Generate All Permutations of a List in Python
Hassan Saeed
Dec 10, 2020
Oct 17, 2020
Python
Python List
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Use
itertools.permutationsto Generate All Permutations of a List in Python - Use Recursion to Generate All Permutations of a List in Python
This tutorial discusses methods to generate all permutations of a list in Python.
Use itertools.permutations to Generate All Permutations of a List in Python
Python provides a standard library tool to generate permutations: itertools.permutation. The below example shows how to use this to generate all permutations of a list.
import itertools
inp_list = [4, 5, 6]
permutations = list(itertools.permutations(inp_list))
print(permutations)
Output:
[(4, 5, 6), (4, 6, 5), (5, 4, 6), (5, 6, 4), (6, 4, 5), (6, 5, 4)]
The default length of the permutation is set to be the length of the input list. However, we can specify the length of the permutation in the itertools.permutations function call. The below example illustrates this.
import itertools
inp_list = [1, 2, 3]
permutations = list(itertools.permutations(inp_list, r=2))
print(permutations)
Output:
[(4, 5), (4, 6), (5, 4), (5, 6), (6, 4), (6, 5)]
The below example illustrates how to generate all permutations of all possible lengths of a given list.
import itertools
inp_list = [1, 2, 3]
permutations = []
for i in range(1,len(inp_list)+1):
permutations.extend(list(itertools.permutations(inp_list, r=i)))
print(permutations)
Output:
[(4,), (5,), (6,), (4, 5), (4, 6), (5, 4), (5, 6), (6, 4), (6, 5), (4, 5, 6), (4, 6, 5), (5, 4, 6), (5, 6, 4), (6, 4, 5), (6, 5, 4)]
Use Recursion to Generate All Permutations of a List in Python
We can also use recursion to generate all permutations of a list in Python. The below example illustrates this.
def permutations(start, end=[]):
if len(start) == 0:
print(end)
else:
for i in range(len(start)):
permutations(start[:i] + start[i+1:], end + start[i:i+1])
permutations([4,5,6])
Output:
[4, 5, 6]
[4, 6, 5]
[5, 4, 6]
[5, 6, 4]
[6, 4, 5]
[6, 5, 4]
