Re: Py3K idea: why not drop the colon?
On 2006-11-16, Steve Holden [EMAIL PROTECTED] wrote: I'm always surprised by the amount of energy that's put into this type of discussion - even the OP has suggested that this isn't a big issue. If it's not a big issue why is this thread still going? Every language has a syntax. Why not just accept it as a given and get on with more productive activities? That's all very well if the language has a compromised and ad-hoc syntax. But since Python has a nice clean syntax, it makes me want to be associated with it by investing in its discussions. ;-) -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: remove a list from a list
On 2006-11-17, Rares Vernica [EMAIL PROTECTED] wrote:
Sorry for not being clear from the beginning and for not using
clear variable names.
Problem context:
import os
dirs_exclude = set(('a', 'b', 'e'))
for root, dirs, files in os.walk('python/Lib/email'):
# Task:
# delete from dirs the directory names from dirs_exclude
# case-insensitive
The solution so far is:
for i in xrange(len(dirs), 0, -1):
if dirs[i-1].lower() in dirs_exclude:
del dirs[i-1]
I am looking for a nicer solution.
I'd probably just skip over those dirs as I came them instead of
troubling about mutating the list. Unless the list is needed in
more than one place.
--
Neil Cerutti
--
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Re: trouble writing results to files
On 2006-11-29, Roberto Bonvallet [EMAIL PROTECTED] wrote: BTW, iterating over range(len(a)) is an anti-pattern in Python. Unless you're modifying elements of a, surely? -- Neil Cerutti You can't give him that cutback lane. He's so fast, and he sees it so well. He can also run away from you if he gets a little bit of crack. --Dick Lebeau -- http://mail.python.org/mailman/listinfo/python-list
Re: How to detect what type a variable is?
On 2006-11-29, Grant Edwards [EMAIL PROTECTED] wrote: On 2006-11-29, Leandro Ardissone [EMAIL PROTECTED] wrote: I want to know what type is a variable. For example, I get the contents of an xml but some content is a list or a string, and I need to know what type it is. x = 'asdf' type(x) type 'str' i = 0 type(i) type 'int' That makes me wonder how he manages to store Python objects in xml. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: trouble writing results to files
On 2006-11-29, Roberto Bonvallet [EMAIL PROTECTED] wrote: Neil Cerutti wrote: On 2006-11-29, Roberto Bonvallet [EMAIL PROTECTED] wrote: BTW, iterating over range(len(a)) is an anti-pattern in Python. Unless you're modifying elements of a, surely? enumerate is your friend :) for n, item in enumerate(a): if f(item): a[n] = whatever I was going to bring it up but I had a brainfart about the order of (n, item) in the tuple and was too lazy to look it up. ;-) -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Trying to understand rfc822.Message() behaviour
On 2006-11-30, Phoe6 [EMAIL PROTECTED] wrote:
Hi all,
Have a look at this snippet, I have a file direct.txt and I want to
read it as rfc8222.Message() so that I get the Subject: and Mood: as
Dict Keys and content separately, but I am unable to get the Content
Properly.
fhandle = open('direct.txt','r')
print fhandle.read()
Subject: testing - fortune
Mood: happy
Why should we subsidize intellectual curiosity?
- Ronald Reagan
fhandle.seek(0)
import rfc822
message = rfc822.Message(fhandle)
print message
Subject: testing - fortune
Mood: happy
What is happening here. Why is the message not coming up?
From the Python Documentation 12.11.1 Message Objects:
class Message( file[, seekable])
A Message instance is instantiated with an input object as
parameter. Message relies only on the input object having a
readline() method; in particular, ordinary file objects
qualify. Instantiation reads headers from the input object up
to a delimiter line (normally a blank line) and stores them
in the instance. The message body, following the headers, is
not consumed.
--
Neil Cerutti
We dispense with accuracy --sign at New York drug store
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Re: Automatic increment
On 2006-11-30, Thomas Ploch [EMAIL PROTECTED] wrote: Gheorghe Postelnicu schrieb: Hi, I have a situation of the following type: for line in lineList: for item in line.split() myArray[counter, itemCounter] itemCounter = itemCounter + 1 counter = counter +1 Is there a way to get rid of the manual incrementation of the 2 counters? Thanks, for counter in xrange(len(lineList)): for itemCounter in xrange(len(lineList[counter].split())) myArray[counter, itemCounter] I was going to suggest replacing the whole loop with nothing as the best way of removing the manual counters. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there an easier way to express this list slicing?
On 2006-11-30, John Henry [EMAIL PROTECTED] wrote: If I have a list of say, 10 elements and I need to slice it into irregular size list, I would have to create a bunch of temporary variables and then regroup them afterwords, like: # Just for illustration. Alist can be any existing 10 element list a_list=(,)*10 (a,b,c1,c2,c3,d1,d2,d3,d4,d5)=a_list alist=(a,) blist=(b,) clist=(c1,c2,c3) dlist=(d2,d3,d4,d5) That obviously work but do I *really* have to do that? Please post actual code we can run, rather than text that is almost, but not quite, entirely unlike Python code. BTW: I know you can do: alist=a_list[0] blist=a_list[1] Note that alist and blist are not necessarily lists, as you did not use slice notation. clist=a_list[2:5] dlist=a_list[5:] but I don't see that it's any better. I think it looks much better, personally. If you are iterating through that sequence of slices a lot, consider using a generator that yields the sequence. def parts(items): ... yield items[0:1] ... yield items[1:2] ... yield items[2:5] ... yield items[5:] for seq in parts(range(10)): ... print seq [0] [1] [2, 3, 4] [5, 6, 7, 8, 9] -- Neil Cerutti I guess there are some operas I can tolerate and Italian isn't one of them. --Music Lit Essay -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there an easier way to express this list slicing?
On 2006-11-30, Neil Cerutti [EMAIL PROTECTED] wrote: On 2006-11-30, John Henry [EMAIL PROTECTED] wrote: If I have a list of say, 10 elements and I need to slice it into irregular size list, I would have to create a bunch of temporary variables and then regroup them afterwords, like: # Just for illustration. Alist can be any existing 10 element list a_list=(,)*10 (a,b,c1,c2,c3,d1,d2,d3,d4,d5)=a_list alist=(a,) blist=(b,) clist=(c1,c2,c3) dlist=(d2,d3,d4,d5) That obviously work but do I *really* have to do that? Please post actual code we can run, rather than text that is almost, but not quite, entirely unlike Python code. Ummm... that comment is withdrawn. :-O -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Detecting recursion loops
On 2006-12-01, robert [EMAIL PROTECTED] wrote: Ben Finney wrote: robert [EMAIL PROTECTED] writes: Carl Banks wrote: 2. Consider whether you're unwittingly trying to cover up a bug. ISTM no matter how problematic the input is, you should at least be able to make progress on it. Are you getting this error because, say, you're not incrementing a counter somewhere, and thus recalling a function with the same arguments again? the bug comes in from the I/O input. If a program doesn't gracefully deal with bad input, that's a bug in the program. You should be designing your input handler so that it will do something helpful (even if that's to stop immediately with an informative error message) in the event of bad input, rather than allowing that bad data to send your program into an endless loop. Yet that detection is what the asked alg should do. Example: When a HTML-(content)-relaying sends you around in a circle through a complex handler chain. Being in a cycle doesn't actually prove your program will never halt for that particular input, does it? -- Neil Cerutti Customers who consider our waitresses uncivil ought to see the manager --sign at New York restaurant -- http://mail.python.org/mailman/listinfo/python-list
Re: converting dict to object
On 2006-12-02, Michel Claveau [EMAIL PROTECTED] wrote:
Hi!
Yes.
But...
Try:d = {'a': 1, 'b': 2, 'def': 123}
Ok, I go out...
How to convert a list of strings into a list of integers:
a = ['82', '4', '16']
ai = [int(i) for i in a]
Yes.
But...
Try: a = ['82', '4', '16', 'foo']
Ok, I go out...
--
Neil Cerutti
--
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Re: converting dict to object
On 2006-12-02, John Machin [EMAIL PROTECTED] wrote:
Neil Cerutti wrote:
On 2006-12-02, Michel Claveau [EMAIL PROTECTED] wrote:
Hi!
Yes.
But...
Try:d = {'a': 1, 'b': 2, 'def': 123}
Ok, I go out...
How to convert a list of strings into a list of integers:
a = ['82', '4', '16']
ai = [int(i) for i in a]
Yes.
But...
Try: a = ['82', '4', '16', 'foo']
Ok, I go out...
Michel was making (part of) a valid point: dictionaries have
more flexibility in choice of keys than objects have in
attribute names. More completely:
Suppose d.keys() produces [one, def, foo bar, 3, 3]
o.one is OK.
I made the assumption that Michael was also the original poster,
and had somehow laid a clever trap. If I was wrong about that, my
apologies. It's one thing to ask how to convert 'a' and 'b' to
attributes, but quite another to convert arbitrary text.
The OP might consider adding code to the __init__ method to
check for cases where the dictionary key is not a string
containing a valid Python identifier (not a keyword).
That raises the interesting question of what to do in that case.
Just letting an error occur might be perfectly good behavior.
Plus, I didn't know about...
Observation: the keyword module's iskeyword() function gives an
easy check. If one is supporting multiple versions of Python, a
more complicated (overkill?) approach might be desirable: use
the latest version of Python to generate a source file
containing the latest keywords from keyword.kwlist.
Thanks for the pointer to keyword module. I hadn't noticed it
yet.
--
Neil Cerutti
--
http://mail.python.org/mailman/listinfo/python-list
Re: text adventure question
On 2006-12-02, Ara Kooser [EMAIL PROTECTED] wrote: I am working on a text adventure game for python to get back into python programming. My version 0.1 used only functions so I could get familiar with how those work. I want to move beyond that. I am not sure what would be a good Python way of handling this. I was wondering if classes would help? What things should be included in the main program? The language used by the Infocom implementors was called ZIL, and it so happens that the ZIL manual is available for download. It was sort of a wimpy version of Lisp. http://www.mv.com/ipusers/xlisper/zil.pdf Anyway, the ZIL manual explains how Infocom's library for text adventures worked. That should be inspirational for your design. It's also an entertaining historical artifact, if the history of computer games is your thing. Here's an amusing sampling: EXERCISE THREE Design and implement a full-size game. Submit it to testing, fix all resulting bugs, help marketing design a package, ship the game, and sell at lest 250,000 units. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Execution time of lines within a function
On 2006-12-04, monkeyboy [EMAIL PROTECTED] wrote: I have a function that hotshot says is very slow. I can get the aggregate execution time, but is there a way to get the execution time of each line so I can find the bottleneck? Try 'print_callees' on the stats object for your bottleneck. That may help. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Execution time of lines within a function
On 2006-12-04, monkeyboy [EMAIL PROTECTED] wrote: Thanks Neil, I looked at that, but maybe I don't understand the output. I was hoping to see the cummulative time for the function and then the time associated with each statement (line) within the function. Any suggestions? I don't think the Python Profiler goes down to that level. The next step might be to analyze the function yourself and try to understand why it is so slow. Post the code here and let the readers pick it apart. In the hotshot output below, I can see the function being called 100 times, which is correct, but the rest seems at too low a level for me to understand which statements are causing the slow execution. hw6r3.py:276(main) hw6r3.py:73(findw)(100) 26700.865 Is this the print_callees output? -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Am I stupid or is 'assert' broken in Python 2.5??
On 2006-12-07, Gabriel Genellina [EMAIL PROTECTED] wrote: Yeah, it hit me seconds after I had posted my message. =0 Why didn't I think of it during the 30 minutes I spent banging my head against the keyboard going nuts over this 'bug' ... The same reason you can sometimes find what's wrong just by explaining the symptoms to another guy... Having to put things sorted and simple to understand by another, just makes you think clearly on the problem... I read a story (was it by Brian Kernighan?) the they required programmers to tell their problem to a stuffed animal first before bothering another programmer who might be in the middle of something. The stuffed animal often provided all the assistance that was needed. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Why not just show the out-of-range index?
On 2006-12-07, Tim Chase [EMAIL PROTECTED] wrote: - because error messages are not debugging tools (better use unit Then what are they? Machine-generated poetry? me.__cmp__(gruntbuggly['freddled'].micturations, bee[LURGID].gabbleblotchits[PLURDLED]) == 0 Traceback (most recent call last): File stdin, line 1, in ? VogonPoetryException: Bleem miserable venchit! Bleem forever mestinglish asunder frapt! You should warn people before posting something that dangerous. I would at least have had time to pull the babelfish out of my ear, and so I could have avoided the nosebleed. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
[Followup-To: header set to comp.lang.python.] On 2006-12-08, Mark Tarver [EMAIL PROTECTED] wrote: I'm looking at Python and I see that the syntax would appeal to a newbie. Its clearer than ML which is a mess syntactically. And if you stew it like applesauce, it tastes more like prunes than rhubarb does. But I don't see where the action is in Python. Not yet anyway. Lisp syntax is easy to learn. And giving up an order of magnitude is a high price to pay for using it over Lisp. I find it easier to learn syntax than special forms. But either system comes naturally enough with practice. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Snake references just as ok as Monty Python jokes/references in python community? :)
On 2006-12-08, Roy Smith [EMAIL PROTECTED] wrote: In article [EMAIL PROTECTED], [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I'm semi-seriously wondering if snake jokes are valid in the Python community since technically, Python came from Monty Python, not slithery animals. Problem is I don't know that anyone born after Elvis died gets any of these Monty Python jokes. Is it kosher to make snake jokes/references even though officially they don't have anything to do with the name of our favorite language? (*Everyone* gets snake jokes! :) It's people like you wot cause unrest! I think the decent people of this newsgroup are sick and tired of being told that the decent people of this newsgroup are sick and tired. I'm certainly not! And I'm sick and tired of being told that I am. -- Neil Cerutti Sermon Outline: I. Delineate your fear II. Disown your fear III. Displace your rear --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-09, Bill Atkins [EMAIL PROTECTED] wrote: I'm afraid you're on the wrong track. Any programmer can pick up Lisp and be productive in it these days. Please don't try to make Lisp seem more mysterious or elitist than it really is. It's just a programming language, and anyone can learn it: http://www.gigamonkeys.com/book I got stuck (last year) in that book: http://www.gigamonkeys.com/book/practical-a-portable-pathname-library.html The author didn't do Common Lisp (or me) any favors by drawing my attention to the pathname library. I suppose I missed whatever the point was supposed to be in the midst of the mind-boggling. I meant to get back to it but haven't yet. -- Neil Cerutti We will sell gasoline to anyone in a glass container. --sign at Santa Fe gas station -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-12, André Thieme [EMAIL PROTECTED] wrote: Contrast the much more common a[i] = b[n] with (setf (aref a i) (aref b n)) and the attractions of Python may make more sense. Here Python and Lisp are equal, 7 tokens vs 7 tokens, but in Python one has to write less since [] are 2 chars while aref are 4, plus the setf. But from counting the brain units which I regard as an important factor they are both equal. A comparison of brain units of the above snippets is irrelevant, since the snippets are not equivalent. The Python snippet will work for any object a that provides __setitem__ and any object b that provides __getitem__. I don't know what an equivalent Lisp snippet would be (or even exactly how close the above snippet comes to matching the Python code), but whatever it is would be a better foundation for comparing brain units with the above Python. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-13, hit_the_lights [EMAIL PROTECTED] wrote: Neil Cerutti schrieb: a[i] = b[n] with (setf (aref a i) (aref b n)) and the attractions of Python may make more sense. Here Python and Lisp are equal, 7 tokens vs 7 tokens, but in Python one has to write less since [] are 2 chars while aref are 4, plus the setf. But from counting the brain units which I regard as an important factor they are both equal. A comparison of brain units of the above snippets is irrelevant, since the snippets are not equivalent. The Python snippet will work for any object a that provides __setitem__ and any object b that provides __getitem__. I don't know what an equivalent Lisp snippet would be (or even exactly how close the above snippet comes to matching the Python code), but whatever it is would be a better foundation for comparing brain units with the above Python. It would be exactly like the example given, just aref replaced with something else. An example implementation: == (defgeneric $ (container key)) (defgeneric (setf $) (value container key)) ;;; Implementation for arrays (defmethod $ ((container array) (key integer)) (aref container key)) (defmethod (setf $) (value (container array) (key integer)) (setf (aref container key) value)) == And usage: == CL-USER(3): (defparameter a (vector 1 2 3 4 5)) A CL-USER(4): ($ a 0) 1 CL-USER(5): (setf ($ a 0) 9) 9 CL-USER(6): a #(9 2 3 4 5) == The nice thing is, that you *can* dispatch on the container, the key and the value. That's cool. Thanks for posting the code. Is the above 'duck-typing' idiom considered very useful to a Lisper? It seems logical to me that duck-typing works best in an environment where it is ubiquitous. If users have to implement accessors specifically to use your library, it is not as good as if they had already implemented one as a matter of routine. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-13, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Try reading again. In Lisp, you use () and *your editor* automatically indents according to the universal standard, or you leave it sloppy until other folks reading your code convince you to get a proper programming editor. Indentation does not get out of sync with semantics because the editor virtually never misses parentheses that the Lisp compiler sees. Expressions keep the same meaning even if you have to start breaking them across lines, etc. Yes, it's the same way in Python. Of course, not everything is an expression in Python, so it's not saying quite as much. In Python, you group in your mind, and press indentation keys to make it happen in your editor. The editor cannot help that much, because it cannot read your mind. White space screwups in copy-paste cannot be fixed by the editor automatically, because it cannot read the original programmer's mind, and you have to fix it manually, and risk screwing it up. It is very easy a manual process, possibly as simple as selecting the correct s-expr and pasting it into the right place in your code. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Conditional iteration
On 2006-12-13, Roberto Bonvallet [EMAIL PROTECTED] wrote: at wrote: More pythonic in view would be: for x in [-2, -1, 0, 1, 2, 3, 4] if x 0: ... more code ... Pythonic? Do you realize that Python hasn't even adopted well-known statements like 'switch' and 'do while' because they would be redundant? This could be more convenient to you, but certainly not pythonic. Cheers, I tried it once myself. It seemed like a feasible thing that might work in Python. It didn't annoy me that it didn't work, but it did seem natural to me given the syntax of comprehensions. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-14, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Neil Cerutti wrote: On 2006-12-13, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Expressions keep the same meaning even if you have to start breaking them across lines, etc. Yes, it's the same way in Python. Of course, not everything is an expression in Python, so it's not saying quite as much. I fail to see how it is the same in Python. if self.flee == (foo.humble(pie) / 500 * hats + hippity.hoppity) The indentation of the second line of that expression is entirely irrelevant to Python. The parenthesis I added means I don't have to use the new-line escape character (\), either. In Python, you group in your mind, and press indentation keys to make it happen in your editor. The editor cannot help that much, because it cannot read your mind. White space screwups in copy-paste cannot be fixed by the editor automatically, because it cannot read the original programmer's mind, and you have to fix it manually, and risk screwing it up. It is very easy a manual process, possibly as simple as selecting the correct s-expr and pasting it into the right place in your code. How does a manual correction process come out as simple as don't bother fixing the indentation if you don't care.? This is exactly the questionable math that I was questioning in the original post. Python simply replaces one manual process (moving to the correct scope (usually sitting on an open or close parenthesis) and then hitting the grab-s-expr command) with another (after pasting, correct the indentation--generally a trivial task). I think it's a major stretch to call either process anything but trivially easy for an experiences user of the language. -- Neil Cerutti The Pastor would appreciate it if the ladies of the congregation would lend him their electric girdles for the pancake breakfast next Sunday morning. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-14, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Neil Cerutti wrote: On 2006-12-14, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Neil Cerutti wrote: On 2006-12-13, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Expressions keep the same meaning even if you have to start breaking them across lines, etc. Yes, it's the same way in Python. Of course, not everything is an expression in Python, so it's not saying quite as much. I fail to see how it is the same in Python. if self.flee == (foo.humble(pie) / 500 * hats + hippity.hoppity) The indentation of the second line of that expression is entirely irrelevant to Python. The parenthesis I added means I don't have to use the new-line escape character (\), either. Is this so unconscious that you don't recognize you are doing it, even though you take a sentence to explain what you had to do to work around it? Adding parentheses, new-line escape characters---all this is a burden specific to Python. It already indicated that you are right about Python identation *outside* of an expression, which is where most indentation takes place in Python. But you were wrong that it is meaningful inside an expression. The reformatting (admittedly generally trivial, although again your qualifier of generally undermines your point) process is extra in Python. Period. 1) Recognizing where your code begins and ends to begin the copy-paste process is not unique to either. Equal. Reflecting on what you've written, I see you are right about this issue. Thanks for the correction. 5) After you are done, Pythonistas admit there is a possible step called manually correct the indentation. Meaningful indentation has drawbacks *and* advantages, though. This is pointless discussion if you guys can't even see what you are saying when you write it in your own posts. Please don't assume I speak for all Python programmers. They might be rolling there eyes at me just as much as you are. ;-) -- Neil Cerutti In my prime I could have handled Michael Jordan. Of course, he would be only 12 years old. --Jerry Sloan -- http://mail.python.org/mailman/listinfo/python-list
Re: Routine for prefixing '' before every line of a string
On 2006-12-14, Roberto Bonvallet [EMAIL PROTECTED] wrote: Sanjay wrote: Is somewhere a routine useful to convert a string to lines of maxsize, each prefixed with a ''. This is a typical requirement for 'keeping existing text while replying to a post in a forum'. Take a look to the textwrap module: http://docs.python.org/lib/module-textwrap.html Here is an example: # the text is actually a very long line text = '''Lorem ipsum dolor sit amet, consectetuer adipiscing [...]''' prefix = '' import textwrap lines = [%s %s % (prefix, line) for line in textwrap.wrap(text, width=75)] The solution will need to be instrumented in case of text that is already quotes to one level. All in all, I recommend using Vim's gq command or Emacs' autofill mode, which arlready do the right thing. -- Neil Cerutti The Rev. Merriwether spoke briefly, much to the delight of the audience. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple.index()
On 2006-12-14, Nick Maclaren [EMAIL PROTECTED] wrote: In article [EMAIL PROTECTED], Glenn Hutchings [EMAIL PROTECTED] writes: | | I remain baffled. I accept the explanations, but what I am now | confused by is the reason for the explanations | | Maybe this archive posting, straight from the horse's mouth, will clear | things up once and for all... | | http://www.python.org/search/hypermail/python-1992/0285.html Wonderful! Thanks. Yes, that does. It makes perfect sense. I did say that I thought it would be a rarely used feature :-) Though the full rationale no longer applies to strings, which now have plenty of methods. -- Neil Cerutti Weight Watchers will meet at 7 p.m. Please use large double door at the side entrance. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: WHAT is [0] in subprocess.Popen(blah).communicate()[0]
On 2006-12-14, Fredrik Lundh [EMAIL PROTECTED] wrote: johnny wrote: Can someone tell me what is the reason [0] appears after .communicate() For example: last_line=subprocess.Popen([rtail,-n 1, x.txt], stdout=subprocess.PIPE).communicate()[0] as explained in the documentation, communication() returns two values, as a tuple. [0] is used to pick only the first one. see the Python tutorial for more on indexing and slicing. I like using pattern matching in these simple cases: last_line, _ = subprocess.Popen([rtail,-n 1, x.txt], stdout=subprocess.PIPE).communicate() -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: merits of Lisp vs Python
On 2006-12-15, André Thieme [EMAIL PROTECTED] wrote: In Lisp it is like an IF and represents exactly what we think. IF in Lisp: (if expr (then-part) (else-part)) nif in Lisp: (nif expr (positive-part) (zero-part) (negative-part)) It looks as if it were a construct directly built into Lisp. If one wants one could even add some additional syntax, so that it looks like: (nif expr positive: (foo1) (foo2) zero: (foo3) negative: (foo4)) If you regard that idea nonsense then I suggest you to not use Rubys if-statement anymore. But instead program your own version RubyIF so that in future you have to pass all code inside blocks to your RubyIF function. If you *really* think that the Lisp savings are not worth it, then you would begin with my suggestion today. I don't know how to build a house. It doesn't make me want to live in a cave. ;-) -- Neil Cerutti The third verse of Blessed Assurance will be sung without musical accomplishment. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: array, a better shell
On 2006-12-20, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: For array.array B means unsigned char, and such arrays accept to be initialized from (str) strings too, this is quite useful: from array import array a = array(B, hello) But it seems such capability isn't shared with the append: a.extend(hello) Traceback (most recent call last): File stdin, line 1, in module TypeError: an integer is required Try: a.fromstring(hello) -- Neil Cerutti I have opinions of my own -- strong opinions -- but I don't always agree with them. --George W. Bush -- http://mail.python.org/mailman/listinfo/python-list
Re: DOS, UNIX and tabs
On 2007-01-02, Peter Decker [EMAIL PROTECTED] wrote: On 1/1/07, Tom Plunket [EMAIL PROTECTED] wrote: Maybe I'm also weird, but I use a variable-pitch font when programming in Python. So a tab equals some number of spaces really isn't useful to me. My setup is, tab equals this much space. A year ago I would have thought you were weird, but after reading a post by Ed Leafe, one of the creators of Dabo about using proportional fonts for readability, I thought I'd try it out, thinking that it was pretty wacky. Turns out that after a very brief adjustment period, I liked it! I've been using proportional fonts ever since, and have found only one drawback: code that is indented with spaces looks butt-ugly. I'm glad I switched to tabs for my code. I first came accross it in Stroustrup's _The C++ Programming Language_. I liked the look and the idea immediately, but my editor of choice (by historical accident) Vim, doesn't yet support it. -- Neil Cerutti I've had a wonderful evening, but this wasn't it. --Groucho Marx -- http://mail.python.org/mailman/listinfo/python-list
Re: array of class / code optimization
On 2007-01-03, Jussi Salmela [EMAIL PROTECTED] wrote:
hg kirjoitti:
mm wrote:
Yes, it was the (), equivalent to thiks like new() create new object
from class xy.
s1.append(Word)
s1.append(Word())
But I was looking for a struct equivalent like in c/c++.
And/or union. I can't find it.
Maybe you know a source (URL) Python for c/c++ programmers or things
like that.
Yes, I konw whats an object is...
A struct in C is unrelated to a struct in C++ as a struct in C++ _is_ a
class.
hg
What does your sentence mean, exactly? If I take a C file xyz.c
containing a struct definition S, say, rename it to be xyz.cpp
and feed it to a C++ compiler, the S sure remains a struct and
the C++ compiler has no difficulty in handling it as a struct,
so ?!?
That's true.
But it's also true that
struct foo {
int x, y;
};
is exactly equivalent to:
class foo {
public:
int x, y;
};
The only difference between struct and class in C++ is the
default access specification of its members.
--
Neil Cerutti
For those of you who have children and don't know it, we have a nursery
downstairs. --Church Bulletin Blooper
--
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Re: Sorting on multiple values, some ascending, some descending
On 2007-01-03, dwelden [EMAIL PROTECTED] wrote:
I have successfully used the sort lambda construct described in
http://mail.python.org/pipermail/python-list/2006-April/377443.html.
However, how do I take it one step further such that some
values can be sorted ascending and others descending? Easy
enough if the sort values are numeric (just negate the value),
but what about text?
Is the only option to define an external sorting function to
loop through the list and perform the comparisons one value at
a time?
Another trick is to factor the key application out of the sort.
This may be a good idea if when you want to minimize the number
of times your key function is called.
The idea is to mangle the list temporarily so you can use an
unkeyed sort, and then unmangle the sorted data. Here's a silly
example using a phone directory that's not stored in a format
that's easy to sort.
a = [(Neil Cerutti, 8025552954), (Ted Smith, 8025552281), (Barny
Fife, 8025551105)]
b = [( .join(reversed(x.split())), y) for (x, y) in a]
b
[('Cerutti Neil', '8025552954'), ('Smith Ted', '8025552281'), ('Fife Barny',
'8025551105')]
b.sort()
b
[('Cerutti Neil', '8025552954'), ('Fife Barny', '8025551105'), ('Smith Ted',
'8025552281')]
a = [( .join(reversed(x.split())), y) for (x, y) in b]
a
[('Neil Cerutti', '8025552954'), ('Barny Fife', '8025551105'), ('Ted Smith',
'8025552281')]
--
Neil Cerutti
Eddie Robinson is about one word: winning and losing. --Eddie Robinson's agent
Paul Collier
--
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Re: Sorting on multiple values, some ascending, some descending
On 2007-01-04, Peter Otten [EMAIL PROTECTED] wrote: Neil Cerutti wrote: Another trick is to factor the key application out of the sort. This may be a good idea if when you want to minimize the number of times your key function is called. The idea is to mangle the list temporarily so you can use an unkeyed sort, and then unmangle the sorted data. Here's a silly example using a phone directory that's not stored in a format that's easy to sort. No need to jump through these hoops; list.sort(key=keyfunc) calls keyfunc() exactly once per list item: from random import shuffle items = range(-5, 10) shuffle(items) count = 0 def key(value): ... global count ... count += 1 ... return abs(value) ... items.sort(key=key) count 15 Thanks for the correction! That's very useful information. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Why less emphasis on private data?
On 2007-01-08, Paul Rubin http wrote: Dennis Lee Bieber [EMAIL PROTECTED] writes: I'd be quite concerned about the design environment rather than the immediate code... Probably need something ugly like... from mod1 import B as B1 from mod2 import B as B2 class A(B1, B2): Interesting. I just tried that. mod1.py contains: class B: def foo(self): self.__x = 'mod1' mod2.py contains: class B: def bar(self): self.__x = 'mod2' And the test is: from mod1 import B as B1 from mod2 import B as B2 class A(B1, B2): pass a = A() a.foo() print a._B__x a.bar() print a._B__x Sure enough, mod2 messes up mod1's private variable. When faced with this situation, is there any way to proceed besides using composition instead? -- Neil Cerutti We've got to pause and ask ourselves: How much clean air do we really need? --Lee Iacocca -- http://mail.python.org/mailman/listinfo/python-list
Re: recursive function
On 2007-01-08, cesco [EMAIL PROTECTED] wrote:
Hi,
I have a dictionary of lists of tuples like in the following example:
dict = {1: [(3, 4), (5, 8)],
2: [(5, 4), (21, 3), (19, 2)],
3: [(16, 1), (0, 2), (1, 2), (3, 4)]]
In this case I have three lists inside the dict but this number
is known only at runtime. I have to write a function that
considers all the possible combinations of tuples belonging to
the different lists and return a list of tuples of tuples for
which the sum of the first element of the most inner tuple is
equal to N.
For example, assuming N = 24, in this case it should return:
[((3, 4), (5, 4), (16, 1)), ((3, 4), (21, 3), (0, 2)), ((5, 8), (19,
2), (0, 2))]
What do you mean by most inner tuple?
A simple list comprehension would be enough if only I knew the
number of keys/lists beforehand
len(dict.keys()).
--
Neil Cerutti
Next Sunday Mrs. Vinson will be soloist for the morning service. The pastor
will then speak on It's a Terrible Experience. --Church Bulletin Blooper
--
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Re: Why less emphasis on private data?
On 2007-01-08, hg [EMAIL PROTECTED] wrote:
sturlamolden wrote:
The designers of Java, C++, C#, Ada95, Delphi, etc. seem to think that
if an object's 'internal' variables or states cannot be kept private,
programmers get an irresistible temptation to mess with them in
malicious ways. But if you are that stupid, should you be programming
in any language? The most widely used language is still C, and there is
no concept of private data in C either, nor is it needed.
void test(void)
{
static int i;
}
Do you agree that i is private to test ?
In C one uses the pointer to opaque struct idiom to hide data.
For example, the standard FILE pointer.
--
Neil Cerutti
--
http://mail.python.org/mailman/listinfo/python-list
Re: Why less emphasis on private data?
On 2007-01-08, Jussi Salmela [EMAIL PROTECTED] wrote: Neil Cerutti kirjoitti: In C one uses the pointer to opaque struct idiom to hide data. For example, the standard FILE pointer. To Neil Cerutti: If a programmer in C has got a pointer to some piece of memory, that piece is at the mercy of the programmer. There's no data hiding at all in this case. That's somewhat disingenuous. You get just as much data hiding with an opaque data type in C as you get in C++ or Java. -- Neil Cerutti Potluck supper: prayer and medication to follow. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: Colons, indentation and reformatting.
On 2007-01-09, Leif K-Brooks [EMAIL PROTECTED] wrote: Paddy wrote: Thinking about it a little, it seems that a colon followed by non-indented code that has just been pasted in could also be used by a Python-aware editor as a flag to re-indent the pasted code. How would it reindent this code? if foo: print Foo! if bar: print Bar! Like this? if foo: print Foo! if bar: print Bar! Or like this? if foo: print Foo! if bar: print Bar! That's the key issue. The colon gives the editor an easy clue where a block starts, but the there's no simply way to determine where the block is supposed to end. -- Neil Cerutti Remember in prayer the many who are sick of our church and community. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: Determine an object is a subclass of another
On 2007-01-09, abcd [EMAIL PROTECTED] wrote: How can tell if an object is a subclass of something else? Imagine... class Thing: pass class Animal: pass class Dog: pass d = Dog() I want to find out that 'd' is a Dog, Animal and Thing. Such as... d is a Dog d is a Animal d is a Thing isinstance(d, Dog) isinstance(d, Animal) isinstance(d, Thing) Note that in your example d is not an instance of anything but Dog. If you want a hierarchy, you must say so. Python doesn't even try to make educated guesses. class Thing: pass class Animal(Thing): pass class Dog(Animal): pass -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
A simple lexer
I'm a royal n00b to writing translators, but you have to start
someplace.
In my Python project, I've decided that writing the dispatch code
to sit between the Glulx virtual machine and the Glk API will be
best done automatically, using the handy prototypes.
Below is the prototype of the lexer, and I'd like some comments
in case I'm doing something silly already.
My particular concern are:
The loop checks for each possible lexeme one at a time, and has
rather lame error checking.
I made regexes for matching a couple of really trivial cases for
the sake of consistency. In general, is there a better way to use
re module for lexing.
Ultimately, I'm going to need to build up an AST from the lines,
and use that to generate Python code to dispatch Glk functions. I
realize I'm throwing away the id of the lexeme right now;
suggestions on the best way to store that information are
welcome.
I do know of and have experimented with PyParsing, but for now I
want to use the standard modules. After I understand what I'm
doing, I think a PyParsing solution will be easy to write.
import re
def match(regex, proto, ix, lexed_line):
m = regex.match(proto, ix)
if m:
lexed_line.append(m.group())
ix = m.end()
return ix
def parse(proto):
Return a lexed version of the prototype string. See the
Glk specification, 0.7.0, section 11.1.4
parse('0:')
['0', ':']
parse('1:Cu')
['1', ':', 'Cu']
parse('2Qb:Cn')
['2', '', 'Qb', ':', 'Cn']
parse('4Iu#![2SF]+Iu:Is')
['4', 'Iu', '#!', '[', '2', 'S', 'F', ']', '+', 'Iu', ':', 'Is']
arg_count = re.compile('\d+')
qualifier = re.compile('[][+#!]*')
type_name = re.compile('I[us]|C[nus]|[SUF]|Q[a-z]')
o_bracket = re.compile('\\[')
c_bracket = re.compile('\\]')
colon = re.compile(':')
ix = 0
lexed_line = []
m = lambda regex, ix: match(regex, proto, ix, lexed_line)
while ix len(proto):
old = ix
ix = m(arg_count, ix)
ix = m(qualifier, ix)
ix = m(type_name, ix)
ix = m(o_bracket, ix)
ix = m(c_bracket, ix)
ix = m(colon, ix)
if ix == old:
print Parse error at %s of %s % (proto[ix:], proto)
ix = len(proto)
return lexed_line
if __name__ == __main__:
import doctest
doctest.testmod()
--
Neil Cerutti
We dispense with accuracy --sign at New York drug store
--
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An iterator with look-ahead
For use in a hand-coded parser I wrote the following simple iterator with look-ahead. I haven't thought too deeply about what peek ought to return when the iterator is exhausted. Suggestions are respectfully requested. As it is, you can't be sure what a peek() = None signifies until the next iteration unless you don't expect None in your sequence. Using itertools.tee is the alternative I thought about, but caveates in the documentation disuaded me. class LookAheadIter(object): An iterator with the a peek() method, so you can see what's coming next. If there is no look-ahead, peek() returns None. nums = [1, 2, 3, 4, 5] look = LookAheadIter(nums) for a in look: ...print (a, look.peek()) (1, 2) (2, 3) (3, 4) (4, 5) (5, None) def __init__(self, data): self.iter = iter(data) self.look = self.iter.next() self.exhausted = False def __iter__(self): return self def peek(self): if self.exhausted: return None else: return self.look def next(self): item = self.look try: self.look = self.iter.next() except StopIteration: if self.exhausted: raise else: self.exhausted = True return item -- Neil Cerutti We've got to pause and ask ourselves: How much clean air do we really need? --Lee Iacocca -- http://mail.python.org/mailman/listinfo/python-list
Working with named groups in re module
A found some clues on lexing using the re module in Python in an
article by Martin L÷wis.
http://www.python.org/community/sigs/retired/parser-sig/towards-standard/
He writes:
[...]
A scanner based on regular expressions is usually implemented
as an alternative of all token definitions. For XPath, a
fragment of this expressions looks like this:
(?PNumber\\d+(\\.\\d*)?|\\.\\d+)|
(?PVariableReference\\$ + QName + )|
(?PNCName+NCName+)|
(?PQName+QName+)|
(?PLPAREN\\()|
Here, each alternative in the regular expression defines a
named group. Scanning proceeds in the following steps:
1. Given the complete input, match the regular expression
with the beginning of the input.
2. Find out which alternative matched.
[...]
Item 2 is where I get stuck. There doesn't seem to be an obvious
way to do it, which I understand is a bad thing in Python.
Whatever source code went with the article originally is not
linked from the above page, so I don't know what Martin did.
Here's what I came up with (with a trivial example regex):
import re
r = re.compile('(?Pxx+)|(?Paa+)')
m = r.match('aaxaxx')
if m:
for k in r.groupindex:
if m.group(k):
# Find the token type.
token = (k, m.group())
I wish I could do something obvious instead, like m.name().
--
Neil Cerutti
After finding no qualified candidates for the position of principal, the
school board is pleased to announce the appointment of David Steele to the
post. --Philip Streifer
--
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Re: An iterator with look-ahead
On 2007-01-10, Fredrik Lundh [EMAIL PROTECTED] wrote: if you're doing simple parsing on an iterable, it's easier and more efficient to pass around the current token and the iterator's next method: http://online.effbot.org/2005_11_01_archive.htm#simple-parser-1 Thank you. Much better. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Working with named groups in re module
On 2007-01-10, Fredrik Lundh [EMAIL PROTECTED] wrote:
Neil Cerutti wrote:
A found some clues on lexing using the re module in Python in
an article by Martin L÷wis.
Here, each alternative in the regular expression defines a
named group. Scanning proceeds in the following steps:
1. Given the complete input, match the regular expression
with the beginning of the input.
2. Find out which alternative matched.
you can use lastgroup, or lastindex:
http://effbot.org/zone/xml-scanner.htm
there's also a hidden ready-made scanner class inside the SRE
module that works pretty well for simple cases; see:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/457664
Thanks for the excellent pointers.
I got tripped up:
m = re.match('(a+(b*)a+)', 'aaa')
dir(m)
['__copy__', '__deepcopy__', 'end', 'expand', 'group', 'groupdict', 'groups',
'span', 'start']
There are some notable omissions there. That's not much of an
excuse for my not understanding the handy docs, but I guess it
can can function as a warning against relying on the interactive
help.
I'd seen the lastgroup definition in the documentation, but I
realize it was exactly what I needed. I didn't think carefully
enough about what last matched capturing group actually meant,
given my regex. I don't think I saw name there either. ;-)
lastgroup
The name of the last matched capturing group, or None if the
group didn't have a name, or if no group was matched at all.
--
Neil Cerutti
We dispense with accuracy --sign at New York drug store
--
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Re: Need startup suggestions for writing a MSA viewer GUI in python
On 2007-01-10, hg [EMAIL PROTECTED] wrote: Joel Hedlund wrote: Thanks for taking the time! /Joel Hedlund I do not know if PyGtk and PyQT have demos, but wxPython does and includes PyPlot: an easy way to look at the basic features. PyQT does come with an impressive plethora of demos. -- Neil Cerutti The concert held in Fellowship Hall was a great success. Special thanks are due to the minister's daughter, who labored the whole evening at the piano, which as usual fell upon her. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: An iterator with look-ahead
On 2007-01-10, Steven Bethard [EMAIL PROTECTED] wrote: Neil Cerutti wrote: For use in a hand-coded parser I wrote the following simple iterator with look-ahead. There's a recipe for this: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/304373 Note that the recipe efficiently supports an arbitrary look-ahead, not just a single item. I haven't thought too deeply about what peek ought to return when the iterator is exhausted. Suggestions are respectfully requested. In the recipe, StopIteration is still raised on a peek() operation that tries to look past the end of the iterator. That was all I could think of as an alternative, but that makes it fairly inconvenient to use. I guess another idea might be to allow user to provide a no peek return value in the constructor, if they so wish. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Print message with Colors
On 2007-01-11, Laurent Pointal [EMAIL PROTECTED] wrote: prk a écrit : Hi Folks, Is there any procesure for print messages with colors. Yes, see: http://www.google.fr/search?q=python+print+color http://groups.google.fr/groups?as_q=python+print+colornum=100as_ugroup=comp.lang.python See also ANSI escape sequences for the more general subject of color printing on terminals. If you're using Windows NT, 2000, or XP don't bother reading about ANSI escape sequences. They will not work at all with Python on those platforms, even if you use the crummy old COMMAND.COM. I believe it's because Python on those platforms in a console application, which on NT, 2000 and XP doesn't support ANSI escape sequences. It makes IPython's appearance less cool. :-( Try http://effbot.org/downloads/#console for color output that works. -- Neil Cerutti We're going to be exciting. Of course, it was exciting when the Titanic went down. --Bob Weiss -- http://mail.python.org/mailman/listinfo/python-list
Re: Type casting a base class to a derived one?
On 2007-01-11, Frederic Rentsch [EMAIL PROTECTED] wrote: If I derive a class from another one because I need a few extra features, is there a way to promote the base class to the derived one without having to make copies of all attributes? class Derived (Base): def __init__ (self, base_object): # ( copy all attributes ) ... This looks expensive. Moreover __init__ () may not be available if it needs to to something else. Thanks for suggestions How does it make sense to cast a base to a derived in your application? -- Neil Cerutti I'm traveling to all 51 states to see who can stop 85. --Chad Johnson -- http://mail.python.org/mailman/listinfo/python-list
Re: __init__ vs __new__
On 2007-01-11, Daniel Klein [EMAIL PROTECTED] wrote: I've have a program that is using both of the methods below (in different classes of course) for initializing the class. The example below shows a class with the 2 methods with one commented out. class JsubroutineParameters(list): Represents a list of arguments for external subroutine calls. # We only need to override methods which add objects to the list. def __init__(self, alist = []): for objekt in alist: _validateParameter(objekt) self.extend(alist) #def __new__(cls, alist = []): #for objekt in alist: _validateParameter(objekt) #return list.__new__(cls, alist) I don't really notice any behavioral difference. Is there in fact any difference in using one over the other? Performance? Side effects? ??? I am using Python version 2.5. The second version doesn't work the way you might be assuming. Guido's paper says that mutable builtins like list have a dummy __new__ static method. So 'return list.__new__(cls, alist)' does nothing. It seems to work because the base class __init__ performs the initialization (assuming your __init__ above is commented out). You can see this by providing a dummy __init__. class Example(list): def __new__(cls, alist): return list.__new__(cls, alist) def __init__(self, alist): pass a = Example(range(5)) a [] There is no need to use __new__ for mutable builtin types. Since all you want from this construction is a side-effect, you can nevertheless use it in this case. Your __init__ should call the base-class __init__. It's usually a bad idea to provide mutable types as default arguments. Since you aren't modifying alist in __init__ you can get away with it here, but getting in the habit of using the below idiom might save you from a gotcha someday. class JsubroutineParameters(list): def __init__(self, alist=None): if alist is None: alist = [] for objekt in alist: _validateParameter(objekt) list.__init__(self, alist) You will no longer need to call append. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: What happened to SPE?
On 2007-01-11, Paulo Pinto [EMAIL PROTECTED] wrote: does anyone know what happened to SPE? It seems that the address http://pythonide.stani.be is no longer valid. :( SPE lost its web host, and last I heard is looking for a new home. For now you can get it here: http://sourceforge.net/projects/spe/ -- Neil Cerutti We don't necessarily discriminate. We simply exclude certain types of people. --Colonel Gerald Wellman -- http://mail.python.org/mailman/listinfo/python-list
Re: Fixed keys() mapping
On 2007-01-11, George Sakkis [EMAIL PROTECTED] wrote:
I wrote an 'fkdict' dict-like class for mappings with a fixed
set of keys but I'm wondering if there's a simpler way to go
about it.
First off, the main motivation for it is to save memory in case
of many dicts with the same keys, for example when reading from
a csv.DictReader or constructing dicts out of rows fetched from
a database. For example, test_mem(dict) takes up around 246 MB
according to the Windows task manager while test_mem(fkdict)
takes around 49 MB:
It occurs to me you could create custom classes using __slots__
to get something similar. It's not terribly convenient.
class XYDict(object):
__slots__ = ['x', 'y']
def __getitem__(self, item):
return self.__getattribute__(item)
def __setitem__(self, key, item):
return self.__setattr__(key, item)
This isn't terribly convenient because you have to create a new
class for every new set of keys. It isn't obvious to me how to
program a metaclass to automate the process. A lot more
boilerplate is necessary to act like a dict.
def test_mem(maptype):
d = [(i,str(i)) for i in range(1000)]
ds = [maptype(d) for i in xrange(1)]
raw_input('finished')
An additional benefit is predictable ordering (e.g.
fkdict.fromkeys('abcd').keys() == list('abcd')), like several
ordered-dict recipes.
The implementation I came up with goes like this: each fkdict
instance stores only the values as a list in self._values. The
keys and the mapping of keys to indices are stored in a
dynamically generated subclass of fkdict, so that self._keys
and self._key2index are also accessible from the instance. The
dynamically generated subclasses are cached so that the second
time an fkdict with the same keys is created, the cached class
is called.
Since the keys are determined in fkdict.__init__(), this scheme
requires changing self.__class__ to the dynamically generated
subclass. As much as I appreciate Python's dynamic nature, I am
not particularly comfortable with objects that change their
class and the implications this may have in the future (e.g.
how well does this play with inheritance). Is this a valid use
case for type-changing behavior or is there a better, more
mainstream OO design pattern for this ? I can post the
relevant code if necessary.
Since the type gets changed before __init__ finishes, I don't see
any problem with it. It sounds cool.
--
Neil Cerutti
It isn't pollution that is hurting the environment; it's the impurities in our
air and water that are doing it. --Dan Quayle
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Re: passing a variable to an external program
On 2007-01-11, Rich [EMAIL PROTECTED] wrote:
I want to run an external program using os.system() but I want to
include a variable in the middle of the command line.
An example of the type of thing I want to be able to do:
pathname = os.path.dirname(sys.argv[0])
os.system('cscript /nologo ' + pathname + '\test.vbs')
Use / instead of \, or \\ instead of \.
--
Neil Cerutti
Ushers will eat latecomers. --Church Bulletin Blooper
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Re: Matching Directory Names and Grouping Them
On 2007-01-11, J [EMAIL PROTECTED] wrote: Steve- Thanks for the reply. I think what I'm trying to say by similar is pattern matching. Essentially, walking through a directory tree starting at a specified root folder, and returning a list of all folders that matches a pattern, in this case, a folder name containing a four digit number representing year and a subdirectory name containing a two digit number representing a month. The matches are grouped together and written into a text file. I hope this helps. Here's a solution using itertools.groupby, just because this is the first programming problem I've seen that seemed to call for it. Hooray! from itertools import groupby def print_by_date(dirs): r Group a directory list according to date codes. data = [ ... root/Input2/2002/03/, ... root/Input1/2001/01/, ... root/Input3/2005/05/, ... root/Input3/2001/01/, ... root/Input1/2002/03/, ... root/Input3/2005/12/, ... root/Input2/2001/01/, ... root/Input3/2002/03/, ... root/Input2/2005/05/, ... root/Input1/2005/12/] print_by_date(data) root/Input1/2001/01/ root/Input2/2001/01/ root/Input3/2001/01/ BLANKLINE root/Input1/2002/03/ root/Input2/2002/03/ root/Input3/2002/03/ BLANKLINE root/Input2/2005/05/ root/Input3/2005/05/ BLANKLINE root/Input1/2005/12/ root/Input3/2005/12/ BLANKLINE def date_key(path): return path[-7:] groups = [list(g) for _,g in groupby(sorted(dirs, key=date_key), date_key)] for g in groups: print '\n'.join(path for path in sorted(g)) print if __name__ == __main__: import doctest doctest.testmod() I really wanted nested join calls for the output, to suppress that trailing blank line, but I kept getting confused and couldn't sort it out. It would better to use the os.path module, but I couldn't find the function in there lets me pull out path tails. I didn't filter out stuff that didn't match the date path convention you used. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Boilerplate in rich comparison methods
On 2007-01-13, Steven D'Aprano [EMAIL PROTECTED] wrote: On Sat, 13 Jan 2007 10:04:17 -0600, Paul McGuire wrote: [snip] Surely this is only worth doing if the comparison is expensive? Testing beats intuition, so let's find out... class Compare: def __init__(self, x): self.x = x def __eq__(self, other): return self.x == other.x class CompareWithIdentity: def __init__(self, x): self.x = x def __eq__(self, other): return self is other or self.x == other.x Here's the timing results without the identity test: import timeit x = Compare(1); y = Compare(1) timeit.Timer(x = x, from __main__ import x,y).repeat() [0.20771503448486328, 0.16396403312683105, 0.16507196426391602] timeit.Timer(x = y, from __main__ import x,y).repeat() [0.20918107032775879, 0.16187810897827148, 0.16351795196533203] And with the identity test: x = CompareWithIdentity(1); y = CompareWithIdentity(1) timeit.Timer(x = x, from __main__ import x,y).repeat() [0.20761799812316895, 0.16907095909118652, 0.16420602798461914] timeit.Timer(x = y, from __main__ import x,y).repeat() [0.2090909481048584, 0.1968839168548584, 0.16479206085205078] Anyone want to argue that this is a worthwhile optimization? :) Perhaps. But first test it with ==. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Anyone has a nice view_var procedure ?
On 2007-01-15, Gabriel Genellina [EMAIL PROTECTED] wrote:
At Monday 15/1/2007 17:45, Stef Mientki wrote:
Is there some handy/ nice manner to view the properties of some variable ?
As a newbie, I often want to see want all the properties of a var,
and also some corner values (large arrays) etc.
You can try dir(x), vars(x). If you want a nice print, see
the pprint module.
py import csv
py x = csv.DictReader('') # a bogus object
py x
csv.DictReader instance at 0x00BC79B8
py dir(x)
['__doc__', '__init__', '__iter__', '__module__', 'fieldnames',
'next', 'reader'
, 'restkey', 'restval']
py vars(x)
{'restkey': None, 'restval': None, 'fieldnames': None, 'reader':
_csv.reader ob
ject at 0x00BC98B8}
py from pprint import pprint
py pprint(vars(x))
{'fieldnames': None,
'reader': _csv.reader object at 0x00BC98B8,
'restkey': None,
'restval': None}
py
It's an unfortunately limited sort of introspection. To rehash a
recent experience:
import re
import pprint
r = re.match((x+)|(y+), xxx)
pprint.pprint(dir(r))
['__copy__',
'__deepcopy__',
'end',
'expand',
'group',
'groupdict',
'groups',
'span',
'start']
r.lastindex
1
The documentation is deliberately vague:
dir( [object])
[...] The list is not necessarily
complete. If the object is a module object, the list contains
the names of the module's attributes. If the object is a type
or class object, the list contains the names of its attributes,
and recursively of the attributes of its bases. Otherwise, the
list contains the object's attributes' names, the names of its
class's attributes, and recursively of the attributes of its
class's base classes. The resulting list is sorted
alphabetically. [...]
It's unclear to me what attributes an object could have that
aren't included in the above list.
Note: Because dir() is supplied primarily as a convenience for
use at an interactive prompt, it tries to supply an interesting
set of names more than it tries to supply a rigorously or
consistently defined set of names, and its detailed behavior
may change across releases.
In other words, dir is just for fun, like monkey bars. ;)
--
Neil Cerutti
The eighth-graders will be presenting Shakespeare's Hamlet in the church
basement on Friday at 7 p.m. The congregation is invited to attend this
tragedy. --Church Bulletin Blooper
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Re: whats wrong with my reg expression ?
On 2007-01-15, Gert Cuykens [EMAIL PROTECTED] wrote:
thx
PS i also cant figure out what is wrong here ?
rex=re.compile('^(?Pvalue[^]*)$',re.M)
for v in l:
v=rex.match(v).group('value')
v=v.replace('','')
return(l)
v=rex.match(v).group('value')
AttributeError: 'NoneType' object has no attribute 'group'
When the regex doesn't match, match returns None.
--
Neil Cerutti
Strangely, in slow motion replay, the ball seemed to hang in the air for even
longer. --David Acfield
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Re: assert versus print [was Re: The curious behavior of integer objects]
On 2007-01-16, Ron Adam [EMAIL PROTECTED] wrote: I have to admit that part of why assert seems wrong to me is the meaning of the word implies something you shouldn't be able to ignore. While warnings seem like something that can be disregarded. Experienced C coders expect assert to behave like that. The only reason (I know of) to turn off error checking is to optimize. However, removing tests won't usually make a big enough speed difference to be worth the burthen of testing two different versions of the same source code. So to me the assert statement is either dubious syntax-sugar or dangerous, depending on Python's command line arguments. The warning module would seem to have limited applications. Searching my Python distribution shows that it's used for deprecation alerts, and elsewhere for turning those selfsame alerts off. How copacetic! It is the null module. ;-) -- Neil Cerutti Facts are stupid things. --Ronald Reagan -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions question
On 2007-01-16, Victor Polukcht [EMAIL PROTECTED] wrote:
Actually, i'm trying to get the values of first field (Global) , fourth
(200, 4), and fifth (100%) and sixth (100%).
Everything except fourth is simple.
g = Global etsi3 * 4 ok 30 100% 100% Outgoing
import re
r = re.search('\*\s+(\d+)', g)
r.group()
'* 4'
r.group(1)
'4'
--
Neil Cerutti
We're not afraid of challenges. It's like we always say: If you want to go out
in the rain, be prepared to get burned. --Brazillian soccer player
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Re: Regular expressions question
On 2007-01-16, Victor Polukcht [EMAIL PROTECTED] wrote:
On Jan 16, 5:40 pm, Neil Cerutti [EMAIL PROTECTED] wrote:
On 2007-01-16, Victor Polukcht [EMAIL PROTECTED] wrote:
Actually, i'm trying to get the values of first field (Global) , fourth
(200, 4), and fifth (100%) and sixth (100%).
Everything except fourth is simple.
g = Global etsi3 * 4 ok 30 100% 100% Outgoing
import re
r = re.search('\*\s+(\d+)', g)
r.group()
'* 4'
r.group(1)'4'
The same regular expression should work for another string (with *200).
Sorry about that. It should have been:
r = re.search('\*\s*(\d+)', g)
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Re: A note on heapq module
On 2007-01-16, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Scott David Daniels: I'd suggest some changes. It is nice to have Heaps with equal contents equal no matter what order the inserts have been done. Consider how you want Heap([1, 2, 3]) and Heap([3, 1, 2]) to behave. Similarly, it is nice to have str and repr produce canonical representations (I would skip the __str__ code, myself, though). Also, subclasses should get their identities tweaked as so: My version was a *raw* one, just an idea, this is a bit better: http://rafb.net/p/nLPPjo35.html I like your changes. In the beginning I didn't want to put __eq__ __ne__ methods at all, because they are too much slow, but being them O(n ln n) I think your solution is acceptable. Some methods may have a name different from the heap functions: def smallest(self): def push(self, item): def pop(self): def replace(self, item): Two things left I can see: I think the __init__ may have a boolean inplace parameter to avoid copying the given list, so this class is about as fast as the original heapify function (but maybe such thing is too much dirty for a Python stdlib): One more idea, cribbed from the linked list thread elsewhere: it might be nice if your Heap could optionally use an underlying collections.deque instead of a list. I don't know how excellent Python's deque is, but it's possible a deque would provide a faster heap than a contiguous array. C++'s std::deque is the default implementation of C++'s std::priority_queue for that reason (unless I'm confused again). -- Neil Cerutti We will sell gasoline to anyone in a glass container. --sign at Santa Fe gas station -- http://mail.python.org/mailman/listinfo/python-list
Re: generate tuples from sequence
On 2007-01-17, Will McGugan [EMAIL PROTECTED] wrote:
Hi,
I'd like a generator that takes a sequence and yields tuples containing
n items of the sqeuence, but ignoring the 'odd' items. For example
take_group(range(9), 3) - (0,1,2) (3,4,5) (6,7,8)
This is what I came up with..
def take_group(gen, count):
i=iter(gen)
while True:
yield tuple([i.next() for _ in xrange(count)])
Is this the most efficient solution?
This is starting to seem like an FAQ. ;)
The Python library contains a recipe for this in the itertools
recipes in the documentation (5.16.3).
def grouper(n, iterable, padvalue=None):
grouper(3, 'abcdefg', 'x') -- ('a','b','c'), ('d','e','f'), ('g','x','x')
return izip(*[chain(iterable, repeat(padvalue, n-1))]*n)
It's more general and cryptic than what you asked for, though.
--
Neil Cerutti
We're not afraid of challenges. It's like we always say: If you want to go out
in the rain, be prepared to get burned. --Brazillian soccer player
--
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Re: A note on heapq module
On 2007-01-18, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Neil Cerutti: One more idea, cribbed from the linked list thread elsewhere: it might be nice if your Heap could optionally use an underlying collections.deque instead of a list. I don't know how excellent Python's deque is, but it's possible a deque would provide a faster heap than a contiguous array. C++'s std::deque is the default implementation of C++'s std::priority_queue for that reason (unless I'm confused again). If you have some minutes you can do few speed tests and show us the code and the timing results... I'll see what I can come up with. I'll have to test using the native Python implementation, which should work with deque, rather than the optimized C implementation, which doesn't. Unfortunately the inability to take advantage of the C implementation of heapq might swamp any possible advantage of using deque instead of list in a Heap class. -- Neil Cerutti -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: One more regular expressions question
On 2007-01-18, Victor Polukcht [EMAIL PROTECTED] wrote: My pattern now is: (?Pvar1[^(]+)(?Pvar2\d+)\)\s+(?Pvar3\d+) And i expect to get: var1 = Unassigned Number var2 = 1 var3 = 32 I'm sure my regexp is incorrect, but can't understand where exactly. Break it up using verbose notation to help yourself. Also, use more helpful names. With names like var1 and var2 you might as well not used named groups. r = re.compile(r(?x) (?Perror [^(]+ ) (?Perrno \d+ ) \) \s+ (?Plineno \d+ )) This way it's clearer that there's a \) with no matching \(. -- Neil Cerutti This team is one execution away from being a very good basketball team. --Doc Rivers -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: A note on heapq module
On 2007-01-18, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Neil Cerutti: One more idea, cribbed from the linked list thread elsewhere: it might be nice if your Heap could optionally use an underlying collections.deque instead of a list. I don't know how excellent Python's deque is, but it's possible a deque would provide a faster heap than a contiguous array. C++'s std::deque is the default implementation of C++'s std::priority_queue for that reason (unless I'm confused again). If you have some minutes you can do few speed tests and show us the code and the timing results... collections.deque is the loser. Here's the output of the program from my last run: list: 5.81679827554 deque: 6.40347742423 C heapq: 2.24028186815 Here's the program. You can customize it somewhat to attempt to model a real program. It builds up a heap of random integers to some size, performs random pushes and pops for a while, and then pops the heap down until it's empty. import random import timeit OPCOUNT = 5000 HEAP_SIZE = 100 # Create a random sequence of pushes and pops. pushes = 0 ops = [] for i in xrange(OPCOUNT): x = random.randint(0, 1) if x == 0 or pushes HEAP_SIZE: pushes += 1 ops.append(0) else: pushes -= 1 ops.append(1) # Pop off the rest for i in xrange(pushes): ops.append(1) def test(mod, cont): for op in ops: if op: mod.heappop(cont) else: mod.heappush(cont, random.randint(0, 150)) # heapqd is the pure Python heapq module without the C implementation. t1 = timeit.Timer(test(heapqd, list()), from __main__ import test; import heapqd) t2 = timeit.Timer(test(heapqd, deque()), from __main__ import test; \ from collections import deque; \ import heapqd) t3 = timeit.Timer(test(heapq, list()), from __main__ import test; import heapq) print list:, t1.timeit(100) print deque:, t2.timeit(100) print C heapq:, t3.timeit(100) -- Neil Cerutti The Pastor would appreciate it if the ladies of the congregation would lend him their electric girdles for the pancake breakfast next Sunday morning. --Church Bulletin Blooper -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Traversing the properties of a Class
On 2007-01-18, EdG [EMAIL PROTECTED] wrote: For debugging purposes, I would like to traverse the class listing out all the properties. This is the first thing that came to mind. def show_properties(cls): for attr in dir(cls): if isinstance(getattr(cls, attr), property): print attr -- Neil Cerutti -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: How can I create a linked list in Python?
On 2007-01-18, sturlamolden [EMAIL PROTECTED] wrote: Paul Rubin wrote: But that's what Lisp does too. Ok, I may have to reread Paul Graham's book on ANSI Common Lisp then. Here's something silly I whipped up to play with. r Lisp style singly-linked lists called llist. def consp(o): return isinstance(o, Cons) def car(c): Return the car of a lisp-list. Undefined for nil. if null(c): raise AttributeError(nil has no cdr) return c.car def cdr(c): Return the cdr of a lisp=list. if null(c): return nil return c.cdr def cons(o, c): Build a new cons cell from an object and a Cons. return Cons(o, c) def null(c): return c is nil def rplaca(c, o): c.car = o return c def rplacd(c, o): c.cdr = o return c def llist(li): Build a llist from a list. c = nil for a in reversed(li): if isinstance(a, list): c = cons(llist(a), c) else: c = cons(a, c) return c class Cons(object): def __init__(self, car, cdr): self.car = car self.cdr = cdr def __repr__(self): def helper(li, s): if null(li): return s + ) else: return helper(cdr(li), s + %s % repr(car(li))) return helper(self.cdr, ( + repr(self.car)) class Nil(Cons): def __init__(self): Cons.__init__(self, None, None) def __repr__(self): return '()' nil = Nil() print cons(5, nil) print cons(5, cons(3, nil)) print cons(cons(5, (cons(7, nil))), cons(cons(5, cons(3, nil)), nil)) print nil print llist([1, ['a', 'b', 'c'], 2, 3]) There's lots more more stuff to add, but the fun wore out. I'd like if it the cdr of nil could actually be nil, instead of None with a special case in cdr, but I couldn't figure out a neat way to do it. -- Neil Cerutti I've had a wonderful evening, but this wasn't it. --Groucho Marx -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: OT Annoying Habits (Was: when format strings attack)
On 2007-01-20, Nick Maclaren [EMAIL PROTECTED] wrote: In article [EMAIL PROTECTED], Carroll, Barry [EMAIL PROTECTED] writes: | | My thanks to Aahz and the others who responded. I also did some | Googling on my own. I found out that top-posting is the norm in the | e-mail world. Bottom- and inline-posting are the norm in the newsgroup | world. =20 Sorry, even that is not so. I have been using Email since the 1960s, and top-posting has been used only by the inconsiderate. ...or the beleaguered. Since my school's IT switched to Exchange, correct email composition is really annoying. The only way to do it is to manually cut into a real editor, and then past back in the entire message. This is not worth the hassle for interoffice communication, since everyone else is stuck with stupid top-posting, too. It's been an interesting journey, from some unix-based terminal email, to Lotus Notes (ARRGH!), then a happy time using IMAP, and now back to (ARRGH!). -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Are there sprintf in Python???
On 2007-01-22, questions? [EMAIL PROTECTED] wrote: Are there any sprintf in Python? I know you can print to files(or redefine sys.stout) and later open the file content. Are there similar function to sprintf in C? No, but you can compose a similar function very easily. def sprintf(format, *objects): return format % tuple(objects) Since strings are immutable it's not convenient to provide a pass-out parameter as in C. If you want to check for errors you'll have to catch the exceptions, rather than inspect the return value as you can in C. -- Neil Cerutti Symphonies of the Romantic era were a lot longer in length. --Music Lit Essay -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Best way to document Python code...
On 2007-01-22, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Boris Ozegovic: Does Python has API just like in Java, for example http://java.sun.com/j2se/1.5.0/docs/api/allclasses-noframe.html ctrl-f and than click on class you are searching for, and finally you get clean list of all fields and methods. Where can I find similar in Python, for example, if I would like to see which methods list/dictionary has. You can do that from the shell, with help(name) or dir(name), where name can be a class, object, most things. It is OK for a lark, but sadly dir is not suitable enough. You do need to refer to the documentation off-line or you'll miss vital entries. It won't hurt to read effbot.org, either, as I keep finding out. Also check out the interactive help system. If you've got the html versions of the docs installed, it functions somewhat like perldoc. Type help() at the interactive prompt to get started. -- Neil Cerutti Will the last person to leave please see that the perpetual light is extinguished --sign at New England church -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: match nested parenthesis
On 2007-01-23, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: hi i wish to find an reg exp for matching nested parenthesis of varying level like string = It is not possible, because the set of strings containing balanced parenthesis is not regular. Python re's aren't *really* regular expressions, so you might be able to hack something up using extensions (I'm not sure if it's been proven that you can'). I believe regexes are the wrong tool for the job. somewords1(words(somewords2)-(some(some)words3)somestuff)somestuff and be able to evaluate the pair starting from the inner most(the deepest level) , ie (some) up till the outer most. What is a good reg exp to do this? or is simple string manipulations enough? Write a context free grammar and a recognizer for that grammar, instead. Python developers haven't been able to agree on any such module to include in the standard distribution yet, unfortunately. But fortunately (consequently), there are tons of nice parser and scanner generators available on the net. Try pyparsing for a start, as it's a recent, maintained package with excellent support on this group at the moment. Or just compose your own little function by hand. A stack-based solution (implemented using a list as a stack) should be easy enough. -- Neil Cerutti And now the sequence of events in no particular order. --Dan Rather -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Thoughts on using isinstance
On 2007-01-24, abcd [EMAIL PROTECTED] wrote: In my code I am debating whether or not to validate the types of data being passed to my functions. For example def sayHello(self, name): if not name: rasie name can't be null if not isinstance(name, str): raise name must be a string print Hello + name Is the use of isinstance a bad way of doing things? is it a heavy operation? for example, if I use this in each function validate input will it slow things down a lot? just curious how you might handle this type of situation (other than not validating at all). Validation of parameters is an excellent idea, but *not* validation of datatypes. The problem is that sayHello can function properly with many more objects than just strings, if you write it differently. The following version accepts any iterable over strings. def sayHello(self, name): it = iter(name) print Hello, ''.join(it) It still lacks validation. But to validate a name you will need to conceive a set of regular strings that contains every name you'd like to accept. Names probably aren't worth validating, although you might reasonably reject a few things, like the empty string. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-thinking my if-thens - a software engineering question
On 2007-01-24, metaperl [EMAIL PROTECTED] wrote:
if dict_key == 'PCN':
fields = dict_val.split(/)
mo = re.match( '(\w{2})(\d{2})(\d{2})' , fields[1] )
if mo:
dict_val = %s/%s%s/%s % (fields[0], mo.group(1),
mo.group(3),
fields[2][1:])
else:
dict_val = dict_val
Ok, so now here is what has happened. This code was based on
the assumption that dict_val would have 2 forward slashes in
it. It turns out that I need to follow a different process of
massaging when no slashes are present. A naive solution would
be something like:
if dict_key == 'PCN':
fields = dict_val.split(/)
if fields == 3:
dict_val = pcn_three(fields) # where pcn_three
is the code above
else:
# new logic
But I am wondering if I should abstract the flow of control
into a class or something.
This is what I do in Python when a new requirement pops up:
1. Write the simplest/first thing that comes to mind to fix it.
1. a) Am I done? Probably. But maybe not.
2. Now I examine what I've written to see the lay of the code.
Only after writing something new once do I usually have
enough information to write it better. In other words,
writing the code organizes my thoughts. I usually have to
fully understand something, even to get a kludgey solution to
work. The Kludgey solution informs the design of something
better.
2. a) Got to 1. a)
In the case above, I've tried to figure out what you're
specifically doing, and failed. So I don't have more specific
advice.
--
Neil Cerutti
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Re: Static variables
On 2007-01-24, Florian Lindner [EMAIL PROTECTED] wrote: does python have static variables? I mean function-local variables that keep their state between invocations of the function. Yup. Here's a nice way. I don't how recent your Python must be to support this, though. def foo(x): ... print foo.static_n, x ... foo.static_n += 1 ... foo.static_n = 0 for i in range(5): ... foo(?) ... 0 ? 1 ? 2 ? 3 ? 4 ? If you need to use an earlier version, then a boxed value stored as a keyword parameter will also work. def foo(x, s=[0]): ... print s[0], x ... s[0] += 1 ... for i in range(5): ... foo(!) ... 0 ! 1 ! 2 ! 3 ! 4 ! The latter is not as nice, since your static variable is easy to clobber by passing something into the function. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Please have a look at this class
On 2007-01-25, antred [EMAIL PROTECTED] wrote: While working on a program I encountered a situation where I'd construct a largish data structure (a tree) from parsing a host of files and would end up having to throw away parts of my newly built tree if a file turned out to contain invalid data. The first idea that occurs to me is to provide a merge function for your data structure, which you use to merge in another tree object when that data is known to be valid. So the process would work like this: temp_tree = process(the_file) if temp_tree.is_valid(): real_tree.merge(temp_tree) CODE SNIPPET u = Unrollable() u.someValue = 3.14 u.aString = 'Hi there' # If we decide we want to keep those changes ... u.commit() # Or we could have reverted to the original. This would have restored the state prior to the last call to commit() (or simply the state at the beginning, if there hasn't been a call to commit yet). #u.rollback() /CODE SNIPPET The basic idea behind this is that each instance of the Unrollable class keeps an internal dictionary (which, in lieu of a better name I'm currently calling 'sand box') to which all changed attribute values are saved (attribute changes are intercepted via __setattr__). Then, with a call to commit(), all attributes are transferred to the instance's __dict__ dictionary and hence become actual attributes per se. A nice use for this class might be to pass large mutable objects to a functions as if it were immutable without needing to copy them. Unfortunately it only works for one level of call. I think. -- Neil Cerutti -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: python+ncurses: I can't display accents
On 2007-01-26, Fabrice DELENTE [EMAIL PROTECTED] wrote: I'm trying to display french characters (è -- that's e grave -- or à -- agrave) in python 2.5, with the ncurses wrapper that comes it, and I can't. My locale is set correctly (fr_FR.iso885915), and my terminal (rxvt-unicode) is able to display those chars. What have you tried? -- Neil Cerutti -- Posted via a free Usenet account from http://www.teranews.com -- http://mail.python.org/mailman/listinfo/python-list
Re: python+ncurses: I can't display accents
On 2007-01-26, Fabrice DELENTE [EMAIL PROTECTED] wrote:
What have you tried?
I've tried
stdscr.addstr(0,0,aéïoù)
or
stdscr.addstr(0,0,leçon)
The ASCII chars show correctly, but the accented characters
don't, so I see 'ao' or 'leon' on the screen.
The term in which I display is 8-bit-able, so the problem is
either on ncurses side, or on python side.
What happens when you try this?
stdscr.addstr(0,0, uleçon.encode('iso8859-15'))
I don't really expect it to work, but if anything will, that is
it. Curses supports only ASCII and a some special symbol codes
defined by curses.
I have
#!/usr/local/bin/python
#coding: iso8859-15
Be sure to write your non-ASCII strings as unicode literals, and
then encode them just before displaying or storing them
somewhere.
--
Neil Cerutti
--
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Re: Convert String to list of chars
On 2007-01-27, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: How can I convert a string to a char list? for example hello -- ['h','e','l','l','o'] I have been searching but I can't find my answers list(hello) -- http://mail.python.org/mailman/listinfo/python-list
Re: python+ncurses: I can't display accents
On 2007-01-27, Thomas Dickey [EMAIL PROTECTED] wrote: Neil Cerutti [EMAIL PROTECTED] wrote: I don't really expect it to work, but if anything will, that is it. Curses supports only ASCII and a some special symbol codes defined by curses. un - no. Curses supports whatever the flavor of curses you have does. Often that's the 8-bit flavor of ncurses, but the limitation is definitely in the python configuration. Thanks for the clarification. I was going by the some Python documentation, but I did notice contradictory information in other discussion. The 8-bit ncurses is supposed to support iso-8859-1 through iso-8859-15, i.e., all the byle encodings. I don't know why Python's bindings don't work. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Help me understand this
On 2007-01-30, Gabriel Genellina [EMAIL PROTECTED] wrote: En Tue, 30 Jan 2007 06:34:01 -0300, Beej [EMAIL PROTECTED] escribió: But here's one I still don't get: type(2) type 'int' type((2)) type 'int' (2).__add__(1) 3 2.__add__(1) File stdin, line 1 2.__add__(1) ^ SyntaxError: invalid syntax It appears to be a bug, either in the grammar implementation, or in the grammar documentation. These are the relevant rules: attributeref ::= primary . identifier primary ::= atom | attributeref | subscription | slicing | call atom ::= identifier | literal | enclosure literal ::= stringliteral | integer | longinteger | floatnumber | imagnumber An integer is a primary so 2.__add(1) should be valid. Not if the tokenizer passes the parser a float. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: division by 7 efficiently ???
On 2007-02-01, Michael Yanowitz [EMAIL PROTECTED] wrote: I think it is off by 1 in small numbers, off by a little more with large numbers: def div7 (N): ...return (N3) + ((N-7*(N3))3) ... div7 (70) 9 div7 (77) 10 div7 (700) 98 div7 (7) 0 div7 (10) 1 div7 (14) 1 div7 (21) 2 div7 (700) 98 div7 (7000) 984 Heh, heh. That's reminding of the fabulous O(n) Dropsort algorithm I saw linked from Effbot's blog. -- Neil Cerutti I'm tired of hearing about money, money, money, money, money. I just want to play the game, drink Pepsi, wear Reebok. --Shaquille O'Neal -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I print out in the standard output coloured lines
On 2007-02-02, rzed [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote in news:[EMAIL PROTECTED]: On Feb 2, 1:16 pm, rzed [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote innews:[EMAIL PROTECTED]: Hi, I'm interested in printing out coloured lines of my application and I don't know what to use. Can anybody give me an idea?? You could speed up the process if you explain what your application is and what you mean by colored lines. Does your application emit output to a plotter, an ink-jet printer, or a color laser printer? Is it a drawing program? An editor in which you want lines colored to highlight context? It might be useful to know what system you are running as well. Just a little detail here. -- rzed Well, yes, it's a program that prints out lines to the standard output with a print command, and I want to print them coloured. For example: print Hello World!! I want it in red colour. That's all. If you're on Linux, you could use the curses module. There may be a precompiled Windows version compatible with your Python version, or maybe not, but the Windows source is available, and you may be able to get it to work with your Python with some effort. Linux distros include curses, I think. For Windows curses, take a look at http://adamv.com/dev/python/curses/. You will understand why the phrase Windows curses is used, I expect. On Windows, there's pdcurses for DOS or ncurses for the Cygwin platform, but I don't know how to get either to work with Python. Far simpler to get working in Windows is Fredrik Lundh's Console. http://www.effbot.org/downloads/#console If you're using Windowd 98 or earlier there are versions of a Python readline library that provide cursor addressing and color using the ANSI excape sequences. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: need help on a data structure problem
On 2007-02-02, Ben Finney [EMAIL PROTECTED] wrote: Dongsheng Ruan [EMAIL PROTECTED] writes: Not quite related with Python. But my Data Structure course is experiemented on python and there is no data structure group, So I have to post here: Better, you should discuss it in your class, with your teacher. Also: comp.algorithms is the usual Usenet place for discussion of algorithms and data structures. However most of the talk there is pretty high-falutin'. -- Neil Cerutti It isn't pollution that is hurting the environment; it's the impurities in our air and water that are doing it. --Dan Quayle -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
On 2007-02-02, Ben Finney [EMAIL PROTECTED] wrote: James Stroud [EMAIL PROTECTED] writes: Ben Finney wrote: The Python runtime parser is designed to parse Python, not some arbitrary language that someone chooses to implement in Python. You haven't addressed why the limitation isn't arbitrary. Good thing I wasn't trying to do that, then. I was pointing out the source of the limitation. The Python syntax parser must follow the rules of the Python language. If you accept that premise, it follows that the '~' operator is unary only. If you *don't* accept that premise, I have no help to offer. There's been only one (or two?) languages in history that attempted to provide programmers with the ability to implement new infix operators, including defining precedence level and associativity (I can't think of the name right now). C++, for example, works the same way as Python here. You can override most of the operators, but you cannot change their arity, associativity, or precedence level. -- Neil Cerutti Let us join David and Lisa in the celebration of their wedding and bring their happiness to a conclusion. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: newbie/ merging lists of lists with items in common
On 2007-02-02, ardief [EMAIL PROTECTED] wrote: Hi everyone Here is my problem: I have a list that looks like this - [['a', '13'], ['a', '3'], ['b', '6'], ['c', '12'], ['c', '15'], ['c', '4'], ['d', '2'], ['e', '11'], ['e', '5'], ['e', '16'], ['e', '7']] and I would like to end up with something like this, i.e. with the only one list per letter: [['a', ['13' '3']], ['b', '6'], ['c', ['12', '15', '4']], ['d', '2'], ['e', ['11', '5', '16', '7']]] I have the feeling it's trivial, and I've scoured the group archives - sets might be a possibility, but I'm not sure how to operate on a list of lists with sets. This is a job for... duhn-duhn-DH! Captain CHAOS! Er... I mean itertools.groupby. I took the liberty of not assuming the alist was sorted already. This could be a one-liner if you wanted to be evil. def bundle_alist(seq): Bundle together some alist tails. seq = [['a', '13'], ['a', '3'], ['b', '6'], ['c', '12'], ['c', '15'], ['c', '4'], ['d', '2'], ['e', '11'], ['e', '5'], ['e', '16'], ['e', '7']] bundle_alist(seq) [['a', ['13', '3']], ['b', ['6']], ['c', ['12', '15', '4']], ['d', ['2']], ['e', ['11', '5', '16', '7']]] from itertools import groupby def key_func(t): return t[0] groups = groupby(sorted(seq, key=key_func), key_func) seq = [] for item in groups: seq.append([item[0], [a[1] for a in item[1]]]) return seq -- Neil Cerutti Music gets more chromatic and heavy towards the end of the century. One of the popular questions of the day was, Why? --Music Lit Essay -- http://mail.python.org/mailman/listinfo/python-list
Re: newbie/ merging lists of lists with items in common
On 2007-02-02, Laurent Pointal [EMAIL PROTECTED] wrote: Neil Cerutti a écrit : On 2007-02-02, ardief [EMAIL PROTECTED] wrote: zip This is a job for... duhn-duhn-DH! Captain CHAOS! Er... I mean itertools.groupby. zip def key_func(t): return t[0] Not needed: -- from operator import itemgetter I agree. But I used it anyway, to make it easier to see that the sort and the groupby must be and are using the same key function. In this case I admit it's a not a huge readability win, but I was also following the Do Not Repeat Yourself Rule, which makes the key function easier to refactor. See in the example: http://docs.python.org/lib/itertools-example.html So much stuff in libraries, so few we know. Thanks to doc writers, Usenet contributors Google search engines. Yup. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pythonish code
On 2007-02-02, Toby A Inkster [EMAIL PROTECTED] wrote: Mizipzor wrote: One thing is that in c++ im used to have private members in classes and no member is altered except through the public functions of the class. By convention, class members starting with a single underscore are considered private. An important consideration is that this convention is simply a lower level of enforcement than C++ provides. Private members in C++ are accessible if you use pointers. Class members starting with a double underscore are mangled which makes it more difficult for other code (even subclasses!) to access the member. Difficult though -- not impossible. I think it's best to never use such names in new code. Python's mangling is troubled, since it uses unqualified names in the mangle, resulting in ambiguity. -- Neil Cerutti Ushers will eat latecomers. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: Checking default arguments
On 2007-02-02, Igor V. Rafienko [EMAIL PROTECTED] wrote:
Hi,
I was wondering whether it was possible to find out which
parameter value is being used: the default argument or the
user-supplied one. That is:
def foo(x, y=bar):
# how to figure out whether the value of y is
# the default argument, or user-supplied?
foo(1, bar) = user-supplied
foo(1)= default
{}.pop seems to be able to make this dictinction.
You can fake it (this may be how dict.pop work) by not providing
defaults, but using positional arguments.
Here's a silly example, which returns a tuple if the user
supplies the second argument, and a list otherwise.
def foo(x, *args):
if len(args) == 0:
y_provided = True
y = bar
else:
y_provided = False
y = args[0]
if y_provided:
return (x, y)
else:
return [x, y]
--
Neil Cerutti
Wonderful bargains for men with 16 and 17 necks --sign at clothing store
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Re: How to suppress DeprecationWarning: Old style callback, use cb_func(ok, store) instead
On 2007-02-03, Gabriel Genellina [EMAIL PROTECTED] wrote: En Sat, 03 Feb 2007 06:12:33 -0300, Peter Otten [EMAIL PROTECTED] escribió: John Nagle wrote: How do I suppress DeprecationWarning: Old style callback, use cb_func(ok, store) instead. A library is triggering this message, the library is being fixed, but I need to make the message disappear from the output of a CGI program. import warnings warnings.filterwarnings(ignore, message=Old style callback, use cb_func(ok, store) instead) Or you can be more aggressive and filter out all DeprecationWarnings: warnings.simplefilter(ignore,DeprecationWarning) (same as using option -Wignore::DeprecationWarning on the python command line) Ah, yes! The null module. Python should have more of these. I mean shouldn't. ;) -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: confused about resizing array in Python
On 2007-02-04, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: How about the traditional programming languages like C, Pascal or C++? For a start they don't have a built in list type. C and Pascal don't even have one in the standard library. C++ has STL vectors and if you, the programmer, decide to store pointers in it instead of structures or objects then you have something like Python's list type. You need to store some form of smart pointer (rather than a bare pointer) in C++ standard containers in order to avoid heart, head and stomach aches. A reference counted pointer type will come fairly close to Python semantics. -- Neil Cerutti Eddie Robinson is about one word: winning and losing. --Eddie Robinson's agent Paul Collier -- http://mail.python.org/mailman/listinfo/python-list
Re: HELP NEEDED ... Regd. Regular expressions PyQt
On 2007-02-03, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I am trying to work out a regular expression in a PyQt environment for time in hh:mm:ss format. Any suggestions? After you find your time in hh:mm:ss format, be sure to check out time.strptime for a quick conversion. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Trouble fixing a broken ASCII string - replace mode in codec not working.
On 2007-02-06, Robert Kern [EMAIL PROTECTED] wrote:
John Nagle wrote:
File D:\projects\sitetruth\InfoSitePage.py, line 285, in httpfetch
sitetext = sitetext.encode('ascii','replace') # force to clean ASCII
UnicodeDecodeError: 'ascii' codec can't decode byte 0x92 in
position 29151: ordinal not in range(128)
Why is that exception being raised when the codec was told 'replace'?
The .encode('ascii') takes unicode strings to str strings.
Since you gave it a str string, it first tried to convert it to
a unicode string using the default codec ('ascii'), just as if
you were to have done unicode(sitetext).encode('ascii',
'replace').
I think you want something like this:
sitetext = sitetext.decode('ascii', 'replace').encode('ascii', 'replace')
This is the cue for the translate method, which will be much
faster and simpler for cases like this. You can build the
translation table yourself, or use maketrans.
asciitable = string.maketrans(''.join(chr(a) for a in xrange(127, 256)),
...'?'*127)
You'd only want to do that once. Then to strip off the non-ascii:
sitetext.translate(asciitable)
I used a similar solution in an application I'm working on that
must uses a Latin-1 byte-encoding internally, but displays on
stdout in ascii.
--
Neil Cerutti
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Re: Vim search under cursor
On 2007-02-07, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Hi, I am using gvim to edit python source files. When I press * or #, I would want to search for the attribute name under the cursor and not the entire string. For example, If I have os.error and pressing * on top of error searches for os.error rather than error. How to set this, any Idea? It's will to break things, but you can do this by editing the iskeyword string and adding in the '.'. :h 'iskeyword'. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: doctests for interactive functions
On 2007-02-08, Brian van den Broek [EMAIL PROTECTED] wrote: All classes take an optional argument input_function that determines how the class instance gets its input. If this is not provided, it defaults to raw_input. doctest tests reassign it so that they can be run automatically. What I've done in these cases is create a file containing my test input, and before running the doctests I remap sys.stdin to my file of test data. Then you don't need test code cluttering up your functions. -- Neil Cerutti We don't necessarily discriminate. We simply exclude certain types of people. --Colonel Gerald Wellman -- http://mail.python.org/mailman/listinfo/python-list
Re: doctests for interactive functions
On 2007-02-08, Brian van den Broek [EMAIL PROTECTED] wrote: Can I run the rough structure of my code past you to see if it is in the vicinity of what you mean? (I have removed some details for sake of a short(er :-)) post.) Yes, this is a good way to think about it. Separate input from validation. The downside is that control flow grows warts. My .get method looks like: def get(self, input_function=raw_input): while True: self._prompt_user() self._input = input_function() if self._is_valid_input(): break else: self._process_invalid_input() self._set_data() The base class ._prompt_user just displays a prompt. Individual subclasses might implement ._prompt_user to both display a prompt, and further information about constraints on valid inputs, or generate a menu of options on the fly, etc. Subclasses implement ._is_valid_input to return True if the input meets the desired constraints, False otherwise. So, YesNo._is_valid_input ensures that ._input.lower() is in ['y', 'n', 'yes', 'no'], for instance. Your scheme may run into trouble with unexpected end of file when input_function is not raw_input. File methods don't raise an exception for EOF, they just return , the empty string. So you may need to check of that return value, and raise IOError for that case. ._process_invalid_input is implemented to provide useful feedback about invalid input. So, YesNo._process_invalid_input() emits a reminder that a value in ['y', 'n', 'yes', 'no'] is needed, for instance. ._set_data is usually implemented to just store the user's input as .data, but in some cases, it first subjects it to further processing. For instance YesNo._set_data sets .data to True if the user entered a yes value, False if they entered a no value. Is this the sort of thing you mean, or is this the sort of coupling you suggest I avoid? It has to be coupled somewhere. This seems like a good place to do it. The private methods can all be tested individually, so the doctests for get can be quite simple, or even absent. Note that sequestering the test input in a file doesn't allow for good examples, unfortunately. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Is Python for me?
On 2007-02-09, jiddu [EMAIL PROTECTED] wrote: Hi, I'm planning to create a poker calculator, I learned some basic in highschool years ago and I was told for beginners Python is a good language to start. Python *is* a good language to start. What I wanted to do is to first write a program which will be able to run through all the possible combinations of cards dealt out and use some counters to calculate different probabilities at different stages. Since that is a lot of data I think I have to store it in some kind of database or spreadsheet type thing? Unfortunately, that is a very *difficult* problem; no programming library (save a hypothetical poker probability library) can make it easy. Then I wanted to write a simple user interface so I could use my mouse to make selections of cards that I am dealt and that come on the flop and how many opponents and have the program find the calculated information and display it on the screen. I am wondering if I learn to use Python will I be able to write something like this? My friend studied some C in college so I thought I'd learn C++, turns out it is a very complicated language so I thought maybe I should try something else before I commit more time to the language. Python can help you with creating an user interface, and with several simple, powerful data structures. I think you ought to lower your ambition a bit, at first. Firts write a program to rank complete sets of poker hands. That should hold you for a while. -- Neil Cerutti The recording I listened to had Alfred Brendel doing the dirty work of performing this sonata (Liszt B minor) --Music Lit Essay -- http://mail.python.org/mailman/listinfo/python-list
Re: How to find all the same words in a text?
On 2007-02-10, Johny [EMAIL PROTECTED] wrote: I need to find all the same words in a text . What would be the best idea to do that? I used string.find but it does not work properly for the words. Let suppose I want to find a number 324 in the text '45 324 45324' there is only one occurrence of 324 word but string.find() finds 2 occurrences ( in 45324 too) Must I use regex? Thanks for help The first thing to do is to answer the question: What is a word? The second thing to do is to design some code that can find words in strings. The last thing to do is to search those actual words for the word you're looking for. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: gvim: doc string editing
On 2007-02-11, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Hi, I am using gvim, and am looking for a way to tell gvim to automatically wrap long lines into multiple lines ( by automatically inserting the newline character) when I edit doc strings. I am sure somebody must have done this. If tw (textwidth) is set to some apposite number, then it should just work (unfortunately, this will also cause your code to wrap unless you set up the comment strings properly for Python). Alternatively, you can use the gq formatting command to wrap the comment after it is composed. Do :h format_comments for the full dope. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On 2007-02-10, Geoff Hill [EMAIL PROTECTED] wrote: What's the way to go about learning Python's regular expressions? I feel like such an idiot - being so strong in a programming language but knowing nothing about RE. A great way to learn regular expressions is to implement them. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
