Re: Creating a local variable scope.

[r0g]

Ben Finney wrote:
> markolopa  writes:
> 
>> Hi Roger,
>>
> […]
>>> Long, descriptive variable names all_in_lower_case
>>> Function names all in CamelCase
>>> Global names are in ALL CAPS
>> yes, pep8 I guess.
> 
> Not quite: it deviates from PEP 8 on function names, which should rather
> be ‘lower_case_words_separated_by_underscores’.
> 
> The ‘UPPER_CASE_WORDS_WITH_UNDERSCORES’ form is for “constants”, i.e.
> names that indicate they should stay bound to the same value through the
> life of the program (which is the closest normal Python programs get to
> a “constant” binding).
> 
> The ‘TitleCase’ form should be used only for class names.
> 
> The ‘camelCase’ form is not conformant with PEP 8 at all (which makes me
> glad, since it's hideous).
> 


Heh, see! It's a spiky subject ;) Someday I'm going to found a
substantial open source project just so I can force subsequent
contributors to format their code the way I like it! *bwahahahaaa* :)


Roger.

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Re: Beginner Q. interrogate html object OR file search?

[Steven D'Aprano]

On Wed, 02 Dec 2009 19:24:07 -0800, Mark G wrote:

> Hi all,
> 
> I am new to python and don't yet know the libraries well. What would be
> the best way to approach this problem: I have a html file parsing script
> - the file sits on my harddrive. I want to extract the date modified
> from the meta-data. Should I read through lines of the file doing a
> string.find to look for the character patterns of the meta- tag, 

That will probably be the fastest, simplest, and easiest to develop. But 
the downside is that it will be subject to false positives, if some tag 
happens to include text which by chance looks like your meta-data. So, 
strictly speaking, this approach is incorrect.

> or
> should I use a DOM type library to retrieve the html element I want?
> Which is best practice? 

"Best practice" would imply DOM.

As for which you use, you need to weigh up the risks of a false positive 
versus the convenience and speed of string matching versus the 
correctness of a DOM approach.


> which occupies least code?

Unless you're writing for an embedded system, or if the difference is 
vast (e.g. 300 lines versus 30) that's premature optimization.

Personally, I'd use string matching or a regex, and feel guilty about it.



-- 
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Re: Bored.

[r0g]

Necronymouse wrote:
> Thanks for reaction, I will prohably choose some project as you
> said...
> 
> 
> 


If you want to dip your toe in waters of open source contribution it
looks like Gitso could use a little help pushing out their 0.6 release
(which I just happen to quite want but don't have time to get involved
in right now ;)


Roger.
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Re: Beginner Q. interrogate html object OR file search?

[r0g]

Mark G wrote:
> Hi all,
> 
> I am new to python and don't yet know the libraries well. What would
> be the best way to approach this problem: I have a html file parsing
> script - the file sits on my harddrive. I want to extract the date
> modified from the meta-data. Should I read through lines of the file
> doing a string.find to look for the character patterns of the meta-
> tag, or should I use a DOM type library to retrieve the html element I
> want? Which is best practice? which occupies least code?
> 
> Regards, Mark


Beautiful soup is the html parser of choice partly as it handles badly
formed html well.

http://www.crummy.com/software/BeautifulSoup/


If the date info occurs at a consistent offset from the start of the tag
then you can use simple string slicing to snip out the date. If not
then, as others suggest, regex is your friend.

If you need to convert a date/time string back into a unix style
timestamp chop the string into bits, put them into a tuple of length 9
and give that to time.mktime()...

def time_to_timestamp( t ):
return time.mktime( (int(t[0:4]), int(t[5:7]), int(t[8:10]),
int(t[11:13]), int(t[14:16]), int(t[17:19]), 0, 0, 0) )

Note the last 3 values are hardcoded to 0, this is because most
date/time strings I deal with do not encode sub second information, only
 /MM/DD h:m:s


Roger.
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Re: how to debug extended module?

[junyoung]

On 12월2일, 오전9시54분, junyoung  wrote:
> On 12월1일, 오후6시14분, "Diez B. Roggisch"  wrote:
>
>
>
>
>
> > junyoung schrieb:
>
> > > Hi, I am a newbie who want to implement a extend module to use native
> > > python language with my own shared library.
>
> > If it's a C shared library, don't bother extending it. Use ctypes to
> > wrap it. Much easier, and no need for a compiler.
>
> > > to test wrapper library(extend module, name is 'test.so'), I created
> > > some test-cases.
>
> > > There are some errors what I couldn't figure our reasons.
>
> > > ex)
> > > SystemError: error return without exception set
> > > 
> > > ...
>
> > This indicates that you violated the exception protocol.
>
> >http://docs.python.org/c-api/exceptions.html
>
> > > so, I ran the ddd with python and then I set test.py as a argument of
> > > it.
>
> > > ex)
> > > ddd python
>
> > > in ddd
> > > run with arguments : test.py
>
> > > but in this situation, I couldn't step in my own shared library
> > > (compiled as the debug mode).
>
> > > Is there any clear way to debug my extend module(that it, debug shared
> > > library)??
>
> > I do it like this:
>
> > # gdb python
> > gdb $ set args test.py
> > gdb $ run
>
> > You can only debug a binary program (test.py isn't one, python is). But
> > trough the args, you get yours script running.
>
> > It *might* help to have a python debug build, I personally never needed
> > that.
>
> > Diez
>
> here is my results. anyway, check this out.
>
> (gdb) set args connect.py
> set args connect.py
> (gdb) run
> run
> Starting program: /usr/bin/python connect.py
> (no debugging symbols found)
> (no debugging symbols found)
> (no debugging symbols found)
> [Thread debugging using libthread_db enabled]
> (no debugging symbols found)
> (no debugging symbols found)
> (no debugging symbols found)
> (no debugging symbols found)
> [New Thread 0x7f619747e6e0 (LWP 23683)]
> (no debugging symbols found)
> (no debugging symbols found)
> (no debugging symbols found)
> (no debugging symbols found)
> [New Thread 0x415a9950 (LWP 23686)]
> [Thread 0x415a9950 (LWP 23686) exited]
> [New Thread 0x415a9950 (LWP 23687)]
> [Thread 0x415a9950 (LWP 23687) exited]
> Traceback (most recent call last):
>   File "connect.py", line 25, in 
> main()
>   File "connect.py", line 18, in main
> connection_test()
>   File "connect.py", line 15, in connection_test
> cnxn.close()
> SystemError: error return without exception set
>
> Program exited with code 01.
> (gdb)
>
> as you see, I can't load symbol table information from gdb.
>
> now python is defaulted installed as release.
>
> my os is ubuntu
> the python is installed in /usr/bin
> the python version is 2.5.1
>
> do i need to re-install python as debug mode?

after compiling it(python) as debug mode, I could debug it ;(

I don't still know why I have to compile it as debug mode to step in
my own library. interesting
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Re: Beginner Q. interrogate html object OR file search?

[Stephen Hansen]

On Wed, Dec 2, 2009 at 7:24 PM, Mark G  wrote:

> Hi all,
>
> I am new to python and don't yet know the libraries well. What would
> be the best way to approach this problem: I have a html file parsing
> script - the file sits on my harddrive. I want to extract the date
> modified from the meta-data. Should I read through lines of the file
> doing a string.find to look for the character patterns of the meta-
> tag, or should I use a DOM type library to retrieve the html element I
> want? Which is best practice? which occupies least code?
>
>
You can probably do some string.find's and it might work almost always, HTML
is funky and quite often coded badly by bad people.

And I would never personally suggest anyone go anywhere near a DOM library,
their life will never be happy again :)

I'd get lxml -- even though you're not directly using xml. It has a html
package in it too, its fast and astoundingly easy to use and fantastically
featureful for future growth :)

http://codespeak.net/lxml/lxmlhtml.html

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Re: Beginner Q. interrogate html object OR file search?

[Mark G]

On Dec 3, 4:19 pm, inhahe  wrote:
> or i guess you could go the middle-way and just use regex.
> people generally say don't use regex for html (regex can't do the
> nesting), but it's what i would do in this case.
> though i don't exactly understand the question, re the html file
> parsing script you say you have already, or how the date is 'modified
> from' the meta-data.
>
> On Wed, Dec 2, 2009 at 10:24 PM, Mark G  wrote:
> > Hi all,
>
> > I am new to python and don't yet know the libraries well. What would
> > be the best way to approach this problem: I have a html file parsing
> > script - the file sits on my harddrive. I want to extract the date
> > modified from the meta-data. Should I read through lines of the file
> > doing a string.find to look for the character patterns of the meta-
> > tag, or should I use a DOM type library to retrieve the html element I
> > want? Which is best practice? which occupies least code?
>
> > Regards, Mark
> > --
> >http://mail.python.org/mailman/listinfo/python-list
>
>

I'm tempted to use regex too. I have done a bit of perl & bash, and
that is how I would do it with those.

However, I thought there would be a smarter way to do it with
libraries. I have done some digging through the libraries and think I
can do it with xml.dom.minidom. Here is what I want to try...

# if html file already exists, inherit the created date
# 'output' is the filename for the parsed file
html_xml = xml.dom.minidom.parse(output)
for node in html_xml.getElementsByTagName('meta'):  # visit every
node 
#debug print node.toxml()
metatag_type = nodes.attributes["name"]
if metatag_type.name == "DC.Date.Modified":
metatag_date = nodes.attributes["content"]
date_created = metatag_date.value()
print date_created

I haven't quite got up to hear in my debugging. I'll let you know if
it works...

RE: your questions. 1) I already have the script in bash - wanting to
convert to Python :) I'm half way through
I want to extract the value of the tag 

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Re: Beginner Q. interrogate html object OR file search?

[inhahe]

or i guess you could go the middle-way and just use regex.
people generally say don't use regex for html (regex can't do the
nesting), but it's what i would do in this case.
though i don't exactly understand the question, re the html file
parsing script you say you have already, or how the date is 'modified
from' the meta-data.

On Wed, Dec 2, 2009 at 10:24 PM, Mark G  wrote:
> Hi all,
>
> I am new to python and don't yet know the libraries well. What would
> be the best way to approach this problem: I have a html file parsing
> script - the file sits on my harddrive. I want to extract the date
> modified from the meta-data. Should I read through lines of the file
> doing a string.find to look for the character patterns of the meta-
> tag, or should I use a DOM type library to retrieve the html element I
> want? Which is best practice? which occupies least code?
>
> Regards, Mark
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: Declaring a class level nested class?

[inhahe]

it seems to me like it should work just fine if you just take out the
second line where it just says nestedClass

On Wed, Dec 2, 2009 at 11:55 PM, cmckenzie  wrote:
> Hi.
>
> I'm new to Python, but I've managed to make some nice progress up to
> this point. After some code refactoring, I ran into a class design
> problem and I was wondering what the experts thought. It goes
> something like this:
>
> class module:
>   nestedClass
>
>   def __init__():
>      self.nestedClass = nested()
>      print self.nestedClass.nestedVar
>
>   class nested():
>      nestedVar = 1
>      def __init__(self):
>         print "Initialized..."
>
> I can't figure out what the correct way to construct the "nested"
> class so it can belong to "module".
>
> I want a class level construct of "nested" to belong to "module", but
> I keep getting nestedClass isn't defined.
>
> My example isn't great or 100% accurate, but I hope you get the idea.
>
> Thanks.
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: Declaring a class level nested class?

[Chris Rebert]

On Wed, Dec 2, 2009 at 8:55 PM, cmckenzie  wrote:
> Hi.
>
> I'm new to Python, but I've managed to make some nice progress up to
> this point. After some code refactoring, I ran into a class design
> problem and I was wondering what the experts thought. It goes
> something like this:
>
> class module:
>   nestedClass
>
>   def __init__():
>      self.nestedClass = nested()
>      print self.nestedClass.nestedVar
>
>   class nested():
>      nestedVar = 1
>      def __init__(self):
>         print "Initialized..."
>
> I can't figure out what the correct way to construct the "nested"
> class so it can belong to "module".
>
> I want a class level construct of "nested" to belong to "module", but
> I keep getting nestedClass isn't defined.

Here's the scoping reason why it fails (remember that the nested class
is a class variable of the containing class):



Why do I get errors when accessing class variables (a.k.a. static variables)?
-
If you try something like the following::

class Foo(object):
class_variable = 42

def method(self, x):
return x + class_variable


Foo().method(7)

You'll get an error about Python being unable to find the class variable::

Traceback (most recent call last):
 ...
NameError: global name 'class_variable' is not defined

This is because class-level scope is not consulted when looking up
plain names in methods.  When looking up a name, the following scopes
are consulted, in order: Local variables, Variables in nested
functions, Global variables, and finally, Built-ins.

To refer to class variables, you must be more explicit. There are several
ways to go about it:

* Refer to the class by name::

def method1(self, x):
return x + Foo.class_variable

* Refer to the class of the object dynamically. If you class is
subclassed, this will allow the subclasses to override the value of
the class variable. ::

def method2(self, x):
return x + self.__class__.class_variable

* Exploit the fact that attribute lookups on an object fall back to
its class. Be warned that if you have both instance and class variables
with the same name, the instance variable will shadow
the class variable. ::

def method3(self, x):
return x + self.class_variable

* If your method is not truly an instance method
(i.e. does not utilize ``self``), make it a class method ::

@classmethod
def method4(cls, x):
return x + cls.class_variable



However, there's pretty much no reason to nest classes anyway in
Python (it's not Java!). Just make them both top-level in the file. If
one class is only used internally in the module, just use the normal
private naming convention of starting its name with an underscore.

Also note that class names should generally use StudlyCaps, and that
naming a class "module" is rather confusing.

Cheers,
Chris
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Declaring a class level nested class?

[cmckenzie]

Hi.

I'm new to Python, but I've managed to make some nice progress up to
this point. After some code refactoring, I ran into a class design
problem and I was wondering what the experts thought. It goes
something like this:

class module:
   nestedClass

   def __init__():
  self.nestedClass = nested()
  print self.nestedClass.nestedVar

   class nested():
  nestedVar = 1
  def __init__(self):
 print "Initialized..."

I can't figure out what the correct way to construct the "nested"
class so it can belong to "module".

I want a class level construct of "nested" to belong to "module", but
I keep getting nestedClass isn't defined.

My example isn't great or 100% accurate, but I hope you get the idea.

Thanks.
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Re: Delaunay triangulation

[Vincent Davis]

Thanks for all the replies I will look at each.

  *Vincent Davis
720-301-3003 *
vinc...@vincentdavis.net
 my blog  |
LinkedIn


On Wed, Dec 2, 2009 at 10:20 AM, sturlamolden  wrote:

> On 2 Des, 15:28, David Robinow  wrote:
> > On Tue, Dec 1, 2009 at 8:31 PM, Vincent Davis 
> wrote:
> > > Anyone know of a python implementation of Delaunay triangulation?
> >
> > Matplotlib has one.
> > There's also Delny  @pypi
> >
> > It's been several years since I needed this. I can't remember the
> pros/cons.
>
> There is also a skikit add-on to NumPy/SciPy.
>
> http://scikits.appspot.com/delaunay
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Re: Help in wxpython

[Krishnakant]

On Wed, 2009-12-02 at 00:20 -0800, madhura vadvalkar wrote:
> Hi
> 
> I am trying to write an  PAINT like application where on the mouse
> click a circle is drawn on canvas. I am new to python and using
> wxpython to create this.
> 
> here is the code:
> 
> import wx
> 
> class SketchWindow(wx.Window):
> 
> def __init__ (self, parent,ID):
> 
> wx.Window.__init__(self, parent, ID)
> 
> self.panel =wx.Panel(self, size= (350,350))
> self.pen=wx.Pen( 'blue',4)
> self.pos=(0,0)
> self.InitBuffer()
> self.Bind(wx.EVT_LEFT_DOWN,self.OnLeftDown)
> 
> def InitBuffer(self):
> 
> size=self.GetClientSize()
> self.Buffer=wx.EmptyBitmap(size.width,size.height)
> dc=wx.BufferedDC(None,self.buffer)
> dc.SetBackground(wx.Brush(self.GetBackgroundColour()))
> dc.Clear()
> self.Drawcircle(dc)
> self.reInitBuffer=False
> 
> def OnLeftDown(self,event):
> self.pos=event.GetPositionTuple()
> self.CaptureMouse()
> 
> def Drawcircle(self,dc):
> pen=wx.Pen(colour,thickness,wx.SOLID)
> dc.SetPen(pen)
> dc.DrawCircle(self.pos.x,self.pos.y,r)
> 
> class SketchFrame(wx.Frame):
> def __init__(self, parent):
> 
> wx.Frame.__init__(self, parent, -1, "Sketch Frame",size=(800,600))
> self.sketch = SketchWindow(self, -1)
> 
> if __name__=='__main__':
> app=wx.PySimpleApp()
> frame=SketchFrame(None)
> frame.Show(True)
> app.MainLoop()
> 
> I am getting the following error:
> 
> Traceback (most recent call last):
>   File "C:/Python26/circle.py", line 42, in 
> frame=SketchFrame(None)
>   File "C:/Python26/circle.py", line 38, in __init__
> self.sketch = SketchWindow(self, -1)
>   File "C:/Python26/circle.py", line 12, in __init__
> self.InitBuffer()
>   File "C:/Python26/circle.py", line 19, in InitBuffer
> dc=wx.BufferedDC(None,self.buffer)
> AttributeError: 'SketchWindow' object has no attribute 'buffer'
> 
> Please tell me what I am doing wrong.
> 
> Thanks
Madhura, Sorry to be a bit off-topic, but, I would really recommend you
to use pygtk instead of wx.
For one thing, the developers at pygtk are very active (they have their
mailing list as well ) and it comes by default with python on almost all
linux distros.  You can also easily install it on windows.

Most important, the api for pygtk is closely similar to wx.
Not to mention the quick responses you will get with pygtk related
problems.

Happy hacking.
Krishnakant.

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Beginner Q. interrogate html object OR file search?

[Mark G]

Hi all,

I am new to python and don't yet know the libraries well. What would
be the best way to approach this problem: I have a html file parsing
script - the file sits on my harddrive. I want to extract the date
modified from the meta-data. Should I read through lines of the file
doing a string.find to look for the character patterns of the meta-
tag, or should I use a DOM type library to retrieve the html element I
want? Which is best practice? which occupies least code?

Regards, Mark
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Re: Question on Python as career

[Roy Smith]

joy99  wrote:

> Dear Group,
> 
> I am a researcher in India's one of the premier institutes.(Indian
> Institute of Science,Bangalore).
> [...]
> I have developed them either in Python2.5 and Python2.6.
> 
> After I complete my Post Doctoral which may be only 2-3 months away,
> with this knowledge can I join IT?
> Or Do I have to learn anything new?

The short answer is, you will always need to keep learning new things.  
Whatever set of technologies are popular today (check out 
http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html, for 
example), will change over time.

When I started out, I knew C and Fortran.  I'm amazed that C is still the 
#2 language, and Fortran isn't even on the TIOBE top 20 list any more.  17 
of the 20 didn't even exist when I started out.
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Re: [Twisted-Python] ANN: Twisted 9.0.0

[Tim Allen]

exar...@twistedmatrix.com wrote:
> A message with some ticket links from a thread on the twisted-python 
> mailing list: http://bit.ly/8csFSa

Some of those tickets seem out of date; a better plan would be to query
for tickets with the "py3k" keyword:

http://twistedmatrix.com/trac/search?q=py3k&noquickjump=1&ticket=on

I believe #2484 is the master ticket:

http://twistedmatrix.com/trac/ticket/2484


signature.asc
Description: PGP signature
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Re: prolog with python

[Chris Rebert]

On Wed, Dec 2, 2009 at 6:47 PM, William Heath  wrote:
> Hi All,
>
> I have the following prolog program that I would really like to be able to
> run in python in some elegant way:

>From googling:

http://pyke.sourceforge.net/
http://code.activestate.com/recipes/303057/

Cheers,
Chris
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prolog with python

[William Heath]

Hi All,

I have the following prolog program that I would really like to be able to
run in python in some elegant way:

q00(X01, R):-  write('Are you over 80?'), read(INPUT), write(''), q11(INPUT,
R).
q11(X11, R):-  X11=y, write(' You are passed the hardest year'), !.
q00(X01, R):-  write('You are not over 80'),

Most of the implementations I have seen use assert's and don't appear to
handle backtracking or negation.  I somehow need to provide input to the
rules as well as you can see above.  Anyone know how to do this well using a
python library?  I would love a 100% python solution if I could find one.
Anyway, thanks!

-Tim
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Re: ANN: Twisted 9.0.0

[exarkun]

On 12:18 am, tjre...@udel.edu wrote:

Christopher Armstrong wrote:

= Twisted 9.0.0 =

I'm happy to announce Twisted 9, the first (and last) release of
Twisted in 2009. The previous release was Twisted 8.2 in December of
2008. Given that, a lot has changed!

This release supports Python 2.3 through Python 2.6, though it is the
last one that will support Python 2.3. The next release will support
only Python 2.4 and above. Twisted: the framework of the future!


Not unless it supports 3.1+. Is that in the cards (tickets)?


Somewhat.

A description of the plan on stackoverflow: http://bit.ly/6hWqYU

A message with some ticket links from a thread on the twisted-python 
mailing list: http://bit.ly/8csFSa


Jean-Paul
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How to implement Varient/Tagged Unions/Pattern Matching in Python?

[metal]

I want to get pattern matching like OCaml in python(ref:http://
en.wikipedia.org/wiki/Tagged_union)

I consider the syntax:

def decl():
def Plus(expr, expr): pass
def Minus(expr, expr): pass
def Times(expr, expr): pass
def Divide(expr, expr): pass
def Value(str): pass
@enum
def expr(Plus, Minus, Times, Divide, Value): pass
declare_types(locals())

def f(e):
def _Plus(l, r):
return '(%s+%s)' % (l, r)
def _Minus(l, r):
return '(%s-%s)' % (l, r)
def _Times(l, r):
return '(%s*%s)' % (l, r)
def _Divide(l, r):
return '(%s/%s)' % (l, r)
def _Value(x):
return x
try:
match(e, locals()) # visitor pattern
except NoMatchedError:
pass

>>> print f(Times(Value("n"), Plus(Value("x", Value("y"
(n*(x+y))


But it's hard to do with nested matching. Any suggestions would be
appreciated


BTW, Please don't ask "Why do you want to do like this"
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Antoine Pitrou]

Le Tue, 01 Dec 2009 06:03:36 -0800, Mark Summerfield a écrit :
> I've produced a 4 page document that provides a very concise summary of
> Python 2<->3 differences plus the most commonly used new Python 3
> features. It is aimed at existing Python 2 programmers who want to start
> writing Python 3 programs and want to use Python 3 idioms rather than
> those from Python 2 where the idioms differ.
[...]
> 
> It is available as a free PDF download (no registration or anything)
> from InformIT's website. Here's the direct link:

This is great!

Just one thing:

« Copyright © Qtrac Ltd. 2009. All rights reserved »

Might I suggest that you release it under a free license instead?
(such as the CC by, CC by-sa, or the Free Art License)

Regards

Antoine.

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Re: How to set object parameters nicely?

[allen.fowler]

On Dec 2, 6:36 pm, Carl Banks  wrote:

> For the record, I don't really agree that a lot of parameters is code
> smell.  It's maybe a red flag that you are doing too much in one
> function and/or class, but nothing inherently shady.
>
> One thing to ask yourself: are there a lot of combinations of
> parameters that don't make sense?  For example, do you have a lot of
> cases where, say, if one parameter is set to x, then parameters a, b,
> c, and d do nothing?  That would indicate that you should break your
> function/class up into smaller, more targeted parts.
>
> However, if all your parameters are orthogonal, that is, if all or
> most combinations make sense, then there's no reason ten or twenty
> parameters isn't perfectly reasonable.
>
> Whenever I have ten parameters in an __init__, I ususally just write
> out the assignments, although more often than not the object's
> attributes don't correspond to the parameters one-to-one, so I'd have
> to write them out anyway.
>

Thank you for the thoughtful insight.

In this case, and I am trying to create a number of ORM-like objects.
(Though, there is no database involved.)

So, instances of these classes are acting as records that are shuttled
around in the system, and the object's properties are acting as
values.  The parameters are (mostly) orthogonal, but do need defaults,
and some must be required.


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Re: python bijection

[Aahz]

In article <9a6902a1-327e-435e-8c9a-b69028994...@u20g2000vbq.googlegroups.com>,
Joshua Bronson   wrote:
>
>At any rate, apologies to the community for my heteronormative
>example. It was merely pedagogical and reflects nothing about my
>personal views! If you have any further concerns, please send them to
>my lawyer, /dev/null.

Apology accepted.  ;-)
-- 
Aahz (a...@pythoncraft.com)   <*> http://www.pythoncraft.com/

The best way to get information on Usenet is not to ask a question, but
to post the wrong information.  
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Re: ANN: Twisted 9.0.0

[Terry Reedy]

Christopher Armstrong wrote:

= Twisted 9.0.0 =

I'm happy to announce Twisted 9, the first (and last) release of
Twisted in 2009. The previous release was Twisted 8.2 in December of
2008. Given that, a lot has changed!

This release supports Python 2.3 through Python 2.6, though it is the
last one that will support Python 2.3. The next release will support
only Python 2.4 and above. Twisted: the framework of the future!


Not unless it supports 3.1+. Is that in the cards (tickets)?

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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Terry Reedy]

Mark Summerfield wrote:


Well it seems clear to me that the BDFL wants to kill of % formatting,
but wasn't able to for Python 3...


Definitely. I thought of adding autonumbering of fields (in 3.1) in 
response to his inquiry about the barriers to moving to .format. That 
solved 'simplicity of defaults'. The other, 'Autoconversion of installed 
base' still awaits.



So I still think it is reasonable
(1) to describe it as deprecated and (2) to only teach and use
str.format().


At the moment (3.1) there are, unfortunately, library packages that 
require % for formatting (logging, I believe, for one). There has been 
discussion on adding a new option for 3.2, but I do not know what will 
happen. Depends on whether you want to be absolutely complete. I 
strictly use .format when I can, which so far is always.


Terry Jan Reedy

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Re: Cron Job Output

[LoD MoD]

You might try something like this http://code.activestate.com/recipes/157035/


On Wed, Dec 2, 2009 at 3:05 PM, baytes  wrote:
> I have cron checking services every 5-10 minutes, and if a service
> goes up or down it writes to a file, Im trying to write a script that
> will check that file for updates and print the results. this will tie
> into a module for phenny where the bot will be able to print the
> contents of the updated file to the channel.
>
> Im extremely new to python and any point in the right direction or
> tutorials on the subject would be greatly appreicated.
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: Question about file objects...

[Terry Reedy]

J wrote:

On Wed, Dec 2, 2009 at 09:27, nn  wrote:

Is there a way to read the file, one item at a time, delimited by
commas WITHOUT having to read all 16,000 items from that one line,
then split them out into a list or dictionary??



File iteration is a convenience since it is the most common case. If
everything is on one line, you will have to handle record separators
manually by using the .read() method on the file
object and searching for the comma. If everything fits in memory the
straightforward way would be to read the whole file with .read() and
use .split(",") on the returned string. That should give you a nice
list of everything.


Agreed. The confusion came because the guy teaching said that
iterating the file is delimited by a carriage return character...


If he said exactly that, he is not exactly correct. File iteration looks 
for line ending character(s), which depends on the system or universal 
newline setting.



which to me sounds like it's an arbitrary thing that can be changed...

I was already thinking that I'd have to read it in small chunks and
search for the delimiter i want...  and reading the whole file into a
string and then splitting that would would be nice, until the file is
so large that it starts taking up significant amounts of memory.

Anyway, thanks both of you for the explanations... I appreciate the help!


I would not be surprised if a generic file chunk generator were posted 
somewhere. It would be a good entry for the Python Cookbook, if not 
there already.


tjr

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Re: python bijection

[Joshua Bronson]

On Dec 1, 9:03 pm, Chris Rebert  wrote:
> Reminds me of this quite funny blog post:
> "Gay marriage: the database engineering perspective"
> http://qntm.org/?gay

amazing
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Re: How to set object parameters nicely?

[Carl Banks]

On Dec 2, 12:13 pm, "allen.fowler"  wrote:
> > >>> Is there a better way to do this?
> > >> class MyOb(object):
> > >>      def __init__(self, **kwargs):
> > >>          self.__dict__.update(kwargs)
>
> > >> ob1 = MyOb(p1="Tom", p3="New York")
> > >> ob2 = MyOb(p1="Joe", p2="j...@host", p3="New Jersey")
>
> > > I've tried this, but have found two issues:
>
> > > 1) I can't set default values.
> > > 2) I can't set required values.
>
> > > In both of the above cases, if theobjectis created without the
> > > "exact" dict() I expect, all the assumption my methods make about what
> > > is available in "self" fall apart.
>
> > > Perhaps, as Diez mentioned, my approach is wrong.   What would be the
> > > right thing to do in this situation?
>
> > There is no general answer to this. It depends on your actual problem.
>
> What are some of the patterns that tend to be used?

For the record, I don't really agree that a lot of parameters is code
smell.  It's maybe a red flag that you are doing too much in one
function and/or class, but nothing inherently shady.

One thing to ask yourself: are there a lot of combinations of
parameters that don't make sense?  For example, do you have a lot of
cases where, say, if one parameter is set to x, then parameters a, b,
c, and d do nothing?  That would indicate that you should break your
function/class up into smaller, more targeted parts.

However, if all your parameters are orthogonal, that is, if all or
most combinations make sense, then there's no reason ten or twenty
parameters isn't perfectly reasonable.

Whenever I have ten parameters in an __init__, I ususally just write
out the assignments, although more often than not the object's
attributes don't correspond to the parameters one-to-one, so I'd have
to write them out anyway.


Carl Banks
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Re: python bijection

[Joshua Bronson]

On Dec 1, 8:17 pm, a...@pythoncraft.com (Aahz) wrote:
> In article 
> <85100df7-a8b0-47e9-a854-ba8a8a2f3...@r31g2000vbi.googlegroups.com>,
> Joshua Bronson   wrote:
> >I noticed the phonebook example in your ActiveState recipe and thought
> >you might consider changing it to something like husbands to wives,
> >since the names-to-phone-numbers relation is many-to-many.
>
> What makes you think husbands to wives is one-to-one?  ;-)  (Even
> assuming monogamy, you have husbands-to-husbands and wives-to-wives.)

Hah! I knew this was coming and even put "assuming monogamy" in the
source!
http://bitbucket.org/jab/bidict/src/712da6e2dd26/bidict.py#cl-65  ;P

As for husbands-to-husbands and wives-to-wives, those are just
separate one-to-one mappings! Doesn't mean husbands-to-wives ain't one-
to-one!

At any rate, apologies to the community for my heteronormative
example. It was merely pedagogical and reflects nothing about my
personal views! If you have any further concerns, please send them to
my lawyer, /dev/null.
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Cron Job Output

[baytes]

I have cron checking services every 5-10 minutes, and if a service
goes up or down it writes to a file, Im trying to write a script that
will check that file for updates and print the results. this will tie
into a module for phenny where the bot will be able to print the
contents of the updated file to the channel.

Im extremely new to python and any point in the right direction or
tutorials on the subject would be greatly appreicated.
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[John Posner]

On Wed, 02 Dec 2009 13:34:11 -0500, Carsten Haese  
 wrote:




With string interpolation, you don't need to do that, either.

'%*d' % (8,456)

' 456'



Thanks, Carsten and Mark D. -- I'd forgotten about the use of "*" in  
minimum-field-width specs and precision specs (doh). How about this:


  "pi={1:.{0}f} e={2:.{0}f}".format(5, math.pi, math.e)

  (result: 'pi=3.14159 e=2.71828')

Can the Python2 %-formating facility handle this without repeating the "5"  
argument?


Even if it can, I stand by my original suggestion: include an example to  
show that the arguments to str.format() can be used on both the left and  
the right of a ":" in a replacement field.


-John
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Re: Insane Problem

[MRAB]

Victor Subervi wrote:

Hi;
I have spent 2-3 hours trying to track this bug. Here's the code snippet:

  form = cgi.FieldStorage()
  fn = getattr(options, 'products')
  ourOptionsNames = []
  optionsNames, doNotUse  = fn('names')
  for name in optionsNames:
test = table + '-' + name
print test
check = form.getfirst(test, '')
print check
if check != '':
  ourOptionsNames.append(name)
 
Now, when it looks through with test=='products', it doesn't report that 
any of the values from the form are checked. However, when I explicitly 
write out something like:

print form.getfirst('products-sizes', '')
which I checked on the form from the referring page, it does in fact 
print out! My test prints show that 'products-sizes' is being passed to 
"check" and should therefore be appended to "ourOptionsNames". But it 
isn't! What am I missing here??



What do the print statements actually print? Please copy and paste their
output.
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[MRAB]

Mark Summerfield wrote:

On 2 Dec, 19:28, David H Wild  wrote:

In article
<351fcb4c-4e88-41b0-a0aa-b3d63832d...@e23g2000yqd.googlegroups.com>,
   Mark Summerfield  wrote:


I only just found out that I was supposed to give a different URL:
http://www.informit.com/promotions/promotion.aspx?promo=137519
This leads to a web page where you can download the document (just by
clicking the "Download Now" button), but if you _choose_ you can also
enter your name and email to win some sort of prize.

There is a typographical fault on page 4 of this pdf file. The letter "P"
is missing from the word "Python" at the head of the comparison columns.



Which is page 4? The page numbers are missing! (But the column titles
look OK.) :-)


I can't see that problem---I've tried the PDF with evince, gv,
acroread, and okular, and no missing "P" on page 4. I don't have a
machine with RISC OS on it so I can't test on that environment!


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Re: Noob thread lock question

[John Nagle]

Diez B. Roggisch wrote:

Astley Le Jasper schrieb:

I have a number of threads that write to a database. I have created a
thread lock, but my question is this:

- If one thread hits a lock, do a) all the other threads stop, or b)
just the ones that come to the same lock?


Only the ones coming the the same lock.


- I presume that the answer is b. In which case do the threads stop
only if they come to the same instance of a lock. For example, you
could have a lock instance for one database and another instance for
another database (first_db_thread_lock = threading.RLock() 
second_db_thread_lock = threading.RLock()).



There is nothing like "not an instance of a lock". So it's essentially 
the same question as the first, and thus the answer is also: yes, only 
for the *same* lock, which is an instance.


Diez


   Note that if you're using MySQLdb, there are some restrictions on threading.
Only one thread at a time can use each connection to the database.  But you
can create multiple connections to the same database at the same time from
a single program, and run them concurrently.

John Nagle
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Re: Python without wrapper script

[Hans Mulder]

Ulrich Eckhardt wrote:

eric.frederich wrote:

Is there a way to set up environment variables in python itself
without having a wrapper script.


Yes, sure, you can set environment variables...


The wrapper script is now something like

#!/bin/bash

export LD_LIBRARY_PATH="/some/thing/lib:$LD_LIBRARY_PATH"
export LD_LIBRARY_PATH="/another/thing/lib:$LD_LIBRARY_PATH"

export PATH="/some/thing/bin:$PATH"
export PATH="/another/thing/bin:$PATH"

python ./someScript.py


...but this won't work, I'm afraid.

LD_LIBRARY_PATH is for the program loader / dynamic linker under Linux. This
thing is what is invoked _before_ the program is started, any later
modifications to the environment are ignored.


In cases like yours I have sometimes written Python scripts that acted as
their own wrapper:

#!/usr/bin/env python

import os, sys

if 'LD_LIBRARY_PATH' in os.environ:
lib_path = os.environ['LD_LIBRARY_PATH']
if '/some/thing/lib' in lib_path and '/another/thing/lib' in lib_path:
pass
else:
os.environ['LD_LIBRARY_PATH'] += ':/some/thing/lib:/another/thing/lib'
os.execve(sys.argv[0], sys.argv, os.environ)
else:
os.environ['LD_LIBRARY_PATH'] = '/some/thing/lib:/another/thing/lib'
os.execve(sys.argv[0], sys.argv, os.environ)

os.environ['PATH'] = '/some/thing/bin:/another/thing/bin:' + os.environ['PATH']

# At this point, you can import a module that depends
# on LD_LIBRARY_PATH including /some/thing/lib
#
# Alternatively (and more clearly), you can replace the 'pass' above
# by that import statement


This code restarts Python if it has to modify os.environ['LD_LIBRARY_PATH'].

If you try to single-step this code under pdb, you'll get as far as the
os.execve() call.  That call starts Python afresh, without a debugger.
In other words, if you need to use pdb, you'll have to set the environment
variables in the shell.


Similarly PATH, which tells the shell (e.g. bash) where to find executables.
If you need that to e.g. find 'python' itself, you're out of luck.
Otherwise, I believe Python itself doesn't use PATH, so you could set it
inside and any shells started from Python should pick it up.


You don't have to restart Python if you modify to os.environ['PATH'],
so that bit is easy.



Hope this helps,

-- HansM


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ANN: Twisted 9.0.0

[Christopher Armstrong]

= Twisted 9.0.0 =

I'm happy to announce Twisted 9, the first (and last) release of
Twisted in 2009. The previous release was Twisted 8.2 in December of
2008. Given that, a lot has changed!

This release supports Python 2.3 through Python 2.6, though it is the
last one that will support Python 2.3. The next release will support
only Python 2.4 and above. Twisted: the framework of the future!

You can download the new release at our web site,

http://twistedmatrix.com/

There were around 285 tickets resolved in this release. The full list
of changes is available here:


http://twistedmatrix.com/trac/browser/tags/releases/twisted-9.0.0/NEWS?format=raw

It's quite a huge list of changes spanning almost all of the Twisted
projects, so here are some of the more exciting changes:

In the core:
- The Windows IOCP reactor now supports SSL.
- The memcache protocol implementation got some nice new features.

In Twisted Web:
- There's a new HTTP client API and protocol implementation, starting
at twisted.web.client.Agent. It's still pretty low-level, but much
more flexible than the old API.
- There were many improvements to the WSGI support.

In Twisted Conch:
- PyASN1 is now used to parse SSH keys (which means you now need to
install it to use Conch).
- SFTP servers (especially on Windows) now behave a lot better.

In Twisted Mail:
- The IMAP server and client protocol implementations had many fixes.
For example, SASL PLAIN credentials now work.

In Twisted Words:
- XMPP clients now support the ANONYMOUS SASL authentication type.
- The IRC protocol implementations had many fixes.

And a lot more.


= What is Twisted? =

>From the web site:

Twisted is an event-driven networking engine written in Python and
licensed under the MIT license.

See the FAQ for commonly asked questions about Twisted.

http://twistedmatrix.com/trac/wiki/FrequentlyAskedQuestions

If you want to get started with Twisted, the first thing you should do
is read the Twisted Core Documentation.

http://twistedmatrix.com/projects/core/documentation/howto/index.html

Twisted projects variously support TCP, UDP, SSL/TLS, multicast, Unix
sockets, a large number of protocols (including HTTP, NNTP, IMAP, SSH,
IRC, FTP, and others), and much more.

Enjoy!

-- 
Christopher Armstrong
http://radix.twistedmatrix.com/
http://planet-if.com/
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Summerfield]

On 2 Dec, 19:28, David H Wild  wrote:
> In article
> <351fcb4c-4e88-41b0-a0aa-b3d63832d...@e23g2000yqd.googlegroups.com>,
>    Mark Summerfield  wrote:
>
> > I only just found out that I was supposed to give a different URL:
> >http://www.informit.com/promotions/promotion.aspx?promo=137519
> > This leads to a web page where you can download the document (just by
> > clicking the "Download Now" button), but if you _choose_ you can also
> > enter your name and email to win some sort of prize.
>
> There is a typographical fault on page 4 of this pdf file. The letter "P"
> is missing from the word "Python" at the head of the comparison columns.

I can't see that problem---I've tried the PDF with evince, gv,
acroread, and okular, and no missing "P" on page 4. I don't have a
machine with RISC OS on it so I can't test on that environment!

> --
> David Wild using RISC OS on broadbandwww.davidhwild.me.uk

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Insane Problem

[Victor Subervi]

Hi;
I have spent 2-3 hours trying to track this bug. Here's the code snippet:

  form = cgi.FieldStorage()
  fn = getattr(options, 'products')
  ourOptionsNames = []
  optionsNames, doNotUse  = fn('names')
  for name in optionsNames:
test = table + '-' + name
print test
check = form.getfirst(test, '')
print check
if check != '':
  ourOptionsNames.append(name)

Now, when it looks through with test=='products', it doesn't report that any
of the values from the form are checked. However, when I explicitly write
out something like:
print form.getfirst('products-sizes', '')
which I checked on the form from the referring page, it does in fact print
out! My test prints show that 'products-sizes' is being passed to "check"
and should therefore be appended to "ourOptionsNames". But it isn't! What am
I missing here??
TIA,
Victor
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Re: How to set object parameters nicely?

[allen.fowler]

> >>> Is there a better way to do this?
> >> class MyOb(object):
> >>      def __init__(self, **kwargs):
> >>          self.__dict__.update(kwargs)
>
> >> ob1 = MyOb(p1="Tom", p3="New York")
> >> ob2 = MyOb(p1="Joe", p2="j...@host", p3="New Jersey")
>
> > I've tried this, but have found two issues:
>
> > 1) I can't set default values.
> > 2) I can't set required values.
>
> > In both of the above cases, if theobjectis created without the
> > "exact" dict() I expect, all the assumption my methods make about what
> > is available in "self" fall apart.
>
> > Perhaps, as Diez mentioned, my approach is wrong.   What would be the
> > right thing to do in this situation?
>
> There is no general answer to this. It depends on your actual problem.
>
> Diez

What are some of the patterns that tend to be used?

-- AF
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[John Bokma]

Mark Summerfield  writes:

> On 1 Dec, 23:52, John Bokma  wrote:
>> Mark Summerfield  writes:
>> > It is available as a free PDF download (no registration or anything)
>> > from InformIT's website. Here's the direct link:
>> >http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/promotions/...
>>
>> Thanks!
>>
>> > And of course, if you want more on Python 3, there's always the
>> > documentation---or my book:-)
>> > "Programming in Python 3 (Second Edition)" ISBN-10: 0321680561.
>>
>> Meh, second edition already? Haven't read the entire first edition
>> yet. Which is IMO a good book (I also gave it to my brother as a
>> present).
>
> If it is any consolation, the second edition should have a much longer
> life, now that we have the language moratorium. (I _really_ wanted to
> cover 3.1.)

Nah, I wasn't really complaining. Moreover, I am glad I didn't finish
the first edition, so I have less of a problem starting in the 2nd
edition from the beginning. From what I've read in the 1st edition it's
an excellent book.

>> Only negative point (to me) so far is that in the beginning (p8-9) the
>> book mentions placing Python programs in C:\py3eg which gives me the
>> unpleasant feeling that someone is coding on Windows XP with
>> Administrator rights...
>
> OK, you got me there,

I knew it ;-) Should've emailed you months ago and maybe it would have
changed in the 2nd edition :-(

> I only use Windows for testing purposes and my
> personal logon account does have Administrator rights, which I assumed
> was standard for personal machines?

I use XP Professional and the first thing I do after installation is
creating a limited user account for my day to day work. As far as I know
this can also be done in XP Home, but I've no experience with home.

> Also, the path is short. It is
> only a suggestion, it really doesn't matter where you unpack the
> examples.

My issue with it is that it somewhat promotes working with Administrator
rights, which is as dangerous as working with root rights on other OSes
if the machine is not connected to the Internet. If it's connected to
the Internet it's way more dangerous, sadly.

Anyway, thanks for writing IMO a very good book, and I *am* happy with a
second edition.

-- 
John Bokma

Read my blog: http://johnbokma.com/
Hire me (Perl/Python): http://castleamber.com/
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[David H Wild]

In article
<351fcb4c-4e88-41b0-a0aa-b3d63832d...@e23g2000yqd.googlegroups.com>,
   Mark Summerfield  wrote:
> I only just found out that I was supposed to give a different URL:
> http://www.informit.com/promotions/promotion.aspx?promo=137519
> This leads to a web page where you can download the document (just by
> clicking the "Download Now" button), but if you _choose_ you can also
> enter your name and email to win some sort of prize.

There is a typographical fault on page 4 of this pdf file. The letter "P"
is missing from the word "Python" at the head of the comparison columns.

-- 
David Wild using RISC OS on broadband
www.davidhwild.me.uk
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Re: Noob thread lock question

[Diez B. Roggisch]

Astley Le Jasper schrieb:

I have a number of threads that write to a database. I have created a
thread lock, but my question is this:

- If one thread hits a lock, do a) all the other threads stop, or b)
just the ones that come to the same lock?


Only the ones coming the the same lock.


- I presume that the answer is b. In which case do the threads stop
only if they come to the same instance of a lock. For example, you
could have a lock instance for one database and another instance for
another database (first_db_thread_lock = threading.RLock() 
second_db_thread_lock = threading.RLock()).



There is nothing like "not an instance of a lock". So it's essentially 
the same question as the first, and thus the answer is also: yes, only 
for the *same* lock, which is an instance.


Diez
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Noob thread lock question

[Astley Le Jasper]

I have a number of threads that write to a database. I have created a
thread lock, but my question is this:

- If one thread hits a lock, do a) all the other threads stop, or b)
just the ones that come to the same lock?
- I presume that the answer is b. In which case do the threads stop
only if they come to the same instance of a lock. For example, you
could have a lock instance for one database and another instance for
another database (first_db_thread_lock = threading.RLock() 
second_db_thread_lock = threading.RLock()).

I appreciate this is a bit of a noob question, but I didn't want to
assume anything.

ALJ
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Re: Coding Cross Correlation Function in Python

[DarthXander]

On Dec 2, 7:12 pm, sturlamolden  wrote:
> For two 1D ndarrays, the cross-correlation is
>
> from numpy.fft import rfft, irfft
> from numpy import fliplr
>
> xcorr = lambda x,y : irfft(rfft(x)*rfft(fliplr(y)))
>
> Normalize as you wish, and preferably pad with zeros before invoking
> xcorr.

Thanks, though I'd like to do this longer hand than the built in
functions! Great to approximate it though.
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Re: Coding Cross Correlation Function in Python

[sturlamolden]

On 2 Des, 18:50, DarthXander  wrote:

> However to do this 700 times seems ridiculous. How would I get python
> to perform this for me for t in a range of roughly 0-700?

For two 1D ndarrays, the cross-correlation is

from numpy.fft import rfft, irfft
from numpy import fliplr

xcorr = lambda x,y : irfft(rfft(x)*rfft(fliplr(y)))

Normalize as you wish, and preferably pad with zeros before invoking
xcorr.





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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Dickinson]

On Dec 2, 4:41 pm, "John Posner"  wrote:
>   Goal: place integer 456 flush-right in a field of width 8
>
>    Py2: "%%%dd" % 8 % 456
>    Py3: "{0:{1}d}".format(456, 8)
>
> With str.format(), you don't need to nest one formatting operation within  
> another. A little less mind-bending, and every little bit helps!

Or even "{:{}d}".format(456, 8), in 3.1 and 2.7 (when it appears).
But you can do this with % formatting, too.  In either 2.x or 3.x:

>>> "%*d" % (8, 456)
' 456'

--
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Carsten Haese]

John Posner wrote:
>  Goal: place integer 456 flush-right in a field of width 8
> 
>   Py2: "%%%dd" % 8 % 456
>   Py3: "{0:{1}d}".format(456, 8)
> 
> With str.format(), you don't need to nest one formatting operation
> within another.

With string interpolation, you don't need to do that, either.
>>> '%*d' % (8,456)
' 456'

--
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http://informixdb.sourceforge.net

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Re: can python do this?

[Anssi Saari]

Rounak  writes:

> I am a complete newbie. I want to know if the following can be done 
> using python or should I learn some other language:
> (Basically, these are applescripts that I wrote while I used Mac OS)
> 1.Web Page Image to Wallpaper:
> A script that takes the current image in a browser and sets it as a
> wallpaper. 
> http://forums.obdev.at/viewtopic.php?f=24&t=3462

I don't know if any Linux web browsers are particularly scriptable. 
Firefox at least is pretty much limited to opening URLs and some other
windows. OTOH, you can do that specific thing by just right clicking
on the image in question and selecting set as desktop background...

> 2.Screenshot with name, format, Dropbox upload and public URL
> I used to run this script,type the name for screenshot and press return.
> The screenshot would be uploaded to Dropbox and public url would be
> copied to clipboard.
> http://forums.obdev.at/viewtopic.php?f=24&t=3448

I think this should be easily doable with Python, at least the
screenshot and clipboard parts. You can write your own Python code or
use it as glue for utils like xwd, convert, xsel, xclip, xmessage...

No idea if there's any way to talk to Dropbox from Python again since
I know nothing about it.

> 3.Play, pause, set rating to track in iTunes (a music player) with
> keyboard shortcuts without activating iTunes. I know there is no iTunes
> for Linux but is there a scriptable player. See hundreds of scripts
> for iTunes here: http://dougscripts.com/

Don't really know again, I've found iTunes handy for managing
podcasts, but that use doesn't need scripting. In Linux, at least
Amarok is scriptable via Javascript. mplayer is generally scriptable
in its slave mode, but it's more a video player than music. mpd is a
music server which even has a Python client to control it (Sonata). 

But really, global hot key mapping is more of a windowing system thing
than a scripting thing. I'm sure you can map your keys to do anything
you want, in whatever environment you use in Linux.
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Coding Cross Correlation Function in Python

[DarthXander]

I have two data sets which I wish to perform the discrete correlation
function on and then plot the results for many values of t to see what
if any time lag exists between the data.
Thus far my code is;

import csv
import pylab
from pylab import *
from numpy import *
from numpy import array

HSBC=csv.reader(open("HSBC data.csv"))
Barclays=csv.reader(open("Barclays data.csv"))

x=[]
a=[]
y=[]
b=[]
g=[]
h=[]
d=[]

for Date, Close in HSBC:
x.append(Date)
a.append(float(Close))

for Date, Close in Barclays:
y.append(Date)
b.append(float(Close))

for index in range(len(a)):
g.append(a[index]-mean(a))

for index in range(len(b)):
h.append(b[index]-mean(b))

r=std(a)
s=std(b)

So I have all the necessary components for the DCF.

However I'm not faced with the challenge of performing the DCF for t
in the range of potentially 0-700 or so.
Currently I could do it individually for each value of tau ie;

t1=[]
for index in range(len(g)-1):
j=(g[index]*h[index+1])/(r*s)
t1.append(j)

d.append(mean(t1))

However to do this 700 times seems ridiculous. How would I get python
to perform this for me for t in a range of roughly 0-700?

Thanks
Alex
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Re: Delaunay triangulation

[sturlamolden]

On 2 Des, 15:28, David Robinow  wrote:
> On Tue, Dec 1, 2009 at 8:31 PM, Vincent Davis  
> wrote:
> > Anyone know of a python implementation of Delaunay triangulation?
>
> Matplotlib has one.
> There's also Delny �...@pypi
>
> It's been several years since I needed this. I can't remember the pros/cons.

There is also a skikit add-on to NumPy/SciPy.

http://scikits.appspot.com/delaunay
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[John Posner]

On Wed, 02 Dec 2009 10:55:23 -0500, Mark Summerfield   
wrote:



On Dec 1, 2:03 pm, Mark Summerfield  wrote:

I've produced a 4 page document that provides a very concise summary
of Python 2<->3 differences plus the most commonly used new Python 3
features. It is aimed at existing Python 2 programmers who want to
start writing Python 3 programs and want to use Python 3 idioms rather
than those from Python 2 where the idioms differ.


Mark, I add my thanks to those of the other responders. If you find space,  
you might consider adding another str.format() feature:


 Goal: place integer 456 flush-right in a field of width 8

  Py2: "%%%dd" % 8 % 456
  Py3: "{0:{1}d}".format(456, 8)

With str.format(), you don't need to nest one formatting operation within  
another. A little less mind-bending, and every little bit helps!


-John
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Re: Python without wrapper script

[Jean-Michel Pichavant]

eric.frederich wrote:

Is there a way to set up environment variables in python itself
without having a wrapper script.

The wrapper script is now something like

#!/bin/bash

export LD_LIBRARY_PATH="/some/thing/lib:$LD_LIBRARY_PATH"
export LD_LIBRARY_PATH="/another/thing/lib:$LD_LIBRARY_PATH"

export PATH="/some/thing/bin:$PATH"
export PATH="/another/thing/bin:$PATH"

python ./someScript.py
  

try in someScript.py

os.environ['PATH'] = "/some/thing/bin:"+ os.environ['PATH']

example:

import subprocess
import os
p = subprocess.Popen('/bin/echo $TEST', shell=True, stdout=subprocess.PIPE )
p.communicate()[0]
> '\n'

os.environ['TEST'] = 'hello'
p = subprocess.Popen('/bin/echo $TEST', shell=True, stdout=subprocess.PIPE )
p.communicate()[0]
> 'hello\n'

JM


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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Summerfield]

On Dec 2, 4:22 pm, Mark Summerfield  wrote:
> On Dec 2, 11:31 am, "Martin P. Hellwig" 
> wrote:
>
> > MarkSummerfieldwrote:
>
> > > It is available as a free PDF download (no registration or anything)
> > > from InformIT's website. Here's the direct link:
> > >http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/promotions/...
>
> > 
> > Very handy! Am I wrong in assuming that you forgot to include that
> > file() is gone in favour of open()?
>
> No you are not wrong in assuming that I forgot that:-(
>
> My lame excuse is that file() was introduced for isinstance() testing
> and similar, and never really as a replacement for open().
>
> Anyway, I have now added:
>
>     fh = file(fname, mode) | fh = open(fname, mode)
>
> I've sent a new PDF with this change to InformIT, so hopefully it'll
> become available soon 
> fromhttp://www.informit.com/promotions/promotion.aspx?promo=13751

Oops wrong URL again, should have been:
http://www.informit.com/promotions/promotion.aspx?promo=137519
... time to go offline and sleep ...
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Summerfield]

On Dec 2, 11:31 am, "Martin P. Hellwig" 
wrote:
> MarkSummerfieldwrote:
>
> > It is available as a free PDF download (no registration or anything)
> > from InformIT's website. Here's the direct link:
> >http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/promotions/...
>
> 
> Very handy! Am I wrong in assuming that you forgot to include that
> file() is gone in favour of open()?

No you are not wrong in assuming that I forgot that:-(

My lame excuse is that file() was introduced for isinstance() testing
and similar, and never really as a replacement for open().

Anyway, I have now added:

fh = file(fname, mode) | fh = open(fname, mode)

I've sent a new PDF with this change to InformIT, so hopefully it'll
become available soon from
http://www.informit.com/promotions/promotion.aspx?promo=13751
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Re: Python without wrapper script

[Ulrich Eckhardt]

eric.frederich wrote:
> Is there a way to set up environment variables in python itself
> without having a wrapper script.

Yes, sure, you can set environment variables...

> The wrapper script is now something like
> 
> #!/bin/bash
> 
> export LD_LIBRARY_PATH="/some/thing/lib:$LD_LIBRARY_PATH"
> export LD_LIBRARY_PATH="/another/thing/lib:$LD_LIBRARY_PATH"
> 
> export PATH="/some/thing/bin:$PATH"
> export PATH="/another/thing/bin:$PATH"
> 
> python ./someScript.py

...but this won't work, I'm afraid.

LD_LIBRARY_PATH is for the program loader / dynamic linker under Linux. This
thing is what is invoked _before_ the program is started, any later
modifications to the environment are ignored.

Similarly PATH, which tells the shell (e.g. bash) where to find executables.
If you need that to e.g. find 'python' itself, you're out of luck.
Otherwise, I believe Python itself doesn't use PATH, so you could set it
inside and any shells started from Python should pick it up.

Uli

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Re: Question about file objects...

[J]

On Wed, Dec 2, 2009 at 09:27, nn  wrote:
>> Is there a way to read the file, one item at a time, delimited by
>> commas WITHOUT having to read all 16,000 items from that one line,
>> then split them out into a list or dictionary??

> File iteration is a convenience since it is the most common case. If
> everything is on one line, you will have to handle record separators
> manually by using the .read() method on the file
> object and searching for the comma. If everything fits in memory the
> straightforward way would be to read the whole file with .read() and
> use .split(",") on the returned string. That should give you a nice
> list of everything.

Agreed. The confusion came because the guy teaching said that
iterating the file is delimited by a carriage return character...
which to me sounds like it's an arbitrary thing that can be changed...

I was already thinking that I'd have to read it in small chunks and
search for the delimiter i want...  and reading the whole file into a
string and then splitting that would would be nice, until the file is
so large that it starts taking up significant amounts of memory.

Anyway, thanks both of you for the explanations... I appreciate the help!

Cheers
Jeff



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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Summerfield]

On Dec 2, 11:20 am, Wolodja Wentland 
wrote:
> On Wed, Dec 02, 2009 at 00:10 -0800, Mark Summerfield wrote:
> > On 1 Dec, 18:30, Lie Ryan  wrote:
> > > Also, I'm not sure what this change is referring to:
> > > Python 2                 Python 3
> > > L = list(seq)            L = sorted(seq)
> > > L.sort()
>
> > > L.sort is still available in python, and sorted() have been available
> > > since python 2. Both list.sort() and sorted() are for different purpose,
> > > and neither will be deprecated. What's the change here?
>
> > The document is about idioms as well as changes. In this case both
> > approaches work in both versions, but it seems that there are still a
> > lot of people who don't know about sorted(), so I put it in to show it
> > as an idiom.
>
> It would be quite nice if you could mark all the Python 3 idioms that
> work in Python 2.X as well. This would allow readers that are still using
> Python 2.X and are used to the 'old way' to adapt their coding style
> accordingly. You could just add a little (2.X) after the idiom for
> example.

Yes it would be nice, but it isn't quite so simple. To take sorted()
as just one example, it was introduced in 2.4 so arguably using it
isn't valid/idiomatic for Python 2.x programs where you care about
backwards compatibility for the Python 2.x series... But my main
reason for not wanting to do this is that the document is aimed at
people who want to write Python 3, not to encourage people to stick
with 2:-)

>
> And thanks for the nice cheat sheet! :-D

Thanks!

> --
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>  : :'  :    
>  `. `'`     4096R/CAF14EFC
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>
>  signature.asc
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Summerfield]

On Dec 2, 8:53 am, Mark Dickinson  wrote:
> On Dec 2, 8:01 am, MarkSummerfield wrote:
>
> > On 1 Dec, 17:50, Mark Dickinson  wrote:
> > > My only quibble is with the statement on the first page that
> > > the 'String % operator is deprecated'.  I'm not sure that's
> > > true, for all values of 'deprecated'.  There don't appear
> > > to be any definite plans for getting rid of it just yet.
>
> > I didn't make this up:-)
>
> No, I didn't imagine for a second that you had!
>
> > According tohttp://docs.python.org/dev/3.0/whatsnew/3.0.html
> > "The plan is to eventually make this the only API for string
> > formatting, and to start deprecating the % operator in Python 3.1."
>
> I think that's a doc bug.  "The plan is to ..." should read: "The plan
> was
> originally to ...".  (Well, at least in the 3.1 version of the
> "what's new in 3.0" documentation;  the 3.0 version that you linked to
> isn't even autogenerated any more, AFAIK, so fixes to the ReST source
> for that file never make it to the web site.)
>
> I'm a little confused myself about what's actually happening with
> % formatting, but here's a fairly recent python-dev posting from
> the BDFL:
>
> http://mail.python.org/pipermail/python-dev/2009-September/092399.html

Well it seems clear to me that the BDFL wants to kill of % formatting,
but wasn't able to for Python 3... So I still think it is reasonable
(1) to describe it as deprecated and (2) to only teach and use
str.format().
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Summerfield]

On Dec 1, 2:03 pm, Mark Summerfield  wrote:
> I've produced a 4 page document that provides a very concise summary
> of Python 2<->3 differences plus the most commonly used new Python 3
> features. It is aimed at existing Python 2 programmers who want to
> start writing Python 3 programs and want to use Python 3 idioms rather
> than those from Python 2 where the idioms differ.
>
> It uses Python 3.1 syntax since that looks like being the standard for
> a few years in view of the language moratorium.
>
> The document is U.S. Letter size but will also print fine on A4
> printers.
>
> It is available as a free PDF download (no registration or anything)
> from InformIT's website. Here's the direct 
> link:http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/promotions/...
>
> And of course, if you want more on Python 3, there's always the
> documentation---or my book:-)
> "Programming in Python 3 (Second Edition)" ISBN-10: 0321680561.


I only just found out that I was supposed to give a different URL:
http://www.informit.com/promotions/promotion.aspx?promo=137519
This leads to a web page where you can download the document (just by
clicking the "Download Now" button), but if you _choose_ you can also
enter your name and email to win some sort of prize.
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Python without wrapper script

[eric.frederich]

Is there a way to set up environment variables in python itself
without having a wrapper script.

The wrapper script is now something like

#!/bin/bash

export LD_LIBRARY_PATH="/some/thing/lib:$LD_LIBRARY_PATH"
export LD_LIBRARY_PATH="/another/thing/lib:$LD_LIBRARY_PATH"

export PATH="/some/thing/bin:$PATH"
export PATH="/another/thing/bin:$PATH"

python ./someScript.py
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Re: can python do this?

[Rounak]

Thanks Allan, I did find PIL in Synaptic Package Manager and installed
it successfully. However, I cannot use it. The reason is:
1. I had installed python3 using sudo apt-get install python3 but python
2 still remains. And it seems Scite (my python editor) is looking for
python 2.

Terminal Output:
$ python -V
Python 2.6.4
$ python3 -V
Python 3.1.1+

Output from Scite:
>python -u "sshot.py"
Traceback (most recent call last):
  File "sshot.py", line 1, in 
import ImageGrab
  File "/usr/lib/python2.6/dist-packages/PIL/ImageGrab.py", line 34, in

import _grabscreen
ImportError: No module named _grabscreen
>Exit code: 1

How to make Scite use python3 where it will hopefully find the just
installed PIL.




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Re: can python do this?

[Bruno Desthuilliers]

Rounak a écrit :
 
http://stackoverflow.com/questions/69645/take-a-screenshot-via-a-python-script-linux



the first solution in this thread requires python imaging library which
I did find here: http://www.pythonware.com/products/pil/faq.htm
But i would like to know if there are easier ways to install this
instead of compiling it from the source.



Depends on your linux distro - but PIL is a fairly stable and widely 
used lib, so I fail to imagine any modern distro not having a packaged 
PIL install (rpm, ebuild, whatever).

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Re: can python do this?

[Diez B. Roggisch]

Rounak wrote:

> 
>>  
>>
http://stackoverflow.com/questions/69645/take-a-screenshot-via-a-python-script-linux
>> 
> the first solution in this thread requires python imaging library which
> I did find here: http://www.pythonware.com/products/pil/faq.htm
> But i would like to know if there are easier ways to install this
> instead of compiling it from the source.

Did you bother checking your distributions package management?

Diez
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Re: can python do this?

[Allan Davis]

Try your distribution of linux package management tool.  You will find PIL
there

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Co-Chair, CajunJUG
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On Wed, Dec 2, 2009 at 9:34 AM, Rounak  wrote:

>
> >
> >
> http://stackoverflow.com/questions/69645/take-a-screenshot-via-a-python-script-linux
> >
> the first solution in this thread requires python imaging library which
> I did find here: http://www.pythonware.com/products/pil/faq.htm
> But i would like to know if there are easier ways to install this
> instead of compiling it from the source.
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: can python do this?

[Grant Edwards]

On 2009-12-02, Rounak  wrote:
>
>> Python can do anything Applescript can do with the appscript module -
>> see . And,
>> naturally, very much more.
>
> wait, sorry, i forgot to mention. I am now on Linux. I want to
> know what python can do in Linux.

Python can do pretty much anything except kernel modules.

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Re: can python do this?

[Rounak]

>  
> http://stackoverflow.com/questions/69645/take-a-screenshot-via-a-python-script-linux
> 
the first solution in this thread requires python imaging library which
I did find here: http://www.pythonware.com/products/pil/faq.htm
But i would like to know if there are easier ways to install this
instead of compiling it from the source.

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Re: can python do this?

[Diez B. Roggisch]

Rounak wrote:

> 
>> Python can do anything Applescript can do with the appscript module -
>> see . And,
>> naturally, very much more.
> 
> wait, sorry, i forgot to mention. I am now on Linux. I want to know what
> python can do in Linux. On Mac, I am glad to use applescript.

This question is not so easy to answer. Because such functionality heavily
depends on your actual desktop environment - KDE, Gnome, or something
entirely different. 

However, I'd say that using python you have a good chance of exploiting the
services that are actually available to you.

For example, taking a screenshot:

 
http://stackoverflow.com/questions/69645/take-a-screenshot-via-a-python-script-linux


Uploading that to dropbox is simple python urllib stuff.

And  there seem to be ways to insert things into the clipboard as well:

  http://arminstraub.com/bits-and-bytes/kde-clipboard-on-the-command-line

Diez
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Re: can python do this?

[Rounak]

> Python can do anything Applescript can do with the appscript module -
> see . And,
> naturally, very much more.

wait, sorry, i forgot to mention. I am now on Linux. I want to know what python 
can do in Linux. On Mac, I am glad to use applescript.


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Re: pbs scripts

[Simon Brunning]

2009/12/2 aoife :
> Hi,very new.hoping to incorporate python into my postgrad.
>
> Basically I have 2,000 files.I want to write a script that says:
>
> open each file in turn

If they are in one directory, look at the glob module. If they are in
a bunch of sub-directories, see os.walk(), or .

For looping through the files, see .

> for each file:
>       open this pbs script and run MUSCLE (a sequence alignment tool)
> on each file

Is MUSCLE a command-line tool? If so, see the subprocess module.

>       close this file

Do you actually need to open the file, or just run a command on it?
Sounds like the latter to me.

>       move on to next file.

Give it a go. Any problems, I'm sure we'd be happy to help.

-- 
Cheers,
Simon B.
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Re: can python do this?

[Diez B. Roggisch]

Rounak wrote:

> I am a complete newbie. I want to know if the following can be done
> using python or should I learn some other language:
> (Basically, these are applescripts that I wrote while I used Mac OS)
> 1.Web Page Image to Wallpaper:
> A script that takes the current image in a browser and sets it as a
> wallpaper.
> http://forums.obdev.at/viewtopic.php?f=24&t=3462
> 
> 2.Screenshot with name, format, Dropbox upload and public URL
> I used to run this script,type the name for screenshot and press return.
> The screenshot would be uploaded to Dropbox and public url would be
> copied to clipboard.
> http://forums.obdev.at/viewtopic.php?f=24&t=3448
> 
> 3.Play, pause, set rating to track in iTunes (a music player) with
> keyboard shortcuts without activating iTunes. I know there is no iTunes
> for Linux but is there a scriptable player. See hundreds of scripts
> for iTunes here: http://dougscripts.com/

As python has an apple-script binding, yes, it's possible, should even be a
rather smooth transition.

Diez
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Re: can python do this?

[Simon Brunning]

2009/12/2 Rounak :
> I am a complete newbie. I want to know if the following can be done
> using python or should I learn some other language:
> (Basically, these are applescripts that I wrote while I used Mac OS)

Python can do anything Applescript can do with the appscript module -
see . And,
naturally, very much more.

I have some driving iTunes examples I'd be happy to send you off-list
if you're interested.

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Re: xmlrpc idea for getting around the GIL

[sturlamolden]

On 2 Des, 02:47, Patrick Stinson 
wrote:

> We don't need extension modules, and all we need to do is run some
> fairly basic scripts that make callbacks and use some sip-wrapped
> types.

Sure, you use SIP but not extension modules...


> - Python is not suitable for real-time work.
>
> Not true. We have been running python callback code using
> PyObject_CallObject from within our audio thread for some time without
> a problem, and it's *extremely* fast.

It seems you are confusing "real-time" with "real-fast". The fact that
something runs fast does not make it "real-time".

Python is not suitable for real-time applications, nor are the OSes
commonly used to run Python.



> We
> need just a ltle push to get our code to work at low latencies,
> and the only thing that is standing in our way is that all threads
> 9usually around 20 have to block on the Gil, and this causes small
> gaps in the sound at low latencies (around 5ms, or 64 sample period).
>
> ...almost perfect.

Python is not programmed with real-time applications in mind: You have
no guarrantees on maximum time-lag when a thread is blocked on the
GIL.

"Priority requests" (i.e. pre-emptive multitasking) was removed from
Antoine's "newgil" branch, but that is the kind of mechanism you would
need. Even with priority requests, Python would not be suitable for
real-time apps, as extension modules (e.g. C++ wrapped with SIP) can
hold the GIL forever.

You will also need an OS with a real-time scheduler and a real-time C
library, such as QNX or VxWorks.

I find thea idea of a true real-time Python very interesting, but it
would take a completely reworked interpreter.






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can python do this?

[Rounak]

I am a complete newbie. I want to know if the following can be done 
using python or should I learn some other language:
(Basically, these are applescripts that I wrote while I used Mac OS)
1.Web Page Image to Wallpaper:
A script that takes the current image in a browser and sets it as a
wallpaper. 
http://forums.obdev.at/viewtopic.php?f=24&t=3462

2.Screenshot with name, format, Dropbox upload and public URL
I used to run this script,type the name for screenshot and press return.
The screenshot would be uploaded to Dropbox and public url would be
copied to clipboard.
http://forums.obdev.at/viewtopic.php?f=24&t=3448

3.Play, pause, set rating to track in iTunes (a music player) with
keyboard shortcuts without activating iTunes. I know there is no iTunes
for Linux but is there a scriptable player. See hundreds of scripts
for iTunes here: http://dougscripts.com/

Thanks.



I am a complete newbie. I want to know if the following can be done 
using python or should I learn some other language:
(Basically, these are applescripts that I wrote while I used Mac OS)
1.Web Page Image to Wallpaper:
A script that takes the current image in a browser and sets it as a
wallpaper. 
http://forums.obdev.at/viewtopic.php?f=24&t=3462

2.Screenshot with name, format, Dropbox upload and public URL
I used to run this script,type the name for screenshot and press return.
The screenshot would be uploaded to Dropbox and public url would be
copied to clipboard.
http://forums.obdev.at/viewtopic.php?f=24&t=3448

3.Play, pause, set rating to track in iTunes (a music player) with
keyboard shortcuts without activating iTunes. I know there is no iTunes
for Linux but is there a scriptable player. See hundreds of scripts
for iTunes here: http://dougscripts.com/

Thanks.






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Re: Delaunay triangulation

[km]

check CGAL (cgal.org)
it has python bindings
Krishna

On Wed, Dec 2, 2009 at 11:28 PM, David Robinow  wrote:

> On Tue, Dec 1, 2009 at 8:31 PM, Vincent Davis 
> wrote:
> > Anyone know of a python implementation of Delaunay triangulation?
>
> Matplotlib has one.
> There's also Delny  @pypi
>
> It's been several years since I needed this. I can't remember the
> pros/cons.
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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pbs scripts

[aoife]

Hi,very new.hoping to incorporate python into my postgrad.

Basically I have 2,000 files.I want to write a script that says:

open each file in turn
for each file:
   open this pbs script and run MUSCLE (a sequence alignment tool)
on each file
   close this file
   move on to next file.

any help would be great.
Aoife
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Re: Question about file objects...

[Andre Engels]

On Wed, Dec 2, 2009 at 3:14 PM, J  wrote:
> Something that came up in class...
>
> when you are pulling data from a file using f.next(), the file is read
> one line at a time.
>
> What was explained to us is that Python iterates the file based on a
> carriage return as the delimiter.
> But what if you have a file that has one line of text, but that one
> line has 16,000 items that are comma delimited?
>
> Is there a way to read the file, one item at a time, delimited by
> commas WITHOUT having to read all 16,000 items from that one line,
> then split them out into a list or dictionary??

If f is a file object, f.read(1) will get the next byte of the file.
Get single-character strings that way until you arrive at a ",", then
concatenate what you have received before that.

-- 
André Engels, andreeng...@gmail.com
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Re: Question about file objects...

[nn]

On Dec 2, 9:14 am, J  wrote:
> Something that came up in class...
>
> when you are pulling data from a file using f.next(), the file is read
> one line at a time.
>
> What was explained to us is that Python iterates the file based on a
> carriage return as the delimiter.
> But what if you have a file that has one line of text, but that one
> line has 16,000 items that are comma delimited?
>
> Is there a way to read the file, one item at a time, delimited by
> commas WITHOUT having to read all 16,000 items from that one line,
> then split them out into a list or dictionary??
>
> Cheers
> Jeff
>
> --
>
> Ogden Nash  - "The trouble with a kitten is that when it grows up,
> it's always a cat." 
> -http://www.brainyquote.com/quotes/authors/o/ogden_nash.html

File iteration is a convenience since it is the most common case. If
everything is on one line, you will have to handle record separators
manually by using the .read() method on the file
object and searching for the comma. If everything fits in memory the
straightforward way would be to read the whole file with .read() and
use .split(",") on the returned string. That should give you a nice
list of everything.
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Re: Delaunay triangulation

[David Robinow]

On Tue, Dec 1, 2009 at 8:31 PM, Vincent Davis  wrote:
> Anyone know of a python implementation of Delaunay triangulation?

Matplotlib has one.
There's also Delny  @pypi

It's been several years since I needed this. I can't remember the pros/cons.
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Question about file objects...

[J]

Something that came up in class...

when you are pulling data from a file using f.next(), the file is read
one line at a time.

What was explained to us is that Python iterates the file based on a
carriage return as the delimiter.
But what if you have a file that has one line of text, but that one
line has 16,000 items that are comma delimited?

Is there a way to read the file, one item at a time, delimited by
commas WITHOUT having to read all 16,000 items from that one line,
then split them out into a list or dictionary??

Cheers
Jeff

-- 

Ogden Nash  - "The trouble with a kitten is that when it grows up,
it's always a cat." -
http://www.brainyquote.com/quotes/authors/o/ogden_nash.html
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Re: Recursion head scratcher

[Joel Madigan]

On 12/2/09, Dave Angel  wrote:
> Joel Madigan wrote:
>> Hi everyone!
>> Sorry this isn't strictly a Python question but my algorithms professor
>> contends that given the standard recursive-backtracking maze solving
>> algorithm:
>>
>> width=6
>> height=4
>> maze=[[1,0,1,1,0,1],
>>   [0,0,1,0,0,0],
>>   [1,0,1,0,1,0],
>>   [0,0,0,0,1,1]]
>> visited = [[False for x in range(width)] for y in range(height)]
>>
>> sx=1
>> sy=2
>> ex=4
>> ey=0
>>
>> def findPath(x,y):
>> if (x < 0 or x >= width or y < 0 or y >= height):
>> return False
>> elif maze[y][x] == 1:
>> return False
>> elif visited[y][x]:
>> return False
>> elif (x == ex and y == ey):
>> print "(%d,%d)"%(x,y),
>> return True
>> else:
>> visited[y][x] = True
>>
>> if findPath(x-1,y) or \
>>findPath(x+1,y) or \
>>findPath(x,y-1) or \
>>findPath(x,y+1):
>> print "(%d,%d)"%(x,y),
>> return True
>> else:
>> return False
>>
>> print findPath(sx,sy)
>>
>> that it is possible to make it print the path to the finish in the order
>> the
>> steps were taken.  That is, the algorithm as written produces:
>> (4,0) (4,1) (3,1) (3,2) (3,3) (2,3) (1,3) (1,2) True
>>
>> Rather than
>> (1,2) (1,3) (2,3) (3,3) (3,2) (3,1) (4,1) (4,0) True
>>
>> Furthermore, he claims it's a "one line change" without using a stack or
>> any
>> other extra data structure.  But I can't figure it out to save my life.
>>  This isn't homework, there isn't credit on the line.  I think he said it
>> just to mess with us.  Can anyone point me in the right direction?  It's
>> driving me crazy.  The output it gives makes perfect sense, since it just
>> prints out each step as the stack unwinds.  Normally you would print the
>> output BEFORE recursing, but in this case you only want to print the step
>> if
>> it is actually part of the path.  And you don't know that until after the
>> recursion.
>>
>> Can anyone shed some light on this?
>>
>> Thanks,
>> Joel
>>
>>
> How about swapping sx,sy with ex,ey ?  That's one line (one statement).
> And the rest of the algorithm appears to be symmetric.  Basically,
> you're reversing time, and starting with the end point, descending till
> you find the start point.
>
> DaveA
>
>
Wow... that's devilishy clever.  I can see  that I still have a long
way to travel on my path.  Thanks for your insight.
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Re: Don't Understand This Error

[Victor Subervi]

To those who caught the colon at the end of what I thought was going to be
def but turned out to be something else, thank.

On Wed, Dec 2, 2009 at 5:55 AM, Bruno Desthuilliers
 wrote:

> On Wed, Dec 2, 2009 at 2:33 AM, Victor Subervi 
>> wrote:
>>
>>>
>>> def colors(callingTable, which='', specificTables=[]):
>>>
>>
> Warning : default arguments are eval'd only once, at function creation
> time. This is a well known gotcha that can lead to unexpected behaviours
> like:
>
>
> def foo(x, bar=[])
>   bar.append("gotcha %s" % x)
>   print bar
>
> for i in range(5):
>   bar(i)
>

Thanks for this instructive example.
V
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Martin P. Hellwig]

Mark Summerfield wrote:


It is available as a free PDF download (no registration or anything)
from InformIT's website. Here's the direct link:
http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/promotions/python/python2python3.pdf


Very handy! Am I wrong in assuming that you forgot to include that 
file() is gone in favour of open()?


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'If consumed, best digested with added seasoning to own preference.'
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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Wolodja Wentland]

On Wed, Dec 02, 2009 at 00:10 -0800, Mark Summerfield wrote:
> On 1 Dec, 18:30, Lie Ryan  wrote:

> > Also, I'm not sure what this change is referring to:
> > Python 2                 Python 3
> > L = list(seq)            L = sorted(seq)
> > L.sort()
> >
> > L.sort is still available in python, and sorted() have been available
> > since python 2. Both list.sort() and sorted() are for different purpose,
> > and neither will be deprecated. What's the change here?
> 
> The document is about idioms as well as changes. In this case both
> approaches work in both versions, but it seems that there are still a
> lot of people who don't know about sorted(), so I put it in to show it
> as an idiom.

It would be quite nice if you could mark all the Python 3 idioms that
work in Python 2.X as well. This would allow readers that are still using
Python 2.X and are used to the 'old way' to adapt their coding style
accordingly. You could just add a little (2.X) after the idiom for
example.

And thanks for the nice cheat sheet! :-D

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Re: Don't Understand This Error

[Bruno Desthuilliers]

On Wed, Dec 2, 2009 at 2:33 AM, Victor Subervi  wrote:


def colors(callingTable, which='', specificTables=[]):


Warning : default arguments are eval'd only once, at function creation 
time. This is a well known gotcha that can lead to unexpected behaviours 
like:



def foo(x, bar=[])
   bar.append("gotcha %s" % x)
   print bar

for i in range(5):
   bar(i)


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Re: Can't print Chinese to HTTP

[Gnarlodious]

On Nov 30, 5:53 am, "Martin v. Löwis" wrote:

> #!/usr/bin/python
> print("Content-type:text/plain;charset=utf-8\n\n")
> sys.stdout.buffer.write('晉\n'.encode("utf-8"))

Does this work for anyone? Because all I get is a blank page. Nothing.
If I can establish what SHOULD work, maybe I can diagnose this
problem.

-- Gnarlie
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Re: Bored.

[Necronymouse]

Thanks for reaction, I will prohably choose some project as you
said...



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Re: xmlrpc idea for getting around the GIL

[alex23]

Patrick Stinson  wrote:
> Not true. We sell the industry leading sampler engine, and it has been
> paying my salary for three years. It's high performance - every cycle
> counts. Our sampled instruments is loaded as a plugin from third-party
> applications and has been used to make movies you have seen. Our
> customers love it and have never complained about problems with the
> scripting engine.

As an occasional bedroom producer I have to ask if you are talking
about EastWest's Play?

When was Python support added? I'm surprised I missed this at the
time...
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Delaunay triangulation

[Vincent Davis]

Anyone know of a python implementation of Delaunay triangulation?

  *Vincent Davis
720-301-3003 *
vinc...@vincentdavis.net
 my blog  |
LinkedIn
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Re: python and vc numbers

[Daniel Dalton]

> Can you make do with the tempfile module? Or you'd need to identify
> from an external process which console is locked?

Perhaps, I wrote a small hack: 
- Manually set environment variable TTYNUMBER in .bash_profile
- Then use this in the script, to establish what tty I'm working with.

Thanks

-- 
Cheers,
Dan

http://members.iinet.net.au/~ddalton/



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Multiprocessing recycle worker if max request reached

[Maris Ruskulis]

Hello!
Currently I'm writing little xmlrpc server, because of one c library 
used there is memory leak, which couldn't be fixed. So I decide to use 
multiprocessing, spawn pool of workers and recycle worker if it reaches 
max request count. I managed to set counter for worker, but I could not 
figure out how to recycle worker if counter reaches some value. Is there 
some well known  solution to solve this? Such functionality seems is not 
part of multiprocessing package.

Thank You!
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Re: Don't Understand This Error

[Chris Rebert]

On Wed, Dec 2, 2009 at 2:33 AM, Victor Subervi  wrote:
> I get the following error:
>
>  /var/www/html/angrynates.com/cart/chooseOptions.py
>     8 from login import login
>     9 import string
>    10 import options
>    11 from particulars import optionsTables, addStore
>    12
> options undefined
>
> SyntaxError: invalid syntax (options.py, line 140)
>   args = ('invalid syntax',
> ('/var/www/html/angrynates.com/cart/options.py', 140, 85, " colorsTables,
> colorsNames = colors('products', 'specificTables', specificTables):\n"))
>   filename = '/var/www/html/angrynates.com/cart/options.py'
>   lineno = 140
>   msg = 'invalid syntax'
>   offset = 85
>   print_file_and_line = None
>   text = " colorsTables, colorsNames = colors('products',
> 'specificTables', specificTables):\n"
>
> I don't understand the 'text = "..." part of the last line.

It's the text of the specific line of code that caused the error, I think.

> Here's the line from the code:
>
>     colorsTables, colorsNames = colors('products', 'specificTables',
> specificTables):

The syntax error is that you have an illegal colon at the end of that
line. Remove that colon.

> No "text". I'm just calling a function and getting the results. Here's the
> pared-down function:
>
> def colors(callingTable, which='', specificTables=[]):

The error lies in the caller of colors().

Cheers,
Chris
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Don't Understand This Error

[Victor Subervi]

I get the following error:

 /var/www/html/angrynates.com/cart/chooseOptions.py
8 from login import login
9 import string
   10 import options
   11 from particulars import optionsTables, addStore
   12
options undefined

SyntaxError: invalid syntax (options.py, line 140)
  args = ('invalid syntax', ('/var/www/html/
angrynates.com/cart/options.py', 140, 85, " colorsTables, colorsNames =
colors('products', 'specificTables', specificTables):\n"))
  filename = '/var/www/html/angrynates.com/cart/options.py'
  lineno = 140
  msg = 'invalid syntax'
  offset = 85
  print_file_and_line = None
  text = " colorsTables, colorsNames = colors('products',
'specificTables', specificTables):\n"

I don't understand the 'text = "..." part of the last line. Here's the line
from the code:

colorsTables, colorsNames = colors('products', 'specificTables',
specificTables):

No "text". I'm just calling a function and getting the results. Here's the
pared-down function:

def colors(callingTable, which='', specificTables=[]):
  code = []
  names = []
  meanings = []
  code.append({'black': 'FF', 'gray': '465945', 'silver': '708090',
'white': '0F4D92', 'maroon': 'B03060', 'red': 'FE2712', 'purple': '50404D',
'fuchsia': 'FF77FF', 'green': '00A550', 'lime': '32CD32', 'olive': '6B8E23',
'yellow': '9ACD32', 'navy blue': 'CC7722', 'blue': '99', 'teal':
'E2725B', 'aqua': '7FFFD4'})
  meanings.append('These are the standard Web colors.')
  names.append('standardWebColors')
  if which == 'specificTables':
whichTablesToReturn = []
i = 0
while i < len(names): # We utilize the name of the table to determine
where it is in the code tuple
  for table in specificTables:
if names[i] == table:
  whichTablesToReturn.append(i)
  i += 1
returnTheseTables = []
for table in whichTablesToReturn:
  returnTheseTables.append(whichTablesToReturn)
returnTheseNames = []
for table in whichTablesToReturn:
  returnTheseNames.append(whichTablesToReturn)
return returnTheseTables, returnTheseNames
  else:
return optionsDict(which)

Please help me understand what this error is trying to show me.
TIA,
Victor
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Re: Recursion head scratcher

[Tim Wintle]

On Wed, 2009-12-02 at 02:07 -0500, Joel Madigan wrote:
> 
> that it is possible to make it print the path to the finish in the
> order the steps were taken.  That is, the algorithm as written
> produces: (4,0) (4,1) (3,1) (3,2) (3,3) (2,3) (1,3) (1,2) True 
> 
> Rather than (1,2) (1,3) (2,3) (3,3) (3,2) (3,1) (4,1) (4,0) True 
> 
> Furthermore, he claims it's a "one line change" without using a stack
> or any other extra data structure

The way I see immediately is a three line change (if you include
modifying/removing the existing print statements). It will be one line
shorter to print the other order.

As a hint - think of what the python interpreter's stack looks like when
it's running your code at the moment - that's the stack you're currently
using (and need to use) to store the results you print.

Tim

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Re: Help in wxpython

[Dave Angel]

madhura vadvalkar wrote:

Hi

I am trying to write an  PAINT like application where on the mouse
click a circle is drawn on canvas. I am new to python and using
wxpython to create this.

here is the code:

import wx

class SketchWindow(wx.Window):

def __init__ (self, parent,ID):

wx.Window.__init__(self, parent, ID)

self.panel =wx.Panel(self, size= (350,350))
self.pen=wx.Pen( 'blue',4)
self.pos=(0,0)
self.InitBuffer()
self.Bind(wx.EVT_LEFT_DOWN,self.OnLeftDown)

def InitBuffer(self):

size=self.GetClientSize()
self.Buffer=wx.EmptyBitmap(size.width,size.height)
dc=wx.BufferedDC(None,self.buffer)
  


You spelled the instance attribute differently.  You initialized it as 
"Buffer" but reference it as "buffer"   Lowercase would be more standard.


I am getting the following error:

Traceback (most recent call last):
  File "C:/Python26/circle.py", line 42, in 
frame=SketchFrame(None)
  File "C:/Python26/circle.py", line 38, in __init__
self.sketch = SketchWindow(self, -1)
  File "C:/Python26/circle.py", line 12, in __init__
self.InitBuffer()
  File "C:/Python26/circle.py", line 19, in InitBuffer
dc=wx.BufferedDC(None,self.buffer)
AttributeError: 'SketchWindow' object has no attribute 'buffer'

Please tell me what I am doing wrong.

Thanks


  

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Re: Recursion head scratcher

[Dave Angel]

Joel Madigan wrote:

Hi everyone!
Sorry this isn't strictly a Python question but my algorithms professor
contends that given the standard recursive-backtracking maze solving
algorithm:

width=6
height=4
maze=[[1,0,1,1,0,1],
  [0,0,1,0,0,0],
  [1,0,1,0,1,0],
  [0,0,0,0,1,1]]
visited = [[False for x in range(width)] for y in range(height)]

sx=1
sy=2
ex=4
ey=0

def findPath(x,y):
if (x < 0 or x >= width or y < 0 or y >= height):
return False
elif maze[y][x] == 1:
return False
elif visited[y][x]:
return False
elif (x == ex and y == ey):
print "(%d,%d)"%(x,y),
return True
else:
visited[y][x] = True

if findPath(x-1,y) or \
   findPath(x+1,y) or \
   findPath(x,y-1) or \
   findPath(x,y+1):
print "(%d,%d)"%(x,y),
return True
else:
return False

print findPath(sx,sy)

that it is possible to make it print the path to the finish in the order the
steps were taken.  That is, the algorithm as written produces:
(4,0) (4,1) (3,1) (3,2) (3,3) (2,3) (1,3) (1,2) True

Rather than
(1,2) (1,3) (2,3) (3,3) (3,2) (3,1) (4,1) (4,0) True

Furthermore, he claims it's a "one line change" without using a stack or any
other extra data structure.  But I can't figure it out to save my life.
 This isn't homework, there isn't credit on the line.  I think he said it
just to mess with us.  Can anyone point me in the right direction?  It's
driving me crazy.  The output it gives makes perfect sense, since it just
prints out each step as the stack unwinds.  Normally you would print the
output BEFORE recursing, but in this case you only want to print the step if
it is actually part of the path.  And you don't know that until after the
recursion.

Can anyone shed some light on this?

Thanks,
Joel

  
How about swapping sx,sy with ex,ey ?  That's one line (one statement).  
And the rest of the algorithm appears to be symmetric.  Basically, 
you're reversing time, and starting with the end point, descending till 
you find the start point.


DaveA

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Re: Moving from Python 2 to Python 3: A 4 page "cheat sheet"

[Mark Dickinson]

On Dec 2, 8:01 am, Mark Summerfield  wrote:
> On 1 Dec, 17:50, Mark Dickinson  wrote:
> > My only quibble is with the statement on the first page that
> > the 'String % operator is deprecated'.  I'm not sure that's
> > true, for all values of 'deprecated'.  There don't appear
> > to be any definite plans for getting rid of it just yet.
>
> I didn't make this up:-)

No, I didn't imagine for a second that you had!

> According to http://docs.python.org/dev/3.0/whatsnew/3.0.html
> "The plan is to eventually make this the only API for string
> formatting, and to start deprecating the % operator in Python 3.1."

I think that's a doc bug.  "The plan is to ..." should read: "The plan
was
originally to ...".  (Well, at least in the 3.1 version of the
"what's new in 3.0" documentation;  the 3.0 version that you linked to
isn't even autogenerated any more, AFAIK, so fixes to the ReST source
for that file never make it to the web site.)

I'm a little confused myself about what's actually happening with
% formatting, but here's a fairly recent python-dev posting from
the BDFL:

http://mail.python.org/pipermail/python-dev/2009-September/092399.html

Mark
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Re: High-performance Python websites

[Bruno Desthuilliers]

Rami Chowdhury a écrit :

On Monday 30 November 2009 10:55:55 inhahe wrote:
On Wed, Nov 25, 2009 at 7:33 PM, ShoqulKutlu  

wrote:

Hi,

Managing load of high volume of visitors is a common issue for all
kind of web technologies. I mean this is not the python issue. This
issue is mostly about server level designs. You need to supply load
balancing for both web servers and databases to make your web site
able to respond to several concurrent visitors. Of course a good
programmed website is a key performance issue but for your mention
I would also suggest considering how many hardwares, how many
webservers, how many database cluster and which database server
should be used or will be used in the future..

I don't know a lot about this issue, but take apache + php.  every
time a page is loaded a new instance of php  is loaded to run the
page, 


AFAIK that's only the case for PHP-CGI, and Python as a CGI scripting 
language is used the same way.


Yeps.

Apache is very often run with mod_php, 
though, which embeds the PHP interpreter; mod_python does something 
similar for Python.


Indeed.

And FWIW, this has very few impact wrt/ load balancing issues.

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Re: getattr problem

[Bruno Desthuilliers]

Victor Subervi wrote:


(NB : answering to the OP - the post didn't show up on clpy)


Hi;
I have the following code that execute without a problem:


Fine. But it fails to execute here - ImportError on the 3rd line 
("options"), NameErrors on the 4th line ("addStore") and 5th line 
("optionTables").



import sys,os
sys.path.append(os.getcwd())
import options
storesTables = []


OT, but the official naming convention in Python is 
all_lower_with_underscores.



junkStores = string.join(addStore(), ', ')


junkStores = ", ".join(addStore())


for table in optionsTables():


OT again, but a general (not python-specific) naming rule is to use 
nouns for variables and verbs for functions. I almost failed to spot the 
parens after "optionsTables". "getOptionsTables" or something like this 
would make your intent more obvious IM(NS)HO.



  if table not in ('particulars', junkStores):


I dont know for sure what junkStores looks like at this point, but given 
the call to string.join, chances are this test doesn't work as expected 
- cf the following snippet:


"""
>>> foo = ("bar", "baaz, back")
>>> "bar" in foo
True
>>> "baaz" in foo
False
>>>
"""


storesTables.append(table)
for table in storesTables:



You don't need two loops here - you could as well proceed as you go, ie:


for table in optionsTables():
   if pass_some_test(table):
   proceed_with(table)



  try:
fn = getattr(options, table)
print fn()
  except:
pass


RRRGHHH ! NO ! DONT ! EVER ! DO ! THAT !

You have to either *properly* handle and exception OR let it propagate. 
For the record, even sys.exit is implemented as an exception.



I need to change the obvious line to this or something similar (that 
actually works):


fn = getattr(options, '%s("names")' % table)

That is, I need to pass the variable "names" to each table as it is 
called.


How does this relate to the above line of code ???

It really looks like you're programming by accident (IOW : try anything 
until it seems to "work", but without any understanding of what your 
code is *really* doing)



How do I do this?


If the question is "how do I pass a variable to a function", then you 
probably didn't write the above code and shouldn't even touch it before 
you learn CS101. Else, please explain more exactly what you're trying to 
do - would be better with an executable, self-contained example.


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Help in wxpython

[madhura vadvalkar]

Hi

I am trying to write an  PAINT like application where on the mouse
click a circle is drawn on canvas. I am new to python and using
wxpython to create this.

here is the code:

import wx

class SketchWindow(wx.Window):

def __init__ (self, parent,ID):

wx.Window.__init__(self, parent, ID)

self.panel =wx.Panel(self, size= (350,350))
self.pen=wx.Pen( 'blue',4)
self.pos=(0,0)
self.InitBuffer()
self.Bind(wx.EVT_LEFT_DOWN,self.OnLeftDown)

def InitBuffer(self):

size=self.GetClientSize()
self.Buffer=wx.EmptyBitmap(size.width,size.height)
dc=wx.BufferedDC(None,self.buffer)
dc.SetBackground(wx.Brush(self.GetBackgroundColour()))
dc.Clear()
self.Drawcircle(dc)
self.reInitBuffer=False

def OnLeftDown(self,event):
self.pos=event.GetPositionTuple()
self.CaptureMouse()

def Drawcircle(self,dc):
pen=wx.Pen(colour,thickness,wx.SOLID)
dc.SetPen(pen)
dc.DrawCircle(self.pos.x,self.pos.y,r)

class SketchFrame(wx.Frame):
def __init__(self, parent):

wx.Frame.__init__(self, parent, -1, "Sketch Frame",size=(800,600))
self.sketch = SketchWindow(self, -1)

if __name__=='__main__':
app=wx.PySimpleApp()
frame=SketchFrame(None)
frame.Show(True)
app.MainLoop()

I am getting the following error:

Traceback (most recent call last):
  File "C:/Python26/circle.py", line 42, in 
frame=SketchFrame(None)
  File "C:/Python26/circle.py", line 38, in __init__
self.sketch = SketchWindow(self, -1)
  File "C:/Python26/circle.py", line 12, in __init__
self.InitBuffer()
  File "C:/Python26/circle.py", line 19, in InitBuffer
dc=wx.BufferedDC(None,self.buffer)
AttributeError: 'SketchWindow' object has no attribute 'buffer'

Please tell me what I am doing wrong.

Thanks









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