Transpose Dual Tuple List in Python

Sometimes, while working with Python tuples, we can have a problem in which we need to perform tuple transpose of elements i.e, each column element of dual tuple becomes a row, a 2*N Tuple becomes N * 2 Tuple List. This kind of problem can have possible applications in domains such as web development and day-day programming. Let's discuss certain ways in which this task can be performed.

Input : test_list = [(2, 'Gfg'), (3, 'is'), (94, 'Best')]
Output : ([2, 3, 94], ['Gfg', 'is', 'Best'])
Input : test_list = [(8, 1)]
Output : ([8, 1])

Method #1: Using loop

This is one of the ways in which this problem can be solved. In this, we employ a brute force strategy to perform the transpose by constructing 2 lists and combining them to get the transposed results.

# Python3 code to demonstrate working of 
# Transpose Tuple List
# Using loop

# hlper_fnc function
def hlper_fnc(test_list):
    # declare empty list
    sub1 = []
    sub2 = []

    res = (sub1, sub2)
    for sub in test_list:
        # add element in the last of the list
        sub1.append(sub[0])
        sub2.append(sub[1])

    return res

# initializing list
test_list = [(5, 1), (3, 4), (9, 7), (10, 6)]

# printing original list
print("The original list is : " + str(test_list))

# Transpose Tuple List
# Using loop
res = hlper_fnc(test_list)

# printing result 
print("The transposed tuple list : " + str(res)) 

Output: 
 

The original list is : [(5, 1), (3, 4), (9, 7), (10, 6)]
The transposed tuple list : ([5, 3, 9, 10], [1, 4, 7, 6])

Time complexity: O(N), where N is the length of the input list. This is because the program iterates through each element of the input list once in the for loop.
Auxiliary space: O(N), where N is the length of the input list. This is because the program creates two new lists, sub1 and sub2, each of size N, to store the transposed elements of the input list.

Method #2 : Using loop + zip() + tuple()

The combination of above functionalities can also be used to solve this problem. In this, we perform the task of forming transpose and extract columnar elements using zip().

# Python3 code to demonstrate working of 
# Transpose Tuple List
# Using zip() + tuple()

# hlper_fnc function
def hlper_fnc(test_list):
    return tuple(zip(*test_list))

# initializing list
test_list = [(5, 1), (3, 4), (9, 7), (10, 6)]

# printing original list
print("The original list is : " + str(test_list))

# Transpose Tuple List
# Using zip() + tuple()
sub1, sub2 = hlper_fnc(test_list) 
res = (list(sub1), list(sub2))

# printing result 
print("The transposed tuple list : " + str(res)) 

Output: 
 

The original list is : [(5, 1), (3, 4), (9, 7), (10, 6)]
The transposed tuple list : ([5, 3, 9, 10], [1, 4, 7, 6]

Time complexity: O(n), where n is the number of tuples in the input list. 
Auxiliary space: O(n), where n is the number of tuples in the input list.

Method #3: Using the numpy library:

Step-by-step approach:

• Import the numpy library.
• Define the list of tuples to transpose.
• Convert the list of tuples to a numpy array using np.array().
• Use the transpose() function to transpose the array.
• Convert the transposed array back to a list of tuples using a list comprehension.
• Print the original list and the transposed tuple list.

import numpy as np
# initializing list
test_list = [(5, 1), (3, 4), (9, 7), (10, 6)]
arr = np.array(test_list)
res = arr.transpose()
# printing original list
print("The original list is : " + str(test_list))
# printing result
print("The transposed tuple list : " + str([tuple(x) for x in res]))
#This code is contributed by Jyothi Pinjala.

Output:

The original list is : [(5, 1), (3, 4), (9, 7), (10, 6)]
The transposed tuple list : [(5, 3, 9, 10), (1, 4, 7, 6)]

Time complexity: O(n^2), where n is the length of the input list of tuples.
Auxiliary Space: O(n), where n is the length of the input list of tuples. 

Method #4: Using list comprehension and map() function

Step-by-step approach:

• A list of tuples called "test_list" is defined with 4 tuples containing 2 elements each.
• The "map" function is used in combination with a list comprehension to transpose the "test_list" by using the "zip" function to group together the first elements of each tuple, and the second elements of each tuple, respectively. This results in a new list of 2 tuples, each containing 4 elements.
• The "list" function is used to convert the result of the "map" function into a list, and this list is stored in the variable "transposed_list".
• The original "test_list" and the transposed "transposed_list" are printed to the console using the "print" function and string concatenation. The original list is printed by converting it to a string using the "str" function.

# defining the input list of tuples
test_list = [(5, 1), (3, 4), (9, 7), (10, 6)]

# transposing the tuple list using list comprehension and map() function
transposed_list = list(map(list, zip(*test_list)))

# printing the original and transposed tuple lists
print("The original list is: " + str(test_list))
print("The transposed tuple list is: " + str(transposed_list))

The original list is: [(5, 1), (3, 4), (9, 7), (10, 6)]
The transposed tuple list is: [[5, 3, 9, 10], [1, 4, 7, 6]]

Time complexity: O(n^2) due to the nested iteration of zip() and map(). 
Auxiliary space: O(n) for the transposed list that is created.

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Article Tags :

• Python
• Python list-programs

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• python