Python | Sort Tuples in Increasing Order by any key

Given a tuple, sort the list of tuples in increasing order by any key in tuple. Examples:

Input : tuple = [(2, 5), (1, 2), (4, 4), (2, 3)] 
            m = 0
Output : [(1, 2), (2, 3), (2, 5), (4, 4)]
Explanation: Sorted using the 0th index key.

Input :  [(23, 45, 20), (25, 44, 39), (89, 40, 23)]
         m = 2
Output : Sorted: [(23, 45, 20), (89, 40, 23), (25, 44, 39)] 
Explanation: Sorted using the 2nd index key

Given tuples, we need to sort them according to any given key. This can be done using sorted() function where we sort them using key=last and store last as the key index according to which we have to sort the given tuples. Below is the Python implementation of the above approach:

Python

# Python code to sort a list of tuples
# according to given key.

# get the last key.
def last(n):
    return n[m]

# function to sort the tuple
def sort(tuples):

    # We pass used defined function last
    # as a parameter.
    return sorted(tuples, key = last)

# driver code
a = [(23, 45, 20), (25, 44, 39), (89, 40, 23)]
m = 2
print("Sorted:"),
print(sort(a))

Output:

Sorted: [(23, 45, 20), (89, 40, 23), (25, 44, 39)] 

Another  approach  is  using the operator.itemgetter() function from the operator module. The itemgetter() function returns a callable object that can be used to retrieve an item from an object, such as a tuple.

Here is an example of how to use itemgetter() to sort a list of tuples by any key:

Python3

import operator

def sort_tuples(tuples, key):
    return sorted(tuples, key=operator.itemgetter(key))

tuples = [(2, 5), (1, 2), (4, 4), (2, 3)]
key = 0
print(sort_tuples(tuples, key))  # Output: [(1, 2), (2, 3), (2, 5), (4, 4)]

Output

[(1, 2), (2, 5), (2, 3), (4, 4)]

This approach has the advantage of being concise and efficient, as it uses the built-in sorted() function and the itemgetter() function from the operator module. It is also easy to understand and implement.

Note that the itemgetter() function returns a callable object that can be used to retrieve an item from an object, such as a tuple. To sort the tuples, we pass this callable object to the key argument of the `sorted

Approach#3: Using lambda

One way to sort tuples in increasing order by any key is to use the sorted function and pass a key function that returns the desired element of each tuple.

Algorithm

1. Define a key function that returns the desired element of each tuple.
2. Use the sorted function to sort the list of tuples using the key function.

Python3

def sort_tuples(tuples, key_idx):
    # Step 1: Define a key function that returns the desired element of each tuple.
    key_func = lambda x: x[key_idx]

    # Step 2: Use the `sorted` function to sort the list of tuples using the key function.
    sorted_tuples = sorted(tuples, key=key_func)

    return sorted_tuples

# Example usage:
tuples = [(2, 5), (1, 2), (4, 4), (2, 3)]
sorted_tuples = sort_tuples(tuples, 0)
print(sorted_tuples)

tuples = [(23, 45, 20), (25, 44, 39), (89, 40, 23)]
sorted_tuples = sort_tuples(tuples, 2)
print(sorted_tuples)

Output

[(1, 2), (2, 5), (2, 3), (4, 4)]
[(23, 45, 20), (89, 40, 23), (25, 44, 39)]

Time Complexity: O(n log n), where n is the number of tuples in the list. This is because sorting takes O(n log n) time in the worst case.
Space Complexity: O(n), where n is the number of tuples in the list. This is because we create a new sorted list of tuples.