gmane.comp.python.tutor

Re: Best way to define comparison

Tiago Katcipis — 2008-05-18T02:29:58

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Re: Best way to define comparison

Kent Johnson — 2008-05-17T23:36:47

It uses __eq__() if it is defined, otherwise __cmp__() http://docs.python.org/ref/customization.html Kent PS Please use Reply All to reply to the list _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

Re: Best way to define comparison

Kent Johnson — 2008-05-17T22:40:22

Use __cmp__() if it meets your needs - you just have to define one method and you get all comparisons. The other special methods - "rich comparisons" - were introduced in Python 2.1 to allow additional flexibility when __cmp__() is not adequate. http://www.amk.ca/python/2.1/index.html#SECTION000500000000000000000 Kent _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

Re: Best way to define comparison

bob gailer — 2008-05-17T19:30:46

AFAIK either approach is OK. No advantages. (Other than writing one method vs 2).

Best way to define comparison

Tiago Katcipis — 2008-05-17T18:18:38

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Re: Dictionaries or Numpy?

Adam Clarridge — 2008-05-17T16:12:10

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Re: Iterate through dictionary values and remove item

Ricardo Araoz — 2008-05-16T13:01:36

Lads... >>> d={ ... 1: {23A:[a,b,c,d], 24A:[b,c,d]}, ... 2: {23A:[a,b], 24A:[a,b,c,d]} ... } File "", line 2 1: {23A:[a,b,c,d], 24A:[b,c,d]}, ^ SyntaxError: invalid syntax >>> Let's get a proper syntax for our data before attempting to process it. _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

Re: datetime syntax error for May 8th and 9th 2008??

wesley chun — 2008-05-17T06:38:42

che, john is correct. any leading zero (0) of an integer number will be translated as base 8 or octal, which counts by 8's: 00, 01, 02, 03, 04, 05, 06, 07, 10 (decimal/base 10: 8*1+0=8), 11 (decimal: 8*1+1=9), 12 (decimal: 8*1+2=10), 13 (decimal 8+3=11), 14, 15, 16, 17 (decimal: 15), 20 (decimal: 8*2+0=16), 21 (decimal: 8*2+1=17), etc... the problem with "08" is that because you're counting by 8s, a value of "08" is invalid because the digits "8" and "9" are not part of the octal "alphabet" or character set. that is why "07" works but not "08". as an FYI, because of this confusion, starting with Python 3.0, octal numbers will require a lowercase "o" (in the same manner as hexadecimal/base 16 numbers require an "x") after leading 0, i.e., 0o7, 0o16, etc. (Oo8 is still an invalid octal number.) hope this helps!

Re: quickly pulling marbles out of urns

John Fouhy — 2008-05-17T04:51:14

Kent's suggest seems simplest: represent the marbles as a list of integers, where marbles[i] is the integer corresponding to marble i's colour. If that doesn't work (too many marbles?), maybe some kind of binary tree approach? e.g. a MarbleColour class which stores - the colour - the number of marbles with this colour - the number of marbles in the left subtree - the number of marbles in the right subtree where either subtree could be None (and thus have 0 marbles). Set the binary tree up initially so it's balanced by marble weight (if the marble colours are all approximately the same size at the start, you could approximate this by just filling in colours from the top in any order). Then you can randomly generate a colour by generating a random int in (0,1) and comparing with the proportions in the node. Then you just have to update the weights for the colour you choose and all nodes above it. Should be log_2(n) to pick one colour and n.log_2(n) to pick colours until you run out.

Re: datetime syntax error for May 8th and 9th 2008??

John Fouhy — 2008-05-17T04:29:50

It's simpler than that... Try this: File "", line 1 x = 08 ^ SyntaxError: invalid token 8 Basically, python interprets integer literals starting with 0 as octal numbers. It's an old convention from C (or earlier?). It doesn't affect strings, so int('010') == 10 (unless you use eval). HTH!

Re: quickly pulling marbles out of urns

Kent Johnson — 2008-05-17T04:15:23

You probably know, this is called sampling without replacement. If you can put all the 'marbles' in a list, here is a promising approach: http://groups.google.com/group/comp.lang.python/browse_thread/thread/dff9425afdb744e5/6b9a84329c0815d4?lnk=raot This is probably worth looking at too though I can't understand it at this hour: http://safari.oreilly.com/0596007973/pythoncook2-CHP-18-SECT-4 Kent _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

Re: datetime syntax error for May 8th and 9th 2008??

Che M — 2008-05-17T04:18:39

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datetime syntax error for May 8th and 9th 2008??

Che M — 2008-05-17T04:09:03

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Re: Dictionaries or Numpy?

John Fouhy — 2008-05-17T00:08:15

Hi Adam, I believe a general rule of programming is: don't optimize until you know you need to. I would advise using dictionaries for simplicity. If the program turns out slower than you would like, you can use profiling tools to figure out where in the code it is spending most of its time. If this turns out to involve dictionary lookups, you could then look at changing to Numpy (hint: you could use the timeit module to benchmark dictionary access against Numpy arrays). If your program design is good, the change should be too hard. http://en.wikipedia.org/wiki/Optimization_(computer_science)#When_to_optimize

Dictionaries or Numpy?

Adam Clarridge — 2008-05-16T22:59:50

Hi, I'm writing an AI for a board game called Blokus, and I believe that the quality of the program is going to greatly depend on the efficiency of the algorithm I use to generate legal moves and rate them. I know sort of how I'm going to do this legal move generation, and I know it is going to require lots of accesses to an array of some kind which will represent the game board. I'm fairly new to Python, and I am not sure whether it would be faster for me to use a Dictionary data type to represent the board (advantages: indices can be strings or tuples, and the dictionary can store different types of data as well, so programming would be easier) or the Numpy array type (don't know much about this, but I have heard Numpy is faster). So is Numpy faster for simple array accesses? That would be valuable and I'd deal with having an integer-indexed integer array if I had to. Code might look something like this: for playable_corner in all_playable_corners: for piece in all_available_pieces: for each_square in piece: # if square is not in a legal position, don't add to list of legal moves So that if statement would be accessing the board array many many times. I guess my question is: Is there any way to test Dictionary access time vs. Numpy array access time? Thanks, Adam _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

quickly pulling marbles out of urns

Joel Miller — 2008-05-16T21:43:19

I'm looking for a faster way to do the following problem: I have an urn with many different colors of marbles in it. I pull one out and note the color. I do not replace it. For the programming of this, I actually know how many are yellow, green, etc. So the way the code works right now is: import math ... randindex = math.randint(1,number_of_marbles) for color in colors: if randindex<=marble_count[color]: #we've found what color it will be break else: #try next color randindex -= marble_count[color] marble_count[color] -= 1 number_of_marbles -= 1 return color Unfortunately, I have hundreds of thousands of colors, so it spends a while on this loop. And I have to keep choosing marbles many times at different points of the code. Is there a quicker way to do this? Thanks, Joel _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

Re: Getting started with Python

jay — 2008-05-16T16:02:44

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Re: Open a directory in the default file manager

Thomas Pani — 2008-05-16T15:55:58

> Hello, > is there any function/module that allows me to open a directory in the > default file manager of a operating system? On Windows you can use os.startfile(). On "pure" Unices there's no such thing as filetype associations However, if you use a desktop environment, you can spawn xdg-open (from xdg-utils) from Python. This will autodetect gnome, kde and xfce and use their tools (gnome-open, kfmclient, exo-open). I think on OS X/Darwin there's a similar utility called `open'. You can use sys.platform to determine which system you're running on. thomas _______________________________________________ Tutor maillist - Tutor< at >python.org http://mail.python.org/mailman/listinfo/tutor

Re: Getting started with Python

Hansen, Mike — 2008-05-16T15:57:45

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Re: Getting started with Python

jay — 2008-05-16T15:44:04

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Re: Getting started with Python

Moishy Gluck — 2008-05-16T15:20:47

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