How to Achieve Natural Order Sorting in Python Like PHP's natsort Function?

Python Equivalent for PHP's natsort Function: Natural Order Sorting

The PHP natsort function is used to sort a list using a "natural order" algorithm that handles strings containing numbers in a human-readable way. Python doesn't have an exact equivalent to natsort, but there are custom solutions available.

One approach is to use a combination of Python's built-in functions:

<code class="python">import re

def try_int(s):
    "Convert to integer if possible."
    try: return int(s)
    except: return s

def natsort_key(s):
    "Used internally to get a tuple by which s is sorted."
    return map(try_int, re.findall(r'(\d+|\D+)', s))

def natcmp(a, b):
    "Natural string comparison, case sensitive."
    return cmp(natsort_key(a), natsort_key(b))

def natcasecmp(a, b):
    "Natural string comparison, ignores case."
    return natcmp(a.lower(), b.lower())</code>

To sort a list using natural order:

<code class="python">l = ['image1.jpg', 'image15.jpg', 'image12.jpg', 'image3.jpg']
l.sort(natcasecmp)</code>

Another approach that supports Unicode strings is to use a custom key function based on Python's natural_key function:

<code class="python">import re
def natural_key(string_):
    """See https://blog.codinghorror.com/sorting-for-humans-natural-sort-order/"""
    return [int(s) if s.isdigit() else s for s in re.split(r'(\d+)', string_)]</code>

Example:

<code class="python">l = ['image1.jpg', 'image15.jpg', 'image12.jpg', 'image3.jpg']
l.sort(key=natural_key)</code>

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