Python | Pair and combine nested list to tuple list

Difficulty Level : Expert
Last Updated : 02 Apr, 2019

Sometimes we need to convert between the data types, primarily due to the reason of feeding them to some function or output. This article solves a very particular problem of pairing like indices in list of lists and then construction of list of tuples of those pairs. Let’s discuss how to achieve the solution of this problem.

Method #1 : Using zip() + list comprehension
We can use zip function to link to each element’s like indices and list comprehension can be used to perform the logic behind the conversion to tuple and extending the logic to all the sublists.

# Python3 code to demonstrate
# Pairing and combining nested list to tuple list
# using zip() + list comprehension
  
# initializing lists 
test_list1 = [[1, 4, 5], [8, 7], [2]]
test_list2 = [['g', 'f', 'g'], ['f', 'r'], ['u']]
  
# printing original lists
print("The original list 1 : " + str(test_list1))
print("The original list 2 : " + str(test_list2))
  
# using zip() + list comprehension
# Pairing and combining nested list to tuple list
res = [(u, v) for x, y in zip(test_list1, test_list2)
                               for u, v in zip(x, y)]
  
# print result
print("The paired list of tuple is : " + str(res))

Output :

The original list 1 : [[1, 4, 5], [8, 7], [2]]
The original list 2 : [[‘g’, ‘f’, ‘g’], [‘f’, ‘r’], [‘u’]]
The paired list of tuple is : [(1, ‘g’), (4, ‘f’), (5, ‘g’), (8, ‘f’), (7, ‘r’), (2, ‘u’)]

Method #2 : Using zip() + itertools.chain.from_iterable()
This problem can also be solved using the zip function along with the from_iterable function. The task performed by zip function remains the same but conversion to tuple and do it for all elements can be handled by from_iterable function.

# Python3 code to demonstrate
# Pairing and combining nested list to tuple list
# using zip() + itertools.chain.from_iterable()
from itertools import chain
  
# initializing lists 
test_list1 = [[1, 4, 5], [8, 7], [2]]
test_list2 = [['g', 'f', 'g'], ['f', 'r'], ['u']]
  
# printing original lists
print("The original list 1 : " + str(test_list1))
print("The original list 2 : " + str(test_list2))
  
# using zip() + itertools.chain.from_iterable()
# Pairing and combining nested list to tuple list
res = list(zip(chain.from_iterable(test_list1),
             chain.from_iterable(test_list2)))
  
# print result
print("The paired list of tuple is : " + str(res))

Output :

The original list 1 : [[1, 4, 5], [8, 7], [2]]
The original list 2 : [[‘g’, ‘f’, ‘g’], [‘f’, ‘r’], [‘u’]]
The paired list of tuple is : [(1, ‘g’), (4, ‘f’), (5, ‘g’), (8, ‘f’), (7, ‘r’), (2, ‘u’)]

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