Python – Itertools.Permutations()

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.

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 there position and not by there 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:-

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')

Example 2:-

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)]

Last Updated on December 29, 2021 by admin

Python – Itertools.Permutations()