[Tutor] Sorting a List

[Bill Campbell]

On Wed, Jan 12, 2011, Corey Richardson wrote:
>Hello Tutors,
>
>I am generating XML definitions for animations to be used in a
>FIFE-based game. I need to sort the frames of the animations, and I am
>currently using:
>sorted([image for image in os.listdir(path) if image.endswith('.png')])
>
>The final output in the XML is:
>
>	<frame source="walk_0.png"/>
>	<frame source="walk_1.png"/>
>	<frame source="walk_10.png"/>
>	<frame source="walk_11.png"/>
>	<frame source="walk_2.png"/>
>	<frame source="walk_3.png"/>
>	<frame source="walk_4.png"/>
>	<frame source="walk_5.png"/>
>	<frame source="walk_6.png"/>
>	<frame source="walk_7.png"/>
>	<frame source="walk_8.png"/>
>	<frame source="walk_9.png"/>
>
>Having frame 10 and 11 between frame 1 and 2 is not desired behavior;
>how can I sort all of these with walk_10.png and company (this isn't the
>only animation like this) being after walk_9.png? A google search
>doesn't return anything I could use. I tried just using
>[image for image in os.listdir(path) if image.endswith('.png')],
>but that doesn't appear to have any order.

This is discussed in the Python Cookbook from O'Reilly.  If I
remember correctly, it deals exactly with the problem of sorting
file names containing numbers as you have above.

Here's a bit of code I use in a module I wrote for dealing with
RPM versions.

import re
_digits = re.compile(r'(\d+)')

def ver(s):
    r = _digits.split(s)
    r[1::2] = map(lambda x: int(x), r[1::2])
    return(tuple(r))

class FileInfo(object):
    def __init__(self, fname)
        self.fname = fname
        self.cmp = ver(fname)

    def __cmp__(self, othr):
        return cmp(self.cmp, othr.cmp)

Bill
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