the words BNF, compile, program, and C. I believe we need to talk about the Dunning-Kruger effect No need for me to discuss that as I used to be big headed but now I'm perfect. -- Python is the second best programming language in the world. But the best has yet to be invented. Christian Tismer Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Neil Cerutti ne...@norwich.edu wrote: On 2013-10-22, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Tue, 22 Oct 2013 14:04:57 +, Dave Angel wrote: but here you go on to say the C code is unsafely skipping initialization, which is not the case. Are you talking generically, or specifically about the C code referenced in the link I gave? Memory is always zeroed is one of the advantages of Go over C and C++, at least according to Rob Pike: http://commandcenter.blogspot.com.au/2012/06/less-is-exponentially- more.html Go initializes variables to defined zero values, not simply to all-bits zero as (I think) C does. C initializes to defined zero values. For most machines in use today, those values _happen_ to be all-bits-zero. This makes the implementation trivial: chuck them all into some pre-defined section (e.g. .bss), and then on startup, you zero-out all the bits in the section without having to know what's where within that section. If you design a machine such that integer, pointer, and FP representations where 0, NULL, and 0.0 are all zero-bits, then life get's tougher for the guys writing the compiler and startup code. But the language doesn't require or assume that initializer values are all-bits-zero. FP values have to be initizliaed to 0.0. Int's have to be initialized to integer value 0, pointers have to be initialized to (void*)0. Nowhere it the languauge is it required or assumed that any or all of those values are all represented by contiguous blocks of all-zero-bits. This isn't as great a feature as it seems, since the zero value for some built in types, e.g., map, is unusable without manual construction. In addition, you can't define a zero value for your own types. -- Grant Edwards grant.b.edwardsYow! Oh my GOD -- the at SUN just fell into YANKEE gmail.comSTADIUM!! -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 10/22/13 1:50 PM, Mark Janssen wrote: So which of you is confused? I ask that in the inclusive (not exclusive OR) sense ;^) -- face says both. Could you please be less snarky? We're trying to communicate here, and it is not at all clear yet who is confused and who is not. If you are interested in discussing technical topics, then discuss them. Okay. The purpose of BNF (at least as I envision it) is to produce/specify a *context-free* grammar. A lexer parses the tokens specified in the BNF into an Abstract Syntax Tree. If one can produce such a tree for any given source, the language, in theory, can be compiled by GCC into an executable. Boom. Hmm, I don't hear the boom yet. An Abstract Syntax Tree is a tree representation of a program. To use my previous example: the program 123 *!? 456 would become a tree: op: *!? num: 123 num: 456 There's still not enough information to compile this. The operator *!? needs to have a meaning assigned to it. That's the role of the semantic specification of a language. That has to be provided somehow. A BNF, or a grammar, or a syntax, or an AST can't provide the semantics. That was the original point: syntax isn't enough. --Ned. -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Neil Cerutti ne...@norwich.edu writes: Context-sensitive grammars can be parse, too. That's not English. Do you mean parsed? But context-sentitive grammars cannot be specified by BNF. -- Piet van Oostrum p...@vanoostrum.org WWW: http://pietvanoostrum.com/ PGP key: [8DAE142BE17999C4] -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Piet van Oostrum p...@vanoostrum.org wrote: Neil Cerutti ne...@norwich.edu writes: Context-sensitive grammars can be parse, too. That's not English. Do you mean parsed? Thanks, yes, I meant parsed. But context-sentitive grammars cannot be specified by BNF. Yes. I thought Mark might have had a misconception that all programming languages have to be defined in BNF. -- Neil Cerutti -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 20:20, Piet van Oostrum wrote: Neil Cerutti ne...@norwich.edu writes: Context-sensitive grammars can be parse, too. That's not English. Do you mean parsed? But context-sentitive grammars cannot be specified by BNF. That's not English. Do you mean context-sensitive? :) -- Python is the second best programming language in the world. But the best has yet to be invented. Christian Tismer Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 22/10/2013 20:27, Neil Cerutti wrote: On 2013-10-22, Piet van Oostrum p...@vanoostrum.org wrote: Neil Cerutti ne...@norwich.edu writes: Context-sensitive grammars can be parse, too. That's not English. Do you mean parsed? Thanks, yes, I meant parsed. But context-sentitive grammars cannot be specified by BNF. Yes. I thought Mark might have had a misconception that all programming languages have to be defined in BNF. Please be kind enough to disambiguate Mark, as I would not wish to be tarred with the same brush. TIA. -- Python is the second best programming language in the world. But the best has yet to be invented. Christian Tismer Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
http://natigaals7ab.blogspot.com
http://natigaals7ab.blogspot.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Mark Lawrence breamore...@yahoo.co.uk wrote: On 22/10/2013 20:27, Neil Cerutti wrote: On 2013-10-22, Piet van Oostrum p...@vanoostrum.org wrote: Neil Cerutti ne...@norwich.edu writes: Context-sensitive grammars can be parse, too. That's not English. Do you mean parsed? Thanks, yes, I meant parsed. But context-sentitive grammars cannot be specified by BNF. Yes. I thought Mark might have had a misconception that all programming languages have to be defined in BNF. Please be kind enough to disambiguate Mark, as I would not wish to be tarred with the same brush. Oops! I didn't notice he'd dropped out of the attributions. I was speculating about Mark Janssen, not you. -- Neil Cerutti -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
Anyone there to help me out??? -- https://mail.python.org/mailman/listinfo/python-list
numpy masked_where
Why does the numpy masked_where create a special case for all False? import numpy x = numpy.array([[9,9,9,9,9,9],[9,9,9,9,9,9],[9,9,9,9,9,9],[9,9,9,9,9,9]]) y = numpy.ma.masked_where(x3,x) y.mask Out[1]: False z= numpy.arange(20) z.reshape(4,5) Out[1]: array([[ 0, 1, 2, 3, 4], [ 5, 6, 7, 8, 9], [10, 11, 12, 13, 14], [15, 16, 17, 18, 19]]) y = numpy.ma.masked_where(z3,z) y.mask Out[1]: array([ True, True, True, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], dtype=bool) Is there a good way to work around this and get an all False array? Thanks -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Grant Edwards invalid@invalid.invalid wrote: C initializes to defined zero values. For most machines in use today, those values _happen_ to be all-bits-zero. This makes the implementation trivial: chuck them all into some pre-defined section (e.g. .bss), and then on startup, you zero-out all the bits in the section without having to know what's where within that section. If you design a machine such that integer, pointer, and FP representations where 0, NULL, and 0.0 are all zero-bits, then life ^ not get's tougher for the guys writing the compiler and startup code. -- Grant Edwards grant.b.edwardsYow! We are now enjoying at total mutual interaction in gmail.coman imaginary hot tub ... -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
On 22/10/2013 21:15, Pratik Mehta wrote: Anyone there to help me out??? There are plenty of people who will help you out, but if and only if you make an attempt at writing some code and then ask for assistance when you run into problems. -- Python is the second best programming language in the world. But the best has yet to be invented. Christian Tismer Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
Tkinter tutorial?
I have some experience with Python, having used it for a couple of years. Until now, my builder of choice for cross-platform GUI applications has been wxPython (with wxGlade), and I have been well satisfied with these tools. However, for a different project I need to get up to a reasonable speed with tkinter. Could some kind soul recommend a suitable on-line tutorial, or a (free) ebook? Thanks. -- https://mail.python.org/mailman/listinfo/python-list
Re: Animated PNG Vs Gif: 120fr 3D Python Powered Logo
On Tue, Oct 22, 2013 at 8:23 AM, Metallicow metaliobovi...@gmail.com wrote: Maybe there is an option with the browsers to disable gif 0 delay mangling...? Perhaps there is, but you couldn't rely on the user to have changed it. So What did you use to increase the speed of the gif? ...Errm Program or whatever used to mod it? I made the gif with gimp, since I find importing/exporting as layers a bit easier than using imageready. I used a freeware called Photoscape to open the gif, change the delays, and resave it. -- https://mail.python.org/mailman/listinfo/python-list
Re: Tkinter tutorial?
On 22/10/2013 21:57, Walter Hurry wrote: I have some experience with Python, having used it for a couple of years. Until now, my builder of choice for cross-platform GUI applications has been wxPython (with wxGlade), and I have been well satisfied with these tools. However, for a different project I need to get up to a reasonable speed with tkinter. Could some kind soul recommend a suitable on-line tutorial, or a (free) ebook? Thanks. Ask Google! :-) In practice I've had to go looking for specific answers, but there's info available from various places, such as: http://effbot.org/tkinterbook/ -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Wed, Oct 23, 2013 at 4:27 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Tue, 22 Oct 2013 23:20:52 +1100, Chris Angelico wrote: Considering that rapiding took about 1200ms (ish - again, cold cache) previously, adding even just 250ms is noticeable. Please excuse my skepticism, but in my experience, that would probably mean in practice: ... rapiding took about 1200ms, plus or minus 200ms, plus 500ms if the system is under load, plus 800ms if the developer vagued out for a moment, plus 1900ms if he happened to be scratching an itch, plus 2700ms if the anti-virus happened to be scanning something, plus 4100ms if the dev decided this was a good time to take a sip of coffee, plus 437000ms if he needed to make the coffee first, plus 7200ms if he was just taking a moment to check something on Reddit or answer an email... Yes; and more importantly, at the times when it actually would be used, the cache will likely be warm. You're right, of course, that 1/4 second is noticeable. I just find it hard to credit that it's *significant* in the circumstances you're describing. But I could be wrong. Yeah, but the problem here is a fundamental of human nature. I mentioned earlier that I was trying to sell the notion of an instant pre-check of the code. I use one myself, have done for ages, and it's helped me often enough that I don't care if it occasionally adds a second to my time. (I have a few such assistants that involve searching through recent git commit messages, so they can take multiple seconds if the cache is cold. I don't care; once it's in cache, it's way faster.) But imagine sitting beside a skeptical fellow developer and saying, Enable this line here and it'll catch these sorts of bugs before you even spin it up in your testbox - and he hits F7 and notices that it takes twice as long as he's used to. That's going to make it a pretty hard sell. That's why I wanted to get the time cost of the smoke test as low as I possibly could, even on a cold cache. (I'm used to tough sells at my workplace. It took years before we adopted source control yes, seriously. And even once we did, I had to fight to get other developers to make useful commits and commit messages. One in particular - who, fortunately, is no longer with us - saw the whole thing as a nuisance that got in the way of his genius, so he'd just commit once at the end of the day with a barely-useful message. But then, he was pretty astounding in a lot of other areas, too - really amazing... like using the For-Case paradigm in PHP with an off-by-one error...) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
In 03db6a3f-3b1c-4516-8bee-4e3a362eb...@googlegroups.com Pratik Mehta pratik.mehta13...@gmail.com writes: Anyone there to help me out??? Command-Shift-3 takes a screenshot of the whole screen and saves it as a file on the desktop. Command-Control-Shift-3: takes a screenshot of the whole screen and saves it to the clipboard. For other options (such as taking a screenshot of a window or a specific region on the screen), see http://guides.macrumors.com/Taking_Screenshots_in_Mac_OS_X I wonder what this has to do with Python though. -- John Gordon Imagine what it must be like for a real medical doctor to gor...@panix.comwatch 'House', or a real serial killer to watch 'Dexter'. -- https://mail.python.org/mailman/listinfo/python-list
functools and objective usage
Dear all, Suppose i have function name, 3 arguments for it, and object of its caller such as self.blahbalah So: my function is: self.blahblah.name(arg1,arg2,arg3) I read functools documentations, may be objictive usage and functionality differ, Do you have experience with objective usage ? http://docs.python.org/2/library/functools.html#partial-objects I need to use it in my class, Thank you, Yours, Mohsen -- https://mail.python.org/mailman/listinfo/python-list
Re: using smtp in python
On Tuesday 2013 October 22 11:44, Dan Stromberg wrote: Some SMTP servers require a password and some do not POP3 before SMTP ? -- Yonder nor sorghum stenches shut ladle gulls stopper torque wet strainers. -- https://mail.python.org/mailman/listinfo/python-list
Re: Tkinter tutorial?
Walter Hurry walterhu...@lavabit.com writes: However, for a different project I need to get up to a reasonable speed with tkinter. Could some kind soul recommend a suitable on-line tutorial, or a (free) ebook? TkDocs URL:http://www.tkdocs.com/ is both a book for purchase (“Modern Tkinter”) and a cross-language tutorial for Tk, taking full advantage of modern features of Tk 8.5 and 8.6. The example code attempts to hew quite closely to the original Tcl, so it makes for rather awful Python. But you do learn how Tkinter works. -- \“If you continue running Windows, your system may become | `\unstable.” —Microsoft, Windows 95 bluescreen error message | _o__) | Ben Finney -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
On 10/22/13 4:15 PM, Pratik Mehta wrote:
Anyone there to help me out???
import os
os.system('screencapture', 'foo.png')
--
Kevin Walzer
Code by Kevin/Mobile Code by Kevin
http://www.codebykevin.com
http://www.wtmobilesoftware.com
--
https://mail.python.org/mailman/listinfo/python-list
Re: functools and objective usage
Mohsen Pahlevanzadeh moh...@pahlevanzadeh.org writes: Suppose i have function name, 3 arguments for it, and object of its caller such as self.blahbalah This doesn't make much sense to me. I think you mean: You have an object, ‘self.blahblah’, which has a function attribute, ‘name’. (Aside: Please choose better example names, these make it rather difficult to talk about.) So: my function is: self.blahblah.name(arg1,arg2,arg3) Your *function* is ‘self.blahblah.name’. One possible way to express a *call* that function is ‘self.blahblah.name(arg1, arg2, arg3)’. I read functools documentations, may be objictive usage and functionality differ, Do you have experience with objective usage ? http://docs.python.org/2/library/functools.html#partial-objects I don't understand what the question is. You have shown a way to call your function; what do you want to do now? I need to use it in my class, Feel free :-) -- \ “Pinky, are you pondering what I'm pondering?” “I think so, | `\Brain, but I find scratching just makes it worse.” —_Pinky and | _o__) The Brain_ | Ben Finney -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
Mark Janssen dreamingforw...@gmail.com writes: Is your language Turing complete? 1) No, it's not. 2) So what? That should make it easier to compile to C, if anything. 3) Don't change the subject. Well, if your language is not Turing complete, it is not clear that you will be able to compile it at all. That's the difference between a calculator and a computer. You think a language that is not Turing-complete cannot be compiled? What nonsense is that. Please Mark, spare us your nonsense. -- Piet van Oostrum p...@vanoostrum.org WWW: http://pietvanoostrum.com/ PGP key: [8DAE142BE17999C4] -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
On 10/22/13 6:08 PM, Kevin Walzer wrote:
On 10/22/13 4:15 PM, Pratik Mehta wrote:
Anyone there to help me out???
import os
os.system('screencapture', 'foo.png')
...and see 'man screencapture' for options.
I leave setting up a Tkinter GUI with proper key bindings as an exercise
for the reader.
--
Kevin Walzer
Code by Kevin/Mobile Code by Kevin
http://www.codebykevin.com
http://www.wtmobilesoftware.com
--
https://mail.python.org/mailman/listinfo/python-list
Re: Tkinter tutorial?
On 10/22/2013 03:06 PM, Ben Finney wrote: Walter Hurry walterhu...@lavabit.com writes: However, for a different project I need to get up to a reasonable speed with tkinter. Could some kind soul recommend a suitable on-line tutorial, or a (free) ebook? TkDocs URL:http://www.tkdocs.com/ is both a book for purchase (“Modern Tkinter”) and a cross-language tutorial for Tk, taking full advantage of modern features of Tk 8.5 and 8.6. The example code attempts to hew quite closely to the original Tcl, so it makes for rather awful Python. But you do learn how Tkinter works. Awesome! Just bought my copy. :D -- ~Ethan~ -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 2013-10-22, Mark Janssen dreamingforw...@gmail.com wrote: Is your language Turing complete? 1) No, it's not. 2) So what? That should make it easier to compile to C, if anything. 3) Don't change the subject. Well, if your language is not Turing complete, it is not clear that you will be able to compile it at all. Whether a language is turing complete or not has _NOTHING_ to do with whether it can be compiled or not. That's the difference between a calculator and a computer. No, it isn't. Thank you. You may be seated. Dunno what you're smoking, but you sure are getting your money's worth... -- Grant -- https://mail.python.org/mailman/listinfo/python-list
Re: functools and objective usage
On 22/10/2013 23:13, Ben Finney wrote: Mohsen Pahlevanzadeh moh...@pahlevanzadeh.org writes: Suppose i have function name, 3 arguments for it, and object of its caller such as self.blahbalah This doesn't make much sense to me. I think you mean: You have an object, ‘self.blahblah’, which has a function attribute, ‘name’. Perhaps the OP means that 'name' is a variable which is bound to the name of the function/method, which is an attribute of self.blahbalah. (Aside: Please choose better example names, these make it rather difficult to talk about.) So: my function is: self.blahblah.name(arg1,arg2,arg3) Your *function* is ‘self.blahblah.name’. One possible way to express a *call* that function is ‘self.blahblah.name(arg1, arg2, arg3)’. If 'name' is bound to the name, then: func = getattr(self.blahblah, name) func(arg1, arg2, arg3) or just: getattr(self.blahblah, name)(arg1, arg2, arg3) I read functools documentations, may be objictive usage and functionality differ, Do you have experience with objective usage ? http://docs.python.org/2/library/functools.html#partial-objects I don't understand what the question is. You have shown a way to call your function; what do you want to do now? I need to use it in my class, Feel free :-) -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
Hey John, I want to code my own Snapshot taking program using Python. Hence, had posted this question... -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
Hey Kevin, Thanks for reverting. I know about the screencapture function and the parameters available. But, how would I take the user input, as in, that is just command-line, as soon as I execute the program, it will take whatever kind of parameter is passed under screencapture. I want that, in the same program, if the user presses Shift+Command+3, whole screenshot should be taken. When, Shift + Command + 4 is pressed, a particular frame should be displayed to select the area / region. Also, I want to create my own command : Shift + Command + 5 == this is specially for web browser, whenever I press this key on any of the web-page, the whole web page should be grabbed along with its snapshot, and snapshot's filename should be web-page's url which I am currently on. Also, this process should be executing at the backend, so that, whenever these keys are pressed, it overrides the system's functionality and uses mine. -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
Hey Mark, Thanks for reverting. I had tried coding it using os.system(screencapture -s /filepath) // for selecting a particular region.. I have replied to Kevin's comment, that's exactly what I am looking for. :) Thanks ... -- https://mail.python.org/mailman/listinfo/python-list
Re: Screenshots in Mac OS X
On 10/22/13 8:19 PM, Pratik Mehta wrote: Hey Kevin, Thanks for reverting. I know about the screencapture function and the parameters available. But, how would I take the user input, as in, that is just command-line, as soon as I execute the program, it will take whatever kind of parameter is passed under screencapture. I want that, in the same program, if the user presses Shift+Command+3, whole screenshot should be taken. When, Shift + Command + 4 is pressed, a particular frame should be displayed to select the area / region. Also, I want to create my own command : Shift + Command + 5 == this is specially for web browser, whenever I press this key on any of the web-page, the whole web page should be grabbed along with its snapshot, and snapshot's filename should be web-page's url which I am currently on. Also, this process should be executing at the backend, so that, whenever these keys are pressed, it overrides the system's functionality and uses mine. There are no simple answers to these questions. With Tkinter, it's possible to code a basic UI and bind combinations of specific keys to trigger specific callbacks, which can fire specific sequences of arguments to the screencapture CLI tool. That's the quick and dirty way. I'm not going to write this code for you. Look at TkDocs.com and effbot's site for an introduction to Tkinter. If you are not looking for a GUI app to do this, but some sort of system-level daemon, that requires a lower level of coding. You'll need to look at such system frameworks as CoreGraphics and Cocoa to find the API's you need. PyObjC (Python binding to Cocoa) can probably be helpful here. Frankly, I'm not sure Python is the best tool here, but if you go this route, you want a Python API that hews as closely to the system-level calls as possible, and PyObjC will likely be your best path here. --Kevin -- Kevin Walzer Code by Kevin/Mobile Code by Kevin http://www.codebykevin.com http://www.wtmobilesoftware.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Using with context handler, and catching specific exception?
Hi,
I'm actually on Python 2.7, so we don't have access to any of those nice new
exceptions in Python 3.3 =(:
http://docs.python.org/2.7/library/exceptions.html#exception-hierarchy
@Ben - Good point about just catching the more general exception, and just
printing out the string message.
I suppose in most cases, we won't be doing anything special for the different
types (e.g. file not found, permission error, is a directory etc.) - it'll just
be going into logs.
Is there anything wrong with me just catching Exception in this case of
opening a file, and printing the message from there?
Cheers,
Victor
On Tuesday, 22 October 2013 14:53:58 UTC+11, Ben Finney wrote:
Victor Hooi victorh...@gmail.com writes:
Aha, good point about IOError encapsulating other things, I'll use
FileNotFoundError, and also add in some other except blocks for the
other ones.
Or not; you can catch OSError, which is the parent of FileNotFoundError
URL:http://docs.python.org/3/library/exceptions.html#exception-hierarchy,
but don't assume in your code that it means anything more specific.
You should only catch specific exceptions if you're going to do
something specific with them. If all you want to do is log them and move
on, then catch a more general class and ask the exception object to
describe itself (by using it in a string context).
In versions of Python before 3.3, you have to catch EnvironmentError
URL:http://docs.python.org/3.2/library/exceptions.html#EnvironmentError
and then distinguish the specific errors by their ‘errno’ attribute
URL:http://docs.python.org/3.2/library/errno.html::
import errno
try:
with open('somefile.log', 'wb') as f:
f.write(hello there)
except EnvironmentError as exc:
if exc.errno == errno.ENOENT:
handle_file_not_found_error()
elif exc.errno == errno.EACCES:
handle_permission_denied()
elif exc.errno == errno.EEXIST:
handle_file_exists()
…
else:
handle_all_other_environment_errors()
That's much more clumsy, which is why it was improved in the latest
Python. If you can, code for Python 3.3 or higher.
--
\ “Unix is an operating system, OS/2 is half an operating system, |
`\Windows is a shell, and DOS is a boot partition virus.” —Peter |
_o__)H. Coffin |
Ben Finney
--
https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 23/10/2013 4:40 AM, Ned Batchelder wrote: I've tried to be polite, and I've tried to be helpful, but I'm sorry: either you don't understand a lot of the terms you are throwing around, or you aren't disciplined enough to focus on a topic long enough to explain yourself. Either way, I don't know how else to move the discussion forward. You forgot to end with a well-warranted Boom. Mark Janssen is rapidly becoming Xah Lee 2.0, identical down to the repugnant misogyny he expresses elsewhere. The only difference is one of verbosity. -- https://mail.python.org/mailman/listinfo/python-list
Re: pip won't ignore system-installed files
if you use a newer version of pip i think this should work. On Tuesday, October 22, 2013 9:11:40 AM UTC-4, Neal Becker wrote: IIUC, it is perfectly legitimate to do install into --user to override system- wide installed modules. Thus, I should be able to do: pip install --user --up blah even though there is already a package blah in /usr/lib/pythonxxx/site_packages/... But even with -I (ignore installed) switch, pip fails: pip install --user --up -I matplotlib ... Installing collected packages: matplotlib, numpy, python-dateutil, tornado, pyparsing, nose, six Found existing installation: matplotlib 1.2.0 Uninstalling matplotlib: Exception: Traceback (most recent call last): File /usr/lib/python2.7/site-packages/pip-1.2.1- py2.7.egg/pip/basecommand.py, line 107, in main status = self.run(options, args) File /usr/lib/python2.7/site-packages/pip-1.2.1- py2.7.egg/pip/commands/install.py, line 261, in run requirement_set.install(install_options, global_options) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/req.py, line 1162, in install requirement.uninstall(auto_confirm=True) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/req.py, line 495, in uninstall paths_to_remove.remove(auto_confirm) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/req.py, line 1492, in remove renames(path, new_path) File /usr/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/util.py, line 273, in renames shutil.move(old, new) File /usr/lib64/python2.7/shutil.py, line 302, in move os.unlink(src) OSError: [Errno 13] Permission denied: '/usr/lib64/python2.7/site- packages/matplotlib-1.2.0-py2.7.egg-info' Can we please fix this? -- https://mail.python.org/mailman/listinfo/python-list
Re: functools and objective usage
Mohsen Pahlevanzadeh moh...@pahlevanzadeh.org writes: Dear all, Suppose i have function name, 3 arguments for it, and object of its caller such as self.blahbalah So: my function is: self.blahblah.name(arg1,arg2,arg3) I read functools documentations, may be objictive usage and functionality differ, Do you have experience with objective usage ? http://docs.python.org/2/library/functools.html#partial-objects What do you mean with objective usage? -- Piet van Oostrum p...@vanoostrum.org WWW: http://pietvanoostrum.com/ PGP key: [8DAE142BE17999C4] -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On Wednesday, October 23, 2013 7:06:40 AM UTC+5:30, alex23 wrote: On 23/10/2013 4:40 AM, Ned Batchelder wrote: I've tried to be polite, and I've tried to be helpful, but I'm sorry: either you don't understand a lot of the terms you are throwing around, or you aren't disciplined enough to focus on a topic long enough to explain yourself. Either way, I don't know how else to move the discussion forward. You forgot to end with a well-warranted Boom. Mark Janssen is rapidly becoming Xah Lee 2.0, identical down to the repugnant misogyny he expresses elsewhere. The only difference is one of verbosity. Hey! Time to stop punching up a guy -- even (because?) he's a nut -- rather a hard one tho -- https://mail.python.org/mailman/listinfo/python-list
Re: Python Front-end to GCC
On 10/22/2013 12:28 PM, Mark Janssen wrote: Thank you. You may be seated. Ranting Rick, is that you? -- https://mail.python.org/mailman/listinfo/python-list
