Sort File-List in numerical order

[pit-ray]

Currently, if the following files exist, they are displayed in string order.

$ ls
image1.png image2.png image10.png image3.png image200.png

In labelme.

image1.png
image10.png
image2.png
image200.png
image3.png

However, I think it is natural to use a list of string numbers converted to numbers for sorting. I added a utility function for this to utils/_io.py because file names are i/o identifiers.

[wkentaro]

I'm not sure if this is a general solution? What happens if you have multiple digits splitted by _ or -?

1_1
1_100
1-10
1-11
1_1-1

[pit-ray]

This pull request seems to be closeing, but I show the result of the example below just in case.
The result is the same as natsorted in #990, and there is no dependency.

import re


def strnum_to_num(text):
    out = []
    for w in re.split(r"(\d+)", text):
        out.append(int(w) if w.isdigit() else w)
    return out

filenames = [
    "img_1.jpg",
    "img_100.jpg",
    "img_10.jpg",
    "img_11.jpg",
    "img_1-1.jpg",
    "img_12-1.jpg",
]

print("original:", filenames)
print(
    "numlist :",
    sorted(filenames, key=lambda x: strnum_to_num(x.lower()))
)

print()

filenames = [
    "image1.png",
    "image10.png",
    "image2.png",
    "image200.png",
    "image3.png",
]

print("original:", filenames)
print(
    "numlist :",
    sorted(filenames, key=lambda x: strnum_to_num(x.lower()))
)

original: ['img_1.jpg', 'img_100.jpg', 'img_10.jpg', 'img_11.jpg', 'img_1-1.jpg', 'img_12-1.jpg']
numlist : ['img_1-1.jpg', 'img_1.jpg', 'img_10.jpg', 'img_11.jpg', 'img_12-1.jpg', 'img_100.jpg']

original: ['image1.png', 'image10.png', 'image2.png', 'image200.png', 'image3.png']
numlist : ['image1.png', 'image2.png', 'image3.png', 'image10.png', 'image200.png']  

However, os_sorted in #990 is more natural.

Thanks!