sort string by number inside

Question

I would like to know how can I sort a string by the number inside.

As example I have:

hello = " hola %d" % (number_from_database)
bye = "adios %d" % (number_from_database_again)

I want to sort them by the number even if it changes.

Asked By: Victor Castillo Torres

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Source

Answer 1

You can pass a key to sort:

sorted(l, key=lambda x: int(re.sub('D', '', x)))

For example:

In [1]: import re

In [2]: l = ['asdas2', 'asdas1', 'asds3ssd']

In [3]: sorted(l, key=lambda x: int(re.sub('D', '', x)))
Out[3]: ['asdas1', 'asdas2', 'asds3ssd']

Where re.sub('D', '', x) replaces everything but the digits.

Answered By: Andy Hayden

Answer 2

salutations = [hello, bye]
salutations.sort(key=lambda x: int(filter(lambda s: s.isdigit(), x.split())[0]))

Answered By: mVChr

Answer 3

Just a little complement to Andy’s answer.

If you want to sort set which also contain strings without any number:

sorted(l, key=lambda x: int('0'+re.sub('D', '', x)))

, which would put those strings without any number at the very beginning.

Answered By: Yuan Tao

Answer 4

The solutions above do not work for strings with the format:

test 8 - test 18

The following code will return 818 instead of 8:

x = 'test 8 - test 18'
res = int(re.sub(r'D', '', x))
print(res)

>>> 818

The solution for this is doing a search and getting the group result:

x = 'test 8 - test 18'
res = int(re.search(r'd+', x).group())
print(res)

>>> 8

So, the final solution with this correction is:

l = [
   'test 9 - test 8',
   'test 8 - test 18'
]

l2 = sorted(l, key=lambda x: int(re.search(r'd+', x).group()))

print(l)
print(l2)

>>> ['test 9 - test 8', 'test 8 - test 18']
['test 8 - test 18', 'test 9 - test 8']

Answered By: Ângelo Polotto

sort string by number inside

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