How to Sort List in Python 3 Examples

This short tutorial will show you how to sort lists in Python.

Several different sorting techniques will be shown: including basic, natural, case insensitive, alphabetically.

Data used in this article:

import calendar
days = list(calendar.day_name)

the unsorted list is:

['Friday', 'Monday', 'Saturday', 'Sunday', 'Thursday', 'Tuesday', 'Wednesday']

1. Python sort list alphabetically with .sort()

Here's how you can sort a list alphabetically with Python. We are going to use method sort():

days.sort()
days

result:

['Friday', 'Monday', 'Saturday', 'Sunday', 'Thursday', 'Tuesday', 'Wednesday']

Note that this method works on the data structure. No need to assign a new variable . Default sorting is ascending. In order to change the order parameter reverse can be used:

days.sort(reverse=True)
days

result:

['Wednesday', 'Tuesday', 'Thursday', 'Sunday', 'Saturday', 'Monday', 'Friday']

2. Python sort list alphabetically with sorted()

To sort a list in Python without changing the list itself - use sorted().

sorted(days)

result:

['Friday', 'Monday', 'Saturday', 'Sunday', 'Thursday', 'Tuesday', 'Wednesday']

But the list itself is unchanged:

days

result:

['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

3. Python natural sort of list

Natural sort is closer to human perception for order. Let's illustrate it with a simple example of days. Let's have a list of days:

days = ['day5', 'Day1', 'day7', 'DAY9', 'day10', 'day_11']

Using the previous sorting methods will give result:

['DAY9', 'Day1', 'day10', 'day5', 'day7', 'day_11']

which is not what is the natural order of the days. As a human I would expect:

['Day1', 'day5', 'day7', 'DAY9', 'day10', 'day_11']

In order to achieve this we can use the Python package: natsort.

Method natsorted will be used in combination with parameters: key or alg:

from natsort import natsorted, ns
natsorted(days, key=lambda y: y.lower())

You can change the algorithm by parameter alg:

natsorted(days, alg=ns.IGNORECASE)

which will produce the same output.

If no parameter is used:

natsorted(days)

output:

['DAY9', 'Day1', 'day5', 'day7', 'day10', 'day_11']

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