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Sorting

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The following examples were taken from http://xahlee.org/perl-python/sort_list.html .

# 1st example
li = [1,9,2,3]
li.sort()   # the list is changed IN PLACE
print li   # [1, 2, 3, 9]


# 2nd example: sort the elems by the embedded numbers
files = ['my283.jpg',
         'my23i.jpg',
         'web7-s.jpg',
         'fris88large.jpg']

def myComp(x, y):
    import re
    def getNum(str):
        return float( re.search(r'(\d+)', str).group(1) )
    return cmp(getNum(x), getNum(y))

files.sort(myComp)
print files   # ['web7-s.jpg', 'my23i.jpg', 'fris88large.jpg', 'my283.jpg']

A better way for the 2nd example:

import re

def my_func(fname):
    return int(re.search(r'\d+', fname).group())

def main():
    files = ['my283.jpg',
        'my23i.jpg',
        'web7-s.jpg',
        'fris88large.jpg']

    print sorted(files, key=my_func)

Descending order:

li = [1,9,2,3]
li.sort(reverse=True)
print li   # [9, 3, 2, 1]

This is much more efficient than sorting in ascending order first and then reversing the list.