python - Non-alphanumeric list order from os.listdir()

Question

I often use python to process directories of data. Recently, I have noticed that the default order of the lists has changed to something almost nonsensical. For example, if I am in a current directory containing the following subdirectories: run01, run02, ... run19, run20, and then I generate a list from the following command:

dir = os.listdir(os.getcwd())

then I usually get a list in this order:

dir = ['run01', 'run18', 'run14', 'run13', 'run12', 'run11', 'run08', ... ]

and so on. The order used to be alphanumeric. But this new order has remained with me for a while now.

What is determining the (displayed) order of these lists?

Answer 1

You can use the builtin sorted function to sort the strings however you want. Based on what you describe,

sorted(os.listdir(whatever_directory))

Alternatively, you can use the .sort method of a list:

lst = os.listdir(whatever_directory)
lst.sort()

I think should do the trick.

Note that the order that os.listdir gets the filenames is probably completely dependent on your filesystem.