How Can I Implement Natural Sorting for Strings Containing Numbers and Floats in Python?

Natural Sorting for Strings with Numbers

When sorting strings that contain numbers, the default sorting methods may not yield the desired result. For example, the string "something12" may be placed after "something2" instead of before it.

To rectify this, we can employ natural sorting, which takes into account the numbers within the strings. Here's how:

Importing Necessary Modules:

First, we import the re module for regular expression handling.

import re

Defining Helper Functions:

We define helper functions for converting strings to integers and floats:

def atoi(text):
    return int(text) if text.isdigit() else text

def atof(text):
    try:
        retval = float(text)
    except ValueError:
        retval = text
    return retval

Defining Natural Sort Function:

The natural_keys function splits the string into its constituent parts using regular expressions:

def natural_keys(text):
    return [atoi(c) for c in re.split(r'(\d+)', text)]

Sorting with Natural Keys:

Utilizing the natural_keys function as a key for sorting places the strings in natural order:

alist = ["something1", "something12", "something17", "something2", "something25", "something29"]
alist.sort(key=natural_keys)
print(alist)

Output:

['something1', 'something2', 'something12', 'something17', 'something25', 'something29']

Handling Floats:

To sort strings containing floats, modify the regular expression in natural_keys to match floats:

def natural_keys(text):
    return [atof(c) for c in re.split(r'[+-]?([0-9]+(?:[.][0-9]*)?|[.][0-9]+)', text)]

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