Python program to Sort a List of Tuples in Increasing Order by the Last Element in Each Tuple

The task is to write a Python Program to sort a list of tuples in increasing order by the last element in each tuple.

Input: [(1, 3), (3, 2), (2, 1)]
Output: [(2, 1), (3, 2), (1, 3)]
Explanation: sort tuple based on the last digit of each tuple.

Methods #1: Using sorted().

Sorted() method sorts a list and always returns a list with the elements in a sorted manner, without modifying the original sequence.

Approach:

• Take a list of tuples from the user.
• Define a function that returns the last element of each tuple in the list of tuples.
• Define another function with the previous function as the key and sort the list.
• Print the sorted list.

Python3

def last(n):
    return n[-1]

def sort(tuples):
    return sorted(tuples, key=last)

a=[(1, 3), (3, 2), (2, 1)]
print("Sorted:")
print(sort(a))

Output:

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

Methods #2: Using Bubble Sort.

Access the last element of each tuple using the nested loops. This performs the in-place method of sorting. The time complexity is similar to the Bubble Sort i.e. O(n^2).

Python3

# Python program to sort
# a list of tuples by the second Item

# Function to sort the list
# of tuples by its second item
def Sort_Tuple(tup):

    # getting length of list of tuples
    lst = len(tup)
    for i in range(0, lst):

        for j in range(0, lst-i-1):
            if (tup[j][-1] > tup[j + 1][-1]):
                temp = tup[j]
                tup[j]= tup[j + 1]
                tup[j + 1]= temp
    return tup

# Driver Code
tup =[(1, 3), (3, 2), (2, 1)]

print(Sort_Tuple(tup))

Output:

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

Methods #3: Using sort().

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

Python3

# Python program to sort a list of
# tuples by the second Item using sort()

# Function to sort the list by second item of tuple
def Sort_Tuple(tup):

    # reverse = None (Sorts in Ascending order)
    # key is set to sort using second element of
    # sublist lambda has been used
    tup.sort(key = lambda x: x[-1])
    return tup

# Driver Code
tup = [(1, 3), (3, 2), (2, 1)]

# printing the sorted list of tuples
print(Sort_Tuple(tup))

Output:

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