Python program to sort a list of tuples alphabetically

Given a list of tuples, write a Python program to sort the tuples alphabetically by the first item of each tuple. Examples:

Input: [("Amana", 28), ("Zenat", 30), ("Abhishek", 29), ("Nikhil", 21), ("B", "C")]
Output: [('Amana', 28), ('Abhishek', 29), ('B', 'C'), ('Nikhil', 21), ('Zenat', 30)]

Input: [("aaaa", 28), ("aa", 30), ("bab", 29), ("bb", 21), ("csa", "C")]
Output: [('aa', 30), ('aaaa', 28), ('bab', 29), ('bb', 21), ('csa', 'C')]

Method 1: Using Bubble sort Using the technique of Bubble Sort to we can perform the sorting. Note that each tuple is an element in the given list. Access the first 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 alphabetically


# Function to sort the list of
# tuples

def SortTuple(tup):

    # Getting the length of list
    # of tuples
    n = len(tup)

    for i in range(n):
        for j in range(n-i-1):

            if tup[j][0] > tup[j + 1][0]:
                tup[j], tup[j + 1] = tup[j + 1], tup[j]

    return tup

# Driver's code

tup = [("Amana", 28), ("Zenat", 30), ("Abhishek", 29),
        ("Nikhil", 21), ("B", "C")]

print(SortTuple(tup))

Output:

[('Abhishek', 29), ('Amana', 28), ('B', 'C'), ('Nikhil', 21), ('Zenat', 30)]

Method 2: Using sort() method While sorting via this method the actual content of the tuple is changed, and just like the previous method, the in-place method of the sort is performed. 

Python3

# Python program to sort a list of
# tuples using sort()

# Function to sort the list
def SortTuple(tup):

    # reverse = None (Sorts in Ascending order)
    # key is set to sort using first element of
    # sublist lambda has been used
    tup.sort(key = lambda x: x[0])
    return tup

# Driver's code

tup = [("Amana", 28), ("Zenat", 30), ("Abhishek", 29),
        ("Nikhil", 21), ("B", "C")]

print(SortTuple(tup))

Output:

[('Abhishek', 29), ('Amana', 28), ('B', 'C'), ('Nikhil', 21), ('Zenat', 30)]

Method 3: Using sorted() method sorted() method is a method of list class that returns the sorted list without making any changes to the original list. 

Python3

# Python program to sort a list of
# tuples using sorted()

# Function to sort the list
def Sort_Tuple(tup):

    # reverse = None (Sorts in Ascending order)
    # key is set to sort using first element of
    # sublist lambda has been used
    return(sorted(tup, key = lambda x: x[0]))

# Driver Code
tup = [("Amana", 28), ("Zenat", 30), ("Abhishek", 29),
        ("Nikhil", 21), ("B", "C")]

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

Output:

[('Abhishek', 29), ('Amana', 28), ('B', 'C'), ('Nikhil', 21), ('Zenat', 30)]

Time Complexity: O(n*logn), as sorted() function is used.
Auxiliary Space: O(n), where n is length of list.