sort() in Python

The sort function can be used to sort the list in both ascending and descending order. It can be used to sort lists of integers, floating point numbers, strings, and others in Python. Its time complexity is O(NlogN).

Python sort() Syntax

The syntax of the sort() function in Python is as follows.

Syntax: list_name.sort(key=…, reverse=…)

Parameters:

By default, Python sort() doesn’t require any extra parameters and sorts the list in ascending order. However, it has two optional parameters:

• key:  function that serves as a key for the sort comparison
• reverse: If true, the list is sorted in descending order.

Return value: The sort() does not return anything but alters the original list according to the passed parameter.

What is Python sort() Function?

In Python, the sort() function is a method that belongs to the list . It is used to sort in python or the elements of a list in ascending order by default. The sort() method modifies the original list in-place, meaning it rearranges the elements directly within the existing list object, rather than creating a new sorted list.

Sort() in Python Examples

A basic example of Python sort() method.

Example : In this example the below code defines a list named unsorted_list with numeric elements. The sort() method is then applied to the list, which rearranges its elements in ascending order. The sorted list is then printed, showing the result of the sorting operation.

Output:

Now it is sorted: [2, 4, 5, 5, 6, 32, 42, 255]

Different Ways to Sort() in Python

In Python, sort() is a built-in method used to sort elements in a list in ascending order. It modifies the original list in place, meaning it reorders the elements directly within the list without creating a new list. The sort() method does not return any value; it simply sorts the list and updates it.

1. Sorting List in Ascending Order
2. Sorting List in Descending Order
3. Sort with custom function Using Key
4. Sorting List of Strings by Length
5. Sorting List of Tuples by a Specific Element
6. Sorting List of Dictionaries by a Specific Key

Sort() in Python using Sorting List in Ascending Order

The `sort()` method in Python is used to sort a list of elements in ascending order. It modifies the original list in-place, rearranging its elements to be in increasing numerical or lexicographical order. The method is applicable to lists containing numerical values, strings, or a combination of both. By default, the sort() in Python sorts a list in ascending order if we do not provide it with any parameters.

Example : In this example the below code demonstrates sorting operations on different types of lists. First, it sorts a list of integers (`numbers`) in ascending order using the `sort()` method. Next, it sorts a list of floating-point numbers (`decimalnumber`) in ascending order.

Output:

[1, 2, 3, 4]
[1.68, 2.0, 2.01, 3.28, 3.67]
['For', 'Geeks', 'Geeks']

Sort() in Python using Sorting List in Descending Order

To sort a list in descending order, set the reverse parameter to True of the sort() function in Python.

my_list.sort(reverse=True)

Example : In this example code defines three lists of different types (integers, floating-point numbers, and strings), sorts them in descending order using the `sort` method with the `reverse=True` parameter, and then prints the sorted lists.

Output:

[4, 3, 2, 1]
[3.67, 3.28, 2.01, 2.0, 1.68]
['Geeks', 'Geeks', 'For']

Sort with Custom Function Using Key

In this method describes a sorting operation with a custom function using the “key” parameter. This allows sorting based on a specific criterion defined by the custom function rather than the default ordering. The custom function is applied to each element, and the list is sorted accordingly.

Example : In this example code defines a function `sortSecond` that returns the second element of a tuple. It then creates a list of tuples, `list1`, and sorts it in ascending order based on the second element using the `sortSecond` function.

Output:

[(1, 1), (1, 2), (3, 3)]
[(3, 3), (1, 2), (1, 1)]

Sorting List of Strings by Length in Sort() in Python

In this method we sorts a list of strings in ascending order of their lengths using the `sort()` function with the `key=len`. This means that the strings are arranged from the shortest to the longest length in the resulting sorted list.

Example : In this example the below code defines a list of strings, words, and then sorts it based on the length of each string using the len() function as the sorting key. Finally, it prints the sorted list.

Output :

Sorted by Length: ['kiwi', 'apple', 'grape', 'banana', 'orange']

Sorting List of Tuples by a Specific Element

To sort a list of tuples by a specific element, use the `sort()` function with the `key` parameter. Specify a lambda function as the key, targeting the desired element’s index. The tuples will be sorted based on the values of that specific element.

Example : In this method code defines a list of tuples named ‘people,’ where each tuple represents a person’s name and age. It then sorts the list based on the second element of each tuple (age) using the sort method and a lambda function as the sorting key.

Output :

Sorted by Age: [('Charlie', 22), ('Alice', 25), ('David', 28), ('Bob', 30)]

Sorting List of Dictionaries by a Specific Key

This method involves using the `sort()` function on a list of dictionaries in Python. By specifying a lambda function as the key parameter, you can sort the list based on a specific key within each dictionary. This enables the list of dictionaries to be arranged in ascending order according to the values associated with the chosen key.

Example : In this example code defines a list of dictionaries called students, where each dictionary represents a student with “name” and “age” keys. It then sorts the list of dictionaries based on the “age” key in each dictionary using the sort method and a lambda function as the key.

Output :

Sorted by Age: [
    {'name': 'Charlie', 'age': 22},
    {'name': 'Alice', 'age': 25},
    {'name': 'David', 'age': 28},
    {'name': 'Bob', 'age': 30}
]

Difference between sorted() and sort() function in Python

Let us see the difference between the sorted() and sort() function in Python:

To know more please refer Python difference between the sorted() and sort() function.