How Can Python Efficiently Perform Natural String Sorting?

Natural Sorting in Strings

Problem Statement

Sorting strings lexicographically does not always yield the desired order. For instance, lists containing numerical values may be sorted by digit instead of the whole number. This issue stems from the default sorting mechanism, which treats each character independently.

Built-in Function

Although Python does not provide a built-in function specifically for natural string sorting, there are third-party libraries that can address this issue. One such library is natsort, which offers various methods to perform natural sorting.

natsort Library

Natsort provides two primary approaches for natural sorting: using a sorting function or a sorting key.

Sorting Function

To utilize the natsort sorting function, begin by importing it as follows:

from natsort import natsorted

You can then sort a list of strings using this function:

x = ['Elm11', 'Elm12', 'Elm2', 'elm0', 'elm1', 'elm10', 'elm13', 'elm9']
sorted_list = natsorted(x, key=lambda y: y.lower())

Alternatively, you can specify an algorithm to ignore case sensitivity:

sorted_list = natsorted(x, alg=ns.IGNORECASE)

Sorting Key

If you need to sort a list of strings using a sorting key, import the following:

from natsort import natsort_keygen

Creating a sorting key involves specifying a function to extract the key from each string, which is typically used when the strings have embedded data. For example:

keygen = natsort_keygen(key=lambda y: y.lower())
sorted_list = sorted(l1, key=keygen)

Other Options

For more complex natural sorting scenarios, the natsort library provides additional functionality and customization options. Please consult the library's documentation for further details. Additionally, as of version 7.1.0, natsort offers an os_sorted function to sort strings in the order of the local file system browser.

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