Python List sort() Method

The Python list.sort() method is a built-in function that is used to sort a list in ascending or descending order. By default, the sort() method sorts the elements of a list in ascending order. However, you can use the reverse parameter to sort the list in descending order.

Related: Python sorted() Function

In this article, I will explain the syntax of the Python list sort() method, its parameters and explain how to sort a list in ascending, descending, and user-defined order with examples.

1. Quick Examples of List sort() Method

If you are in a hurry, below are some quick examples of the python list sort() method.


# Below are the quick examples

# Example 1: Sort list by ascending order
technology = ['Java','Hadoop','Spark','Pandas','Pyspark','NumPy']
technology.sort()

# Example 2: Sort the list in descending order
technology.sort(reverse=True)

# Example 3: Sort a list of strings in descending order
technology = ['Java','Hadoop','Spark','Pandas','Pyspark','NumPy']
technology.sort(key=len, reverse=True)

# Example 4: Sort a list of Integers in ascending order
numbers = [5, 2, 8, 3, 6, 9]
numbers.sort()

# Example 5: Sorting using user-defined order 
def get_length(val):
  return val[1]

# Sorts the array in ascending according to
# get_length element
myList = [(2, 3), (4, 6), (1, 5)]
myList.sort(key=get_length)

# Example 6: Sorts the array in ascending according to
# get_length element
sort_list = sorted(myList, key=get_length)

2. Syntax of sort() Method

Following is the syntax for creating sort() method


# Syntax of sort()  function
list.sort(reverse=True/False, key=myFunc)

2.1 Parameter of sort()

The sort() method takes the following optional parameters.

  • key – A function that takes an element of the list as input and, a function to specify the sorting criteria(s).
  • reverse – A boolean value specifies whether the list should be sorted in ascending (False) or descending (True) order. The default is reverse=False.

3. Sort List of Strings in Ascending Order

By using the Python list sort() function let’s sort the list of strings in ascending order, For strings ascending order means it sorts in alphabetical order. The sort() method by default sorts in ascending order


# Sort the list in ascending order
technology = ['Java','Hadoop','Spark','Pandas','Pyspark','NumPy']
technology.sort()
print(technology)

# Output:
# ['Hadoop', 'Java', 'NumPy', 'Pandas', 'Pyspark', 'Spark']

4. Sort List of Strings in Descending Order

To sort a list of strings in descending order, you can use the sort() method with the reverse argument set its value to reverse=True. Descending order is the opposite of ascending order where elements are arranged from highest to lowest value.


# Sort the list of alphabets in descending order
technology = ['Java','Hadoop','Spark','Pandas','Pyspark','NumPy']
technology.sort(reverse=True)
print(technology)

# Output:
# ['Spark', 'Pyspark', 'Pandas', 'NumPy', 'Java', 'Hadoop']

5. Sort List of Strings by Length

You can pass the function to the key to sort a Python list in a custom order. For example, pass key=len to sort a list of strings by length. You can also use the reverse parameter to specify whether the sort should be in ascending or descending order. The following example sorts the list of items based on their length in descending order.


# Sort a list of strings in descending order
technology = ['Java','Hadoop','Spark','Pandas','Pyspark','NumPy']
technology.sort(key=len, reverse=True)
print(technology)

# Output:
# ['Pyspark', 'Hadoop', 'Pandas', 'Spark', 'NumPy', 'Java']

6. Sort List of Integers in Ascending & Descending Order

Let’s also see an example of sorting integers in ascending order. It is a stable sort, meaning that it preserves the original order of equal elements.


# Sort a list of Integers in ascending order
numbers = [5, 2, 8, 3, 6, 9]
numbers.sort()
print(numbers)

# Output
# [2, 3, 5, 6, 8, 9]

# Sort a list of Integers in descending order
numbers.sort(reverse=True)
print(numbers)

# Output
# [9, 8, 6, 5, 3, 2]

7. Python List Sort using User-defined Order

Alternatively, you can use the Python list sort() method to order the list by custom order. Here, I will use the get_length() function. This function is used to extract the second element of each tuple in the list, and the list is sorted in ascending order based on these values.


# Sorting using user-defined order 
def get_length(val):
  return val[1]

# Create list of tupple
myList = [(2, 3), (4, 6), (1, 5)]

# Sorts the array
myList.sort(key=get_length)
print(List)

# Using sorted() function
List = sorted(List, key=get_length)
print(List)

# Output:
# [(2, 3), (1, 5), (4, 6)]

You can call the sort() function on the list List and sorts it in descending order based on the values returned by the get_length() function. It takes a tuple val as input and returns the second element of the tuple. This element is used to determine the sort order of the list.


# Sorts the array in descending according to
# get_length element
myList.sort(key=get_length, reverse=True)
print(myList)

# Output
# [(4, 6), (1, 5), (2, 3)]

Conclusion

In this article, I have explained the Python list sort() method syntax, parameters, and how to sort the list of strings and integers in ascending and descending order, and also learned how to sort user-defined order with examples.

Happy Learning !!

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