Python List sort() Method

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Index

1. Definition
2. Syntax
3. Parameter Values
4. Return Values
5. Key Parameter

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Definition

The sort() method sorts the items of a list in ascending or descending order.

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Syntax

The syntax of the sort() method is:

list.sort(key=..., reverse=...)

Alternatively, you can also use built-in Python sorted() Function for the same purpose.

Note

The simplest difference between sort() and sorted() is: sort() changes the list directly and doesn’t return any value, while sorted() doesn’t change the list and returns the sorted list.

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Parameter Values

Parameter	Description
iterable	Iterator objects that will be joined together
reverse (Optional)	If True, the sorted list is reversed (or sorted in descending order). Defaults to False if not provided.
key (Optional)	A function that serves as a key for the sort comparison. Defaults to None.

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Return Values

• The sort() method doesn’t return any value. Rather, it changes the original list.

• If you want a function to return the sorted list rather than change the original list, use sorted().

**Example 1) Sort a given list:

# vowels list
vowels = ['e', 'a', 'u', 'o', 'i']
 
# sort the vowels
vowels.sort()
 
# print vowels
print('Sorted list:', vowels)
# Output: Sorted list: ['a', 'e', 'i', 'o', 'u']

**Example 2) Sort in Descending order:

Setting reverse = True sorts the list in the descending order.

# vowels list
vowels = ['e', 'a', 'u', 'o', 'i']
 
# sort the vowels
vowels.sort(reverse=True)
 
# print vowels
print('Sorted list (in Descending):', vowels)
# Output: Sorted list (in Descending): ['u', 'o', 'i', 'e', 'a']

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key Parameter in Python sort()

If you want your own implementation for sorting, the sort() method also accepts a key function as an optional parameter. Example using len() function has a key parameter:

• Here, len is Python’s in-built function to count the length of an element.
• The list is sorted based on the length of each element, from lowest count to highest.

 
 
# String list
lista = ["ciao", "straordinario", "mondo"]
 
# sort list with key
lista.sort(key=len)
 
# print list
print(lista)
# Output:['ciao', 'mondo', 'straordinario']

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Particular examples

Read: Examples to see more interesting and powerful examples

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