I have the next list:
a = ['1th Word', 'Another Word', '10th Word']
print a.sort()
>>> ['10th Word', '1th Word', 'Another Word']
But I need:
['1th Word', '10th Word','Another Word']
Is there an easy way to do this?
I tried:
r = re.compile(r'(\d+)')
def sort_by_number(s):
m = r.match(s)
return m.group(0)
x.sort(key=sort_by_number)
But some strings do not have numbers and this leads to an errors. Thanks.
This is commonly called "natural sort".
See Does Python have a built in function for string natural sort? and Python analog of natsort function (sort a list using a "natural order" algorithm); also http://code.activestate.com/recipes/285264-natural-string-sorting/ and http://www.codinghorror.com/blog/2007/12/sorting-for-humans-natural-sort-order.html.
Here's a function that works for the general case
import re
def natkey(s):
return [int(p) if p else q for p, q in re.findall(r'(\d+)|(\D+)', s)]
x = ['1th Word', 'Another Word 2x', 'Another Word 20x', '10th Word 10', '2nd Word']
print sorted(x)
print sorted(x, key=natkey)
Result:
['10th Word 10', '1th Word', '2nd Word', 'Another Word 20x', 'Another Word 2x']
['1th Word', '2nd Word', '10th Word 10', 'Another Word 2x', 'Another Word 20x']
r = re.compile(r'(\d+)')
def sort_by_number(s):
m = r.match(s)
return m and m.group(0) or s
x.sort(key=sort_by_number)
Key is that if there was not match, return the string as is
