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Python – Itertools.Permutations()

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  • Difficulty Level : Basic
  • Last Updated : 26 Aug, 2022
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Itertool is a module provided by Python for creating iterators for efficient looping. It also provides various features or functions that work with iterators to produce complex iterators and help us to solve problems easily and efficiently in terms of time as well as memory. Itertools module provides us various ways to manipulate the sequence that we are traversing through. 

Different types of iterators provided by this module are:

Note: For more information, refer to Python Itertools

Itertools.permutation()

Itertools.permutation() function falls under the Combinatoric Generators. The recursive generators that are used to simplify combinatorial constructs such as permutations, combinations, and Cartesian products are called combinatoric iterators. As understood by the word “Permutation” it refers to all the possible combinations in which a set or string can be ordered or arranged. Similarly here itertool.permutations() method provides us with all the possible arrangements that can be there for an iterator and all elements are assumed to be unique on the basis of their position and not by their value or category. All these permutations are provided in lexicographical order. The function itertool.permutations() takes an iterator and ‘r’ (length of permutation needed) as input and assumes ‘r’ as default length of iterator if not mentioned and returns all possible permutations of length ‘r’ each. Syntax:

Permutations(iterator, r)

Example 1:- 

Python3




from itertools import permutations
 
 
a = "GeEK"
 
# no length entered so default length
# taken as 4(the length of string GeEK)
p = permutations(a)
 
# Print the obtained permutations
for j in list(p):
  print(j)

Output :-

('G', 'e', 'E', 'K')
('G', 'e', 'K', 'E')
('G', 'E', 'e', 'K')
('G', 'E', 'K', 'e')
('G', 'K', 'e', 'E')
('G', 'K', 'E', 'e')
('e', 'G', 'E', 'K')
('e', 'G', 'K', 'E')
('e', 'E', 'G', 'K')
('e', 'E', 'K', 'G')
('e', 'K', 'G', 'E')
('e', 'K', 'E', 'G')
('E', 'G', 'e', 'K')
('E', 'G', 'K', 'e')
('E', 'e', 'G', 'K')
('E', 'e', 'K', 'G')
('E', 'K', 'G', 'e')
('E', 'K', 'e', 'G')
('K', 'G', 'e', 'E')
('K', 'G', 'E', 'e')
('K', 'e', 'G', 'E')
('K', 'e', 'E', 'G')
('K', 'E', 'G', 'e')
('K', 'E', 'e', 'G')

Time Complexity: O(n!) where n is the size of the string.
Auxiliary Space: O(n*n!) 

Example 2:- 

Python3




from itertools import permutations
   
print ("All the permutations of the given list is:")
print (list(permutations([1, 'geeks'], 2)))
print()
 
print ("All the permutations of the given string is:")
print (list(permutations('AB')))
print()
   
print ("All the permutations of the given container is:")
print(list(permutations(range(3), 2)))

Output:-

All the permutations of the given list is:
[(1, 'geeks'), ('geeks', 1)]

All the permutations of the given string is:
[('A', 'B'), ('B', 'A')]

All the permutations of the given container is:
[(0, 1), (0, 2), (1, 0), (1, 2), (2, 0), (2, 1)]

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