Why Does os.listdir() Return Subdirectories in a Non-Alphanumeric Order?

Non-Alphanumeric List Order from os.listdir() Revisited

In Python's os.listdir() function, the default list of subdirectories is often returned in a seemingly illogical order. For instance, a directory containing subfolders named "run01" through "run20" might yield a list like this:

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

Unlike the previous alphanumeric order, this new ordering can appear nonsensical.

Understanding the Ordering

The order of the list returned by os.listdir() is determined by the underlying filesystem. Different filesystems employ various sorting algorithms that prioritize different properties, such as creation timestamp or file size. This variation in filesystem behavior can lead to inconsistent list order across different platforms or devices.

Solution

To obtain the desired alphanumeric order, you can utilize Python's built-in sorted function or the .sort method of a list:

• Using sorted(os.listdir()):

sorted_dir = sorted(os.listdir(os.getcwd()))

• Using .sort():

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

Both of these approaches will sort the list of subdirectories in alphanumeric order.

Additional Considerations

It's important to note that the original order of the os.listdir() list is determined by the filesystem. Therefore, the methods described above simply reorder the list rather than altering the underlying order managed by the filesystem.

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