[Tutor] [tutor] list order change
You can also sort a list so that is ordered in reverse or alphabetically Cheers, Michael ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] List Changing Order
Steven D'Aprano wrote: Corey Richardson wrote: Tutors, I recall that the keys of dictionaries have arbitrary order, and may change over time. Is this true of lists? I can't find the answer from a simple Google search. Thank you! Only if you re-arrange it yourself. list.sort(), list.reverse() and random.shuffle(list) explicitly change the list's order. You can also manually move items around, e.g.: list[3], list[5] = list[5], list[3] # swap items 3 and 5 but otherwise lists keep their order. Many thanks, everyone who replied. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] If os.path.lexists() isn't working properly
Hello! After all the sugestions I received throught this list; I tried them all and worked ok. At he end I noticed that a single variable change will bring me the results I was looking for. In my code I replaced the line n = os.path.splitext(filename) for: n = os.path.splitext(filepath) p = n[0]+'.prj' if os.path.exists(p): ... code I just wanted to pointed out, thank you all of you! ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] normalize an array
I know this is a simple problem, but I want to do it the most efficient way (that is vectorized...) import numpy as np a = np.array(([1,2,3,4],[1,.2,3,4],[1,22,3,4])) b = np.sum(a,axis=1) for i,elem in enumerate(a): a[i,:] = elem/b[i] suggestions? ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Random Number Question
Dnia 25-11-2010 o 13:20:22 Mac Ryan napisał(a): On Thu, 25 Nov 2010 11:09:10 +0100 Timo wrote: > I was wondering... apart from checking each name individually, is > there any easy-peasy way to get a list of names used in the > standard library (I am thinking to something like "dir()"? This is the webpage I always use for searching an appropriate module: http://docs.python.org/modindex.html I was more thinking to some introspective capacity of python itself rather than a web page... yet, thank you for the link that I did not know beforehand! :) Mac. You can get the list of Python's standard modules by typing help() and then you will see something similar to: help() Welcome to Python 2.6! This is the online help utility. If this is your first time using Python, you should definitely check out the tutorial on the Internet at http://docs.python.org/tutorial/. Enter the name of any module, keyword, or topic to get help on writing Python programs and using Python modules. To quit this help utility and return to the interpreter, just type "quit". To get a list of available modules, keywords, or topics, type "modules", "keywords", or "topics". Each module also comes with a one-line summary of what it does; to list the modules whose summaries contain a given word such as "spam", type "modules spam". help> modules .. .. === The last paragraph of the message shows the answer to you question. HTH, Piotr ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Random Number Question
On Fri, 26 Nov 2010 18:33:07 +0100 Piotr Kamiński wrote: > You can get the list of Python's standard modules by typing help() > and then you will see something similar to: Thanks a lot! This is what I was after! Mac. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Consequences of opening subprocesses?
Hi all, I'm practicing python by rewriting some bash scripts, and I've found a few things that I can't directly translate, like certain calls to command-line tools. I've figured out how to start them with the subprocess module, but I'm wondering if I'm going to get myself in hot water memory- or performance-wise since these scripts are scheduled to run on thousands of files fairly often. Do I need to explicitly close the subprocesses, or clean them up, or something (I have some programming experience, but not a lot of experience with taking into account these kinds of issues - ie, no C ... )? An example is a call to the command-line image manipulation program, ImageMagick: s = subprocess.Popen(['identify', '-format', ''%w %h\n'', 'testimg.jpg'], stdout=subprocess.PIPE) output = s.communicate()[0] print output # output should be the dimensions of testimg.jpg in pixels, ie, 100 50 What I'm thinking is that if, when typed into the terminal, the command appears to give me some output and then exit like the one above (or bash commands like "ls -l"), then I'm ok ... but like I said, I just don't know much about this kind of issue. Can anyone tell me if my intuition's way off on this? Thanks! -Cory ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] normalize an array
John wrote: > I know this is a simple problem, but I want to do it the most > efficient way (that is vectorized...) > > import numpy as np > > a = np.array(([1,2,3,4],[1,.2,3,4],[1,22,3,4])) > b = np.sum(a,axis=1) > > for i,elem in enumerate(a): > a[i,:] = elem/b[i] > suggestions? I'm not a numpy expert, but: (a.transpose()/np.sum(a, axis=1)).transpose() Peter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Consequences of opening subprocesses?
"Cory Teshera-Sterne" wrote I'm wondering if I'm going to get myself in hot water memory- or performance-wise since these scripts are scheduled to run on thousands of files fairly often. It shouldn't be worse than your bash scripts since they implicitly start subprocesses anyway. And if you mare moving some of the functionality into Python it should be better overall. Do I need to explicitly close the subprocesses, or clean them up, or something Mostly they should just close down themselves. Keep a check with a tool like top when testing to ensure you don't get something stuck spinning in a loop, but it should be OK most of the time. An example is a call to the command-line image manipulation program, ImageMagick: s = subprocess.Popen(['identify', '-format', ''%w %h\n'', 'testimg.jpg'], stdout=subprocess.PIPE) If its image manipulation have you checked out the PIL package? It can do most of what imagemagick can do from Python. Its not in the standard library but Google will find it for you. The only snag is that I'm not sure if its on Python 3 yet if you are using v3... # output should be the dimensions of testimg.jpg in pixels, ie, 100 50 PIL should definitely be able to manage that kind of thing. There are also Python bindings to drive ImageMagick from within Python too although I don;t know if they are regularly maintained. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] lambda in python
since in Java i can pass an anonymous class to a function, and this anon class has member functions that can contain a body of implementation codes having the full expression of permissible syntax (if,for,while...), my question is, after seeing various examples of lambda in python being ALL one-liners. These one-liners inside a lambda seems not to have the full permissible use of the full power of python language (if,for,while). Is this correct? Is it correct to say, that within python lambda, you are not allowed to use 'if' ? pls enlighten... ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] lambda in python
john tsolox wrote: since in Java i can pass an anonymous class to a function, and this anon class has member functions that can contain a body of implementation codes having the full expression of permissible syntax (if,for,while...), my question is, after seeing various examples of lambda in python being ALL one-liners. These one-liners inside a lambda seems not to have the full permissible use of the full power of python language (if,for,while). Is this correct? Is it correct to say, that within python lambda, you are not allowed to use 'if' ? pls enlighten... Python lambda is syntactic sugar for an anonymous function, not a class. Lambda is also limited to only a single expression. However, you can use the ternary if: lambda x: x+1 if x < 0 else x-3 is almost the same as: def func(x): if x < 0: return x+1 else: return x-3 -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] %T as a strftime format identifier
Was %T ever a valid format specifier for time.strftime in Python?
I just installed a Python streaming MP3 server called Edna
(http://edna.sourceforge.net/). It was an easy install except that I got
a ValueError on one line, essentially for:
time.strftime("%a, %d %b %Y %T GMT")
After a few seconds experimentation, I found that "%T" is not recognized,
but that in ANSI C strftime, it's a shorthand for %H:%M:%S. I changed it
to:
time.strftime("%a, %d %b %Y %H:%M:%S PST")
and it worked fine.
My question: was %T ever a valid format specifier in Python? My best
guess is that it was when Edna was written (the most current release is
from 2006, and the docs say it needs at least Python 1.5.2, which gives
you an example of its age). It seems odd that the format identifier would
be dropped if it had existed, though; that seems like a needless
upward compatibility issue.
I got this working, so this is mere curiosity; anyone know?
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