Natural Sort of list containing paths in Python

Question

I have a list paths_list which contains the path of files(images) of a particular folder . Example:

['/home/username/images/s1/4.jpg', '/home/username/images/s1/7.jpg', 
'/home/username/images/s1/6.jpg', '/home/username/images/s1/3.jpg', 
'/home/username/images/s1/5.jpg', '/home/username/images/s1/10.jpg', 
'/home/username/images/s1/9.jpg', '/home/username/images/s1/1.jpg', 
'/home/username/images/s1/2.jpg', '/home/username/images/s1/12.jpg', 
'/home/username/images/s1/11.jpg', '/home/username/images/s1/8.jpg']

I want to sort then in the order: [/1.jpg ,2.jpg .....,/12.jpg] Neither sorting via length nor via alphabetical order is helping. What should be done here?

Answer 1

You can use sorted with a lambda. For the sorting criteria, you can use os to first pull just the file name (using basename), then you can split off just the filename less the extension (using splitext).

Lastly convert to int so you sort numerically instead of lexicographically.

>>> import os
>>> l = ['/home/username/images/s1/4.jpg', '/home/username/images/s1/7.jpg', '/home/username/images/s1/6.jpg', '/home/username/images/s1/3.jpg', '/home/username/images/s1/5.jpg', '/home/username/images/s1/10.jpg', '/home/username/images/s1/9.jpg', '/home/username/images/s1/1.jpg', '/home/username/images/s1/2.jpg', '/home/username/images/s1/12.jpg', '/home/username/images/s1/11.jpg', '/home/username/images/s1/8.jpg']
>>> sorted(l, key=lambda i: int(os.path.splitext(os.path.basename(i))[0]))
['/home/username/images/s1/1.jpg',
 '/home/username/images/s1/2.jpg',
 '/home/username/images/s1/3.jpg',
 '/home/username/images/s1/4.jpg',
 '/home/username/images/s1/5.jpg',
 '/home/username/images/s1/6.jpg',
 '/home/username/images/s1/7.jpg',
 '/home/username/images/s1/8.jpg',
 '/home/username/images/s1/9.jpg',
 '/home/username/images/s1/10.jpg',
 '/home/username/images/s1/11.jpg',
 '/home/username/images/s1/12.jpg']

Answer 2

Use natural sorting (see this question): clean code and good practice when sorting strings.

from natsort import natsorted
l = ['/home/username/images/s1/4.jpg', '/home/username/images/s1/7.jpg', '/home/username/images/s1/6.jpg', '/home/username/images/s1/3.jpg', '/home/username/images/s1/5.jpg', '/home/username/images/s1/10.jpg', '/home/username/images/s1/9.jpg', '/home/username/images/s1/1.jpg', '/home/username/images/s1/2.jpg', '/home/username/images/s1/12.jpg', '/home/username/images/s1/11.jpg', '/home/username/images/s1/8.jpg']
natsorted(l)

gives

['/home/username/images/s1/1.jpg',
'/home/username/images/s1/2.jpg',
'/home/username/images/s1/3.jpg',
'/home/username/images/s1/4.jpg',
'/home/username/images/s1/5.jpg',
'/home/username/images/s1/6.jpg',
'/home/username/images/s1/7.jpg',
'/home/username/images/s1/8.jpg',
'/home/username/images/s1/9.jpg',
'/home/username/images/s1/10.jpg',
'/home/username/images/s1/11.jpg',
'/home/username/images/s1/12.jpg']

Natural sorting sorts based on how you would read things on a computer screen (alphabetically and numerically), rather than how the computer reads the code.