Sorting Non-Alphanumeric Lists with os.listdir() in Python

  1. Introduction
  2. Sorting Non-Alphanumeric Lists
  3. Conclusion


When working with files and directories in Python, the os module provides a convenient way to access and manipulate them. One of the most commonly used functions in os is os.listdir(), which returns a list of all the files and directories in a given path. However, by default, the returned list is sorted in lexicographic order, which can be problematic when dealing with non-alphanumeric filenames or directory names.

In this article, we will explore how to sort non-alphanumeric lists with os.listdir() in Python.

Sorting Non-Alphanumeric Lists

To sort non-alphanumeric lists with os.listdir(), we can use the sorted() function along with a custom key function. The key function takes a string as input and returns a tuple that will be used for sorting.

For example, let's say we have a directory containing the following files:

  • file1.txt
  • file10.txt
  • file11.txt
  • file2.txt
  • file3.txt

If we use os.listdir(), the returned list will be sorted as follows:

['file1.txt', 'file10.txt', 'file11.txt', 'file2.txt', 'file3.txt']

To sort this list in a natural order, we can define a custom key function that splits each filename into a tuple consisting of integers and strings. The integers are converted to integers, and the strings are left as strings.

Here's an example implementation:

import re

def natural_sort_key(s):
    return [int(s) if s.isdigit() else s.lower() for s in re.split(r'(d+)', s)]

files = os.listdir('.')
sorted_files = sorted(files, key=natural_sort_key)

This will output the following sorted list:

['file1.txt', 'file2.txt', 'file3.txt', 'file10.txt', 'file11.txt']

As you can see, the list is now sorted in a natural order, where numbers are sorted numerically and strings are sorted alphabetically.


In conclusion, sorting non-alphanumeric lists with os.listdir() in Python can be achieved by using the sorted() function with a custom key function. By defining a key function that splits each filename into a tuple of integers and strings, we can sort the list in a natural order that makes sense for file and directory names.

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