os.listdir not accessing numerically labelled files in ascending order [duplicate]

Question

We want the png files to be accessed as 15.png,45.png,75.png and so on. This is the code and the output we are getting

import os
keypts_labels=[]
class_list=os.listdir('dataset')
for name in class_list:
    for image in os.listdir(f"dataset/{name}"):
        for item in os.listdir(f"dataset/{name}/{image}"):
            print(os.path.abspath(f"dataset/{name}/{image}/{item}"))

I think they want the numbers to be sorted be like 15.png 20.png 50.png . I think you can use sort on the list but I assume that didn't work. — Batselot
– Batselot, Commented Jan 6, 2022 at 11:47
There is no error, we want the files to be accessed in a sorted manner. Its accessing it randomly. @OrangoMango — Radha Mujumdar
– Radha Mujumdar, Commented Jan 6, 2022 at 11:47
They seem to be in lexicographic order, which is what I would expect. If you want them in any other order, you need to sort them using a custom key. See the dupe target. — khelwood
– khelwood, Commented Jan 6, 2022 at 12:04
The values returned from listdir() are not defined to be in any particular order. If you want them in some particular order, you will need to sort them yourself. — martineau
– martineau, Commented Jan 6, 2022 at 12:38

Kris · Accepted Answer · 2022-01-06 11:59:17Z

1

You don't need to handle all this iterating logic, when there are easy ways to do it. See the approach below

def list_files(from_folder):
    from glob import glob
    import pathlib
    # Use glob to get all files in the folder, based on the type
    png_files = glob(f"{from_folder}/**/*.png", recursive=True)
    # Use a numerical sort, using the file name prefix as the key
    png_files = sorted(png_files, key=lambda path: int(pathlib.Path(path).stem))
    
    print(png_files) #return it if you want

list_files("dataset")

This piece of function will actually list what you need. This assumes, all png files has the name a valid number, and you are searching only for png files.

I hope the logic is understood from the comments itself.

answered Jan 6, 2022 at 11:59

Kris

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