Sort list as if it were numbers



Published: 2018-04-14 10:27:34 +0000
Categories: Python,

Language

Python

Description

In BASH you might quite often use sort -n to ensure that strings are sorted as if they were numeric (i.e. so 12a,2a,4a is sorted into the order you'd expect based on the integers at the front).

There isn't a direct way to do this to a list in Python, so you need a wrapper to help implement the functionality

Similar to

  • BASH - sort -n

Based On

Snippet

import re
def sorted_nicely( l ):
    """ Sorts the given iterable in the way that is expected.

    Required arguments:
    l -- The iterable to be sorted.

    From https://arcpy.wordpress.com/2012/05/11/sorting-alphanumeric-strings-in-python/
    and http://stackoverflow.com/questions/2669059/how-to-sort-alpha-numeric-set-in-python    

    """
    convert = lambda text: int(text) if text.isdigit() else text
    alphanum_key = lambda key: [convert(c) for c in re.split('([0-9]+)', key)]
    return sorted(l, key = alphanum_key)

Usage Example

a = ['1a','12a','21c','3b','4a','5a']

print sorted(a)
# ['12a', '1a', '21c', '3b', '4a', '5a']

print sorted_nicely(a)
# ['1a', '3b', '4a', '5a', '12a', '21c']

Keywords

alphanumeric, sorting, strings, sort, number, integer, numeric sort,

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