Python | Swap tuple elements in list of tuples

While doing competitive programming, one can come across a question in which one requires to work with 2D plane and work with coordinates. One such subproblem can be swapping x, y coordinate elements. Let’s discuss certain ways in which this problem can be solved using tuple element swapping.

Method #1 : Using list comprehension
This is just a brute method to perform the longer method of loop for swapping the elements. In this a new list of tuple is created rather than an inplace swap.

# Python3 code to demonstrate working of 
# Swap tuple elements in list of tuples 
# Using list comprehension 
  
# initializing list 
test_list = [(3, 4), (6, 5), (7, 8)] 
  
# printing original list 
print("The original list is : " + str(test_list)) 
  
# Swap tuple elements in list of tuples 
# Using list comprehension 
res = [(sub[1], sub[0]) for sub in test_list] 
          
# printing result 
print("The swapped tuple list is : " + str(res)) 

Output :

The original list is : [(3, 4), (6, 5), (7, 8)]
The swapped tuple list is : [(4, 3), (5, 6), (8, 7)]

Method #2 : Using map() + lambda
Yet another way to perform this task is using map and lambda. This is a bit slower in execution but a more compact way to perform this task.

# Python3 code to demonstrate working of 
# Swap tuple elements in list of tuples 
# Using map() + lambda 
  
# initializing list 
test_list = [(3, 4), (6, 5), (7, 8)] 
  
# printing original list 
print("The original list is : " + str(test_list)) 
  
# Swap tuple elements in list of tuples 
# Using map() + lambda 
res = list(map(lambda sub: (sub[1], sub[0]), test_list)) 
          
# printing result 
print("The swapped tuple list is : " + str(res)) 

Output :

The original list is : [(3, 4), (6, 5), (7, 8)]
The swapped tuple list is : [(4, 3), (5, 6), (8, 7)]

My Personal Notes

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