Pythonic list reordering

[MRAB]

alex23 wrote:
> On Apr 9, 8:52 am, Ben Racine <i3enha... at gmail.com> wrote:
>> I have a list...
>> ['dir_0_error.dat', 'dir_120_error.dat', 'dir_30_error.dat', 'dir_330_error.dat']
>> I want to sort it based upon the numerical value only.
>> Does someone have an elegant solution to this?
> 
> This approach doesn't rely on knowing the format of the string:
> 
>>>> from string import maketrans, letters, punctuation
>>>> a = ['dir_0_error.dat', 'dir_120_error.dat', 'dir_30_error.dat', 'dir_330_error.dat']
>>>> def only_numbers(s):
> ...     nums = s.translate(None, letters+punctuation)
> ...     return int(nums)
> ...
>>>> a.sort(key=only_numbers)
>>>> a
> ['dir_0_error.dat', 'dir_30_error.dat', 'dir_120_error.dat',
> 'dir_330_error.dat']
> 
> If you're using Python 3.x, the string module has been removed, so you
> can find the maketrans function on str there.

The string module still exists in Python 3.x, but the string functions
which have been superseded by string methods have been removed.