The list.sort() method in Python is used to sort the elements of a list in ascending order by default. This method modifies the original list in place and does not return a new list.

Syntax

list.sort(key=None, reverse=False)

• Parameters:
  • key (optional): A function that serves as a key for the sorting comparison. This function takes a single argument and returns a value to be used for sorting.
  • reverse (optional): A boolean value. If set to True, the list elements are sorted in descending order. The default is False, meaning the elements are sorted in ascending order.

Return Value

• The method does not return a value (None is returned implicitly) and modifies the original list.

Example Usage

1. Sorting a List in Ascending Order:

   my_list = [3, 1, 4, 1, 5, 9]
   my_list.sort()  # Sorts the list in ascending order
   print(my_list)  # Output: [1, 1, 3, 4, 5, 9]
   

2. Sorting a List in Descending Order: You can sort in descending order by setting the reverse parameter to True:

   my_list = [3, 1, 4, 1, 5, 9]
   my_list.sort(reverse=True)  # Sorts the list in descending order
   print(my_list)  # Output: [9, 5, 4, 3, 1, 1]
   

3. Sorting a List of Strings: The sort() method can also be used with lists of strings:

   fruits = ['banana', 'apple', 'cherry']
   fruits.sort()  # Sorts the list in ascending order (alphabetically)
   print(fruits)  # Output: ['apple', 'banana', 'cherry']
   

4. Using the Key Parameter: You can use the key parameter to sort the list based on specific criteria. For example, sorting a list of tuples based on the second element:

   my_list = [(1, 'one'), (3, 'three'), (2, 'two')]
   my_list.sort(key=lambda x: x[1])  # Sorts based on the second element of each tuple
   print(my_list)  # Output: [(1, 'one'), (3, 'three'), (2, 'two')]
   

5. Sorting a List of Mixed Data Types: The sort() method raises a TypeError if you try to sort a list containing mixed data types that are not directly comparable:

   mixed_list = [1, 'banana', 3.14]
   try:
       mixed_list.sort()  # Attempting to sort mixed types
   except TypeError as e:
       print(e)  # Output: '<' not supported between instances of 'str' and 'int'
   

6. Sorting with Custom Logic: You can create complex sorting logic using the key parameter. For example, sorting a list of strings by their length:

   words = ['banana', 'apple', 'kiwi', 'cherry']
   words.sort(key=len)  # Sorts based on the length of each word
   print(words)  # Output: ['kiwi', 'apple', 'banana', 'cherry']
   

Summary

• list.sort(key=None, reverse=False) is a powerful method for sorting lists in Python.
• It modifies the original list in place and does not return a new list.
• The optional key parameter allows for custom sorting criteria, and the reverse parameter enables descending order sorting.
• It's essential to ensure that the list contains comparable elements; otherwise, a TypeError will occur.