Re: How to use while within the command in -c option of python?
On 13 October 2012 17:38, Joshua Landau joshua.landau...@gmail.com wrote: This here isn't a flaw in Python, though. It's a flaw in the command-line interpreter. By putting it all on one line, you are effectively saying: group these. Which is the same as an if True: block, and some things like Reinteract even supply a grouping block like build. That said, because some shells suck it would be nice if: python -c a=1\nif a:print(a) worked (just for -c). And, spurred on by another thread, this has become possible. Make a file like so, install it if you wish. import sys evaluable = sys.argv[1].encode(utf8).decode(unicode_escape) exec(evaluable) This lets you do this: python unicode_escape.py a = []##\nfor x in range(100):##\n a.append(x)##\n a.append(x**2)##\nprint(a) It's ugly, but it works and only takes one line. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On Sat, Oct 13, 2012 at 12:32:41AM +, Steven D'Aprano wrote: He gets SyntaxError because you can't follow a semicolon with a statement that begins a block. Can someone provide a link on where to find this type of information? I was just hunting through “The Python Language Reference” and could not find anything explicit. The only thing I found is http://docs.python.org/reference/simple_stmts.html “Several simple statements may occur on a single line separated by semicolons.” Anyways, this does not explicitly say “You shall not put a compound statement after a simple statement separated by a semicolon.”, right? Regards, Thomas Bach. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On Sat, Oct 13, 2012 at 7:41 PM, Thomas Bach thb...@students.uni-mainz.de wrote: On Sat, Oct 13, 2012 at 12:32:41AM +, Steven D'Aprano wrote: He gets SyntaxError because you can't follow a semicolon with a statement that begins a block. Can someone provide a link on where to find this type of information? I was just hunting through “The Python Language Reference” and could not find anything explicit. The only thing I found is http://docs.python.org/reference/simple_stmts.html “Several simple statements may occur on a single line separated by semicolons.” Anyways, this does not explicitly say “You shall not put a compound statement after a simple statement separated by a semicolon.”, right? It's more that Python treats simple and compound statements as completely separate beasts. You can combine simple statements on one line, but compound statements mustn't be. In my opinion, this is a major wart in Python syntax. You can argue all you like about how it reduces code clarity to put these sorts of things together, but that's a job for a style guide, NOT a language requirement. Most code won't put an assignment followed by an if/while/for, but when I'm working interactively, I often want to recall an entire statement to edit and reuse, complete with its initialization - something like (contrived example): a=collections.defaultdict(int) for x in open(RilvierRex.txt): a[x]+=1 Then I keep doing stuff, keep doing stuff, and then come back to this pair of lines. Since they're two lines, I have to recall them as two separate entities, rather than as an initializer and the code that uses it. Logically, they go together. Logically, they're on par with a list comprehension, which initializes, loops, and assigns, all as a single statement. But syntactically, they're two statements that have to go on separate lines. To force that sort of thing to be a single recallable statement, I can do stupid tricks like: if True: a=collections.defaultdict(int) for x in open(RilvierRex.txt): a[x]+=1 but that only works in IDLE, not in command-line interactive Python. Note, by the way, that it's fine to put the statement _inside_ the for on the same line. It's even legal to have multiple such statements: for x in (1,2,3): print(x); print(x); 1 1 2 2 3 3 If there's any ambiguity, it would surely be that, and not the simple statement being first. Okay, rant over. I'll go back to being nice now. :) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On 13 October 2012 10:03, Chris Angelico ros...@gmail.com wrote: On Sat, Oct 13, 2012 at 7:41 PM, Thomas Bach thb...@students.uni-mainz.de wrote: On Sat, Oct 13, 2012 at 12:32:41AM +, Steven D'Aprano wrote: He gets SyntaxError because you can't follow a semicolon with a statement that begins a block. Can someone provide a link on where to find this type of information? I was just hunting through “The Python Language Reference” and could not find anything explicit. The only thing I found is http://docs.python.org/reference/simple_stmts.html “Several simple statements may occur on a single line separated by semicolons.” Anyways, this does not explicitly say “You shall not put a compound statement after a simple statement separated by a semicolon.”, right? It's more that Python treats simple and compound statements as completely separate beasts. You can combine simple statements on one line, but compound statements mustn't be. In my opinion, this is a major wart in Python syntax. You can argue all you like about how it reduces code clarity to put these sorts of things together, but that's a job for a style guide, NOT a language requirement. Most code won't put an assignment followed by an if/while/for, but when I'm working interactively, I often want to recall an entire statement to edit and reuse, complete with its initialization - something like (contrived example): a=collections.defaultdict(int) for x in open(RilvierRex.txt): a[x]+=1 Then I keep doing stuff, keep doing stuff, and then come back to this pair of lines. Since they're two lines, I have to recall them as two separate entities, rather than as an initializer and the code that uses it. Logically, they go together. Logically, they're on par with a list comprehension, which initializes, loops, and assigns, all as a single statement. But syntactically, they're two statements that have to go on separate lines. To force that sort of thing to be a single recallable statement, I can do stupid tricks like: if True: a=collections.defaultdict(int) for x in open(RilvierRex.txt): a[x]+=1 but that only works in IDLE, not in command-line interactive Python. Note, by the way, that it's fine to put the statement _inside_ the for on the same line. It's even legal to have multiple such statements: for x in (1,2,3): print(x); print(x); 1 1 2 2 3 3 If there's any ambiguity, it would surely be that, and not the simple statement being first. Okay, rant over. I'll go back to being nice now. :) This here isn't a flaw in Python, though. It's a flaw in the command-line interpreter. By putting it all on one line, you are effectively saying: group these. Which is the same as an if True: block, and some things like Reinteract even supply a grouping block like build. That said, because some shells suck it would be nice if: python -c a=1\nif a:print(a) worked (just for -c). -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On Sun, Oct 14, 2012 at 3:38 AM, Joshua Landau
joshua.landau...@gmail.com wrote:
This here isn't a flaw in Python, though. It's a flaw in the command-line
interpreter. By putting it all on one line, you are effectively saying:
group these. Which is the same as an if True: block, and some things
like Reinteract even supply a grouping block like build.
That said, because some shells suck it would be nice if:
python -c a=1\nif a:print(a)
worked (just for -c).
Yes, that'd be nice. But it still leaves the big question of why
Python requires \n to separate one statement from another. It IS a
flaw in Python that it requires one specific statement separator in
this instance, even though it'll accept two in another instance.
Here's a side challenge. In any shell you like, start with this
failing statement, and then fix it without retyping anything:
sikorsky@sikorsky:~$ python -c a=1; if a: print(a)
File string, line 1
a=1; if a: print(a)
^
SyntaxError: invalid syntax
In bash, I was unable to insert a newline into the quoted string. My
only option was to backspace everything after the point where I wanted
the newline, then hit enter, then retype the if. I'm curious to know
if that's simply because I didn't think of (some bash feature), or
alternatively, if there's another shell that would have made this
easy.
Back to the main point. In C-like languages, the newline is nothing
special. (ECMAScript allows the omission of semicolons at end of line
in many cases, but many style guides recommend using them anyway.) You
can, if you so desire, put all your code into a single line. It's then
up to the project's style guide to decide how things should be laid
out. For instance, this is multiple statements in PHP, but I see it as
one logical action:
$bar=array(); for ($foo as $k=$v) $bar[$k]=p.$v./p;
It's one statement in Python:
bar = [p+x+/p for x in foo]
It's one statement in Pike:
array bar = map(foo,lambda(string x) {return p+x+/p;});
So it should be allowed to be put on one line. And in languages whose
syntax derives from C, you almost certainly can. (I can't think of any
counter-examples, though that certainly doesn't prove they don't
exist.) But the same thing is forced onto two lines in Python, and not
for syntactic reasons - at least, not that I can see. Perhaps someone
can enlighten me.
Is there any fundamental reason that the syntax couldn't be expanded
to permit statement; statement for any two given statements?
ChrisA
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Re: How to use while within the command in -c option of python?
Chris Angelico writes: Here's a side challenge. In any shell you like, start with this failing statement, and then fix it without retyping anything: sikorsky@sikorsky:~$ python -c a=1; if a: print(a) File string, line 1 a=1; if a: print(a) ^ SyntaxError: invalid syntax In bash, I was unable to insert a newline into the quoted string. My only option was to backspace everything after the point where I wanted the newline, then hit enter, then retype the if. I'm curious to know if that's simply because I didn't think of (some bash feature), or alternatively, if there's another shell that would have made this easy. C-v C-j inserts a newline for me, in bash. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On Sun, Oct 14, 2012 at 4:43 AM, Jussi Piitulainen jpiit...@ling.helsinki.fi wrote: Chris Angelico writes: Here's a side challenge. In any shell you like, start with this failing statement, and then fix it without retyping anything: sikorsky@sikorsky:~$ python -c a=1; if a: print(a) C-v C-j inserts a newline for me, in bash. Ah! So it does. Thanks. *stashes that away in the handy commands index in his brain* ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On 13 October 2012 18:23, Chris Angelico ros...@gmail.com wrote:
On Sun, Oct 14, 2012 at 3:38 AM, Joshua Landau
joshua.landau...@gmail.com wrote:
This here isn't a flaw in Python, though. It's a flaw in the command-line
interpreter. By putting it all on one line, you are effectively saying:
group these. Which is the same as an if True: block, and some things
like Reinteract even supply a grouping block like build.
That said, because some shells suck it would be nice if:
python -c a=1\nif a:print(a)
worked (just for -c).
Yes, that'd be nice. But it still leaves the big question of why
Python requires \n to separate one statement from another. It IS a
flaw in Python that it requires one specific statement separator in
this instance, even though it'll accept two in another instance.
Not really. The two things are fundamentally different. Yes, it's hard to
think of another example, but they aren't the same. ; means implicit
newline to the *same indentation*, whereas a newline does not.
Here's a side challenge. In any shell you like, start with this
failing statement, and then fix it without retyping anything:
sikorsky@sikorsky:~$ python -c a=1; if a: print(a)
File string, line 1
a=1; if a: print(a)
^
SyntaxError: invalid syntax
In bash, I was unable to insert a newline into the quoted string. My
only option was to backspace everything after the point where I wanted
the newline, then hit enter, then retype the if. I'm curious to know
if that's simply because I didn't think of (some bash feature), or
alternatively, if there's another shell that would have made this
easy.
I have to thank Jussi Piitulainen for the command here, I'm likely gonna'
use that quite a bit.
Back to the main point. In C-like languages, the newline is nothing
special. (ECMAScript allows the omission of semicolons at end of line
in many cases, but many style guides recommend using them anyway.) You
can, if you so desire, put all your code into a single line. It's then
up to the project's style guide to decide how things should be laid
out. For instance, this is multiple statements in PHP, but I see it as
one logical action:
$bar=array(); for ($foo as $k=$v) $bar[$k]=p.$v./p;
It's one statement in Python:
bar = [p+x+/p for x in foo]
It's one statement in Pike:
array bar = map(foo,lambda(string x) {return p+x+/p;});
So it should be allowed to be put on one line
Your argument goes:
FACT 1: You can do this in one statement, in one line.
FACT 2: In other languages you can do this in two statements, in one line
CONCULSION: You should be able to do this in two statements, in one line
Which I don't agree with. I understand that it is one *logical action*, but
so is multiplying a matrix. We have functions to *wrap* logical actions
that are composed of multiple logical actions.
The problem is that Python uses indentation. That's fundamentally the
problem.
And in languages whose
syntax derives from C, you almost certainly can. (I can't think of any
counter-examples, though that certainly doesn't prove they don't
exist.) But the same thing is forced onto two lines in Python, and not
for syntactic reasons - at least, not that I can see. Perhaps someone
can enlighten me.
Is there any fundamental reason that the syntax couldn't be expanded
to permit statement; statement for any two given statements?
Because Python uses indentation, what would if A: print(1); if B:
print(2) even do? It *has* to fail, because we have to assume consistent
indentation for ;s*. With \n as I proposed, you still have to indent:
it is just a method to bypass lame shells [it would become if A:
print(1)\nif B: print(2)].
Blocks that avoid this have been done to death with multi-line lambdas, and
the majority of people don't like them. I'm sway-able, but it's not going
to happen because Guido and most of the peeps with power aren't. Anything
that challenges the standard now is dead from the start.
* You *could* have some rules that govern ambiguities well, but none that I
can think of would be *both* backward-compatible *and* complete. If it's
incomplete we've just moved the goalpost.
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Re: How to use while within the command in -c option of python?
On Sun, Oct 14, 2012 at 5:21 AM, Joshua Landau joshua.landau...@gmail.com wrote: Because Python uses indentation, what would if A: print(1); if B: print(2) even do? It has to fail, because we have to assume consistent indentation for ;s*. With \n as I proposed, you still have to indent: it is just a method to bypass lame shells [it would become if A: print(1)\nif B: print(2)]. sikorsky@sikorsky:~/cpython$ python -c if False: print(1); print(2) sikorsky@sikorsky:~/cpython$ python -c if True: print(1); print(2) 1 2 sikorsky@sikorsky:~/cpython$ The semicolon separates statements, but doesn't change nesting levels. The if statement increases the nesting level, which demands a corresponding indentation increase if you go onto a new line; the statement you describe is illegal because the 'if' isn't allowed to not be at the beginning of the line, but it's unambiguous. Of course, since Python lacks a non-whitespace way of indicating the end of an if block, there's no way to put your if A and if B onto the same line as peers. But that's a consequence of a design decision, and one that can't easily be changed. Every language has warts like that; eschewing variable declarations prevents infinite nesting of scopes, but demanding variable declarations makes interactive work harder. To paraphrase the Pirate King: Always follow the dictates of your conscience, and accept the consequences. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On 13 October 2012 19:41, Chris Angelico ros...@gmail.com wrote: On Sun, Oct 14, 2012 at 5:21 AM, Joshua Landau joshua.landau...@gmail.com wrote: Because Python uses indentation, what would if A: print(1); if B: print(2) even do? It has to fail, because we have to assume consistent indentation for ;s*. With \n as I proposed, you still have to indent: it is just a method to bypass lame shells [it would become if A: print(1)\nif B: print(2)]. sikorsky@sikorsky:~/cpython$ python -c if False: print(1); print(2) sikorsky@sikorsky:~/cpython$ python -c if True: print(1); print(2) 1 2 sikorsky@sikorsky:~/cpython$ The semicolon separates statements, but doesn't change nesting levels. The if statement increases the nesting level, which demands a corresponding indentation increase if you go onto a new line; the statement you describe is illegal because the 'if' isn't allowed to not be at the beginning of the line, but it's unambiguous. Of course, since Python lacks a non-whitespace way of indicating the end of an if block, there's no way to put your if A and if B onto the same line as peers. But that's a consequence of a design decision, and one that can't easily be changed. Every language has warts like that; eschewing variable declarations prevents infinite nesting of scopes, but demanding variable declarations makes interactive work harder. To paraphrase the Pirate King: Always follow the dictates of your conscience, and accept the consequences. I get what you're saying, but I think my point is largely unchanged. When I said *You could have some rules that govern ambiguities well, but none that I can think of would be both backward-compatible and complete. If it's incomplete we've just moved the goalpost*. I was referring to exactly this (and a couple of other options). By allowing these we're just adding a confusing way of introducing layers - we've still got a whole lot of syntax we can't write in a single line. The fact that your proposal can't allow a=[]\nfor x in range(10): a.append(x**a[-2])\nprint(a) makes it somewhat an incomplete suggestion, and code like: while True: while True: break; break is just confusing. I don't want to sound closed, but the options I'm really open to are: a) It does a limited set of things that make a those things nicer, á la @ b) It does *almost* everything, minus some carefully-chosen things deemed to quirky, á la current newlines (which don't allow if a: if b: pass) c) It does everything that would be possible Your example falls nicely between *a* and *b*, which I do not find particularly helpful. Mine attempts *a* by only applying to python -c, but would be *c* if it didn't. I find the syntax to horrible for general code, which is why I didn't suggest that. Hopefully you see what I have against this suggestion, but also that I agree there is a problem and that there may well be a good way to fix it. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On Sun, Oct 14, 2012 at 6:06 AM, Joshua Landau joshua.landau...@gmail.com wrote: The fact that your proposal can't allow a=[]\nfor x in range(10): a.append(x**a[-2])\nprint(a) makes it somewhat an incomplete suggestion, and code like: while True: while True: break; break is just confusing. Agreed. However, I don't think there's going to be _any_ perfect solution for delimiting blocks, short of from __future__ import braces. I don't want to sound closed, but the options I'm really open to are: a) It does a limited set of things that make a those things nicer, á la @ b) It does almost everything, minus some carefully-chosen things deemed to quirky, á la current newlines (which don't allow if a: if b: pass) c) It does everything that would be possible Your example falls nicely between a and b, which I do not find particularly helpful. Mine attempts a by only applying to python -c, but would be c if it didn't. I find the syntax to horrible for general code, which is why I didn't suggest that. Your idea is an extension to the -c parameter that would technically work, but be fairly hard to manage in anything other than the trivial case. My idea is an extension to general syntax that would work in all cases where you aren't trying to put a statement after the end of what would be an indented block. Both have their limitations, but both would be - as far as I can see - backward compatible. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use while within the command in -c option of python?
On 13 October 2012 22:39, Chris Angelico ros...@gmail.com wrote:
On Sun, Oct 14, 2012 at 6:06 AM, Joshua Landau
joshua.landau...@gmail.com wrote:
The fact that your proposal can't allow a=[]\nfor x in range(10):
a.append(x**a[-2])\nprint(a) makes it somewhat an incomplete suggestion,
and code like:
while True: while True: break; break
is just confusing.
Agreed. However, I don't think there's going to be _any_ perfect
solution for delimiting blocks, short of from __future__ import
braces.
I don't know. I don't personally think of it as much of a problem, as the
only time this will ever really cause trouble is:
a) You can't enter newlines easily
b) It's a hassle to keep track of indentation
These only really apply to a few things.
I don't want to sound closed, but the options I'm really open to are:
a) It does a limited set of things that make a those things nicer, á la
@
b) It does almost everything, minus some carefully-chosen things deemed
to
quirky, á la current newlines (which don't allow if a: if b: pass)
c) It does everything that would be possible
Your example falls nicely between a and b, which I do not find
particularly
helpful. Mine attempts a by only applying to python -c, but would be c
if
it didn't. I find the syntax to horrible for general code, which is why I
didn't suggest that.
Your idea is an extension to the -c parameter that would technically
work, but be fairly hard to manage in anything other than the trivial
case. My idea is an extension to general syntax that would work in all
cases where you aren't trying to put a statement after the end of what
would be an indented block. Both have their limitations, but both
would be - as far as I can see - backward compatible.
Since you seem to want to solve the general case (I was under the
assumption that we were still only talking in the context of the OP) I have
an idea.
There could be a Python module that reads a file like this:
if a: ${ print(1) $ print(2) $ while b: c() $ if g: ${ pass }$ }$ print(d)
and transforms it to the valid Python:
if a:
print(1)
print(2)
while b: c()
if g:
pass
print(d)
That is *also* callable from the command-line like so:
python -m debrace -c if a: ${ print(1) $ print(2) $ while b: c() $ if g:
${ pass }$ }$ print(d)
This should solve both *a* and *b* above, and it would make life easier for
scripters. It's also easy to mock up, and from then we only need it in the
stdlib.
~~~
${ means INDENT
}$ means DEDENT
$ means NEWLINE (similar to ;)
*$ has a lower precedence than ${ or }$*
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Re: How to use while within the command in -c option of python?
On Sun, Oct 14, 2012 at 9:00 AM, Joshua Landau
joshua.landau...@gmail.com wrote:
That is also callable from the command-line like so:
python -m debrace -c if a: ${ print(1) $ print(2) $ while b: c() $ if g:
${ pass }$ }$ print(d)
Wait you're pretty much implementing from __future__ import braces?
ChrisA
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Re: How to use while within the command in -c option of python?
On 13 October 2012 23:09, Chris Angelico ros...@gmail.com wrote:
On Sun, Oct 14, 2012 at 9:00 AM, Joshua Landau
joshua.landau...@gmail.com wrote:
That is also callable from the command-line like so:
python -m debrace -c if a: ${ print(1) $ print(2) $ while b: c() $ if
g:
${ pass }$ }$ print(d)
Wait you're pretty much implementing from __future__ import braces?
But *without changing Python*. The Python that's run is brace-less. This is
a *pure module* and thus none of this will occur inside code, just in its
generation or on the command line.
Unless you want to use it on all of your files, in which case you're better
off with another language.
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How to use while within the command in -c option of python?
python -c import os; while True: print('hello')
File string, line 1
import os; while True: print('hello')
^
SyntaxError: invalid syntax
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Re: How to use while within the command in -c option of python?
On Fri, 12 Oct 2012 15:51:19 -0700
Herman sorsor...@gmail.com wrote:
python -c import os; while True: print('hello')
File string, line 1
import os; while True: print('hello')
^
SyntaxError: invalid syntax
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You get a syntax error since you didn't used tabs indents in your string
which is normal for python AFAIK.
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Re: How to use while within the command in -c option of python?
On 10/12/2012 06:51 PM, Herman wrote:
python -c import os; while True: print('hello')
File string, line 1
import os; while True: print('hello')
^
SyntaxError: invalid syntax
See the recent thread:
for-loop on cmd-line
The problem has nothing to do with the command line, it's caused by
trying to use a keyword 'while' somewhere other than the beginning of
the statement.
I'll ask you the same question I had: why do you bother? What's wrong
with making a separate file for the source code?
But as for solutions, first question is what OS you're running on. If
not Windows, you can probably use \n at appropriate points.
If that's not good enough, what about simply running the script instead
of a batch file?
If that's not good enough, how about merging the two languages, with a
trick like starting the python code with rem = followed by the
shell script?
There are many others, but we cannot choose without knowing your other
constraints.
--
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Re: How to use while within the command in -c option of python?
On Fri, 12 Oct 2012 19:04:20 -0400, Etienne Robillard wrote:
On Fri, 12 Oct 2012 15:51:19 -0700
Herman sorsor...@gmail.com wrote:
python -c import os; while True: print('hello') File string,
line 1
import os; while True: print('hello')
^
SyntaxError: invalid syntax
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You get a syntax error since you didn't used tabs indents in your string
which is normal for python AFAIK.
Incorrect. Python lets you use either spaces or tabs for indents, and in
this case the SyntaxError is BEFORE the missing indent. He gets
SyntaxError because you can't follow a semicolon with a statement that
begins a block. It's the `while` that causes the error, not the lack of
indent. Here's an example with `if` and an indented block that also
fails:
[steve@ando ~]$ python -c pass; pass
[steve@ando ~]$ python -c pass; if True:pass
File string, line 1
pass; if True: pass
^
SyntaxError: invalid syntax
Solution: don't use semi-colons, use newlines.
In this example, I use `Ctrl-Q ENTER` to insert a literal newline in the
string, which shows as ^M. Note that you *cannot* just type ^ M (caret
M), that won't work, it must be an actual control character.
[steve@ando ~]$ python -c 'import time^Mwhile True:^Mprint(hello);
time.sleep(2)'
hello
hello
hello
Traceback (most recent call last):
File string, line 3, in module
KeyboardInterrupt
In this example I just hit the Enter key to insert a newline, and let the
shell deal with it. The marks are part of the shell's prompt.
[steve@ando ~]$ python -c import time
while True:
print('hello'); time.sleep(2)
hello
hello
hello
Traceback (most recent call last):
File string, line 3, in module
KeyboardInterrupt
--
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Re: How to use while within the command in -c option of python?
I was just trying to do in a shell to quickly monitor a file. Imagine
instead of printing hello, it is os.system(cat somefile), etc.
Look like it works if i press an enter after the import xxx. Thanks.
On Fri, Oct 12, 2012 at 5:29 PM, Dave Angel d...@davea.name wrote:
On 10/12/2012 06:51 PM, Herman wrote:
python -c import os; while True: print('hello')
File string, line 1
import os; while True: print('hello')
^
SyntaxError: invalid syntax
See the recent thread:
for-loop on cmd-line
The problem has nothing to do with the command line, it's caused by
trying to use a keyword 'while' somewhere other than the beginning of
the statement.
I'll ask you the same question I had: why do you bother? What's wrong
with making a separate file for the source code?
But as for solutions, first question is what OS you're running on. If
not Windows, you can probably use \n at appropriate points.
If that's not good enough, what about simply running the script instead
of a batch file?
If that's not good enough, how about merging the two languages, with a
trick like starting the python code with rem = followed by the
shell script?
There are many others, but we cannot choose without knowing your other
constraints.
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DaveA
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Re: How to use while within the command in -c option of python?
In article
canoe_mi+vew6t0ec-kcohouxn7o2a8v6qbbzrzqryvzi+b7...@mail.gmail.com,
Herman sorsor...@gmail.com wrote:
I was just trying to do in a shell to quickly monitor a file. Imagine
instead of printing hello, it is os.system(cat somefile), etc.
Look like it works if i press an enter after the import xxx. Thanks.
If you are using a POSIX-compatible shell, the canonical approach for
use cases like this is to use a here document, for example:
python - EOF
import os
while True:
print('hello')
EOF
The - tells the Python interpreter to read from stdin. The shell
supplies the lines between the EOF and the matching EOF as stdin.
http://en.wikipedia.org/wiki/Here_document
--
Ned Deily,
n...@acm.org
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