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[itertools] itertools permutations example

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08-21-2021 167 words One minute 0 views

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The itertools library makes it easy to generate Perumatation from both strings and list. The code example below show all perumataiton of number pairs.

1. number pairs

import itertools

x = [1, 2, 3, 4, 5, 6]

# output all permutations of x
print(list(itertools.permutations(x, 2)))

# output
[(1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 3), (2, 4), (2, 5),
 (2, 6), (3, 1), (3, 2), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3),
 (4, 5), (4, 6), (5, 1), (5, 2), (5, 3), (5, 4), (5, 6), (6, 1), (6, 2),
 (6, 3), (6, 4), (6, 5)]

2. string permitations

import itertools

# output all permutations of the word "Two"
print(list(itertools.permutations("Two", 1)))

#ouput
[
  ('T', 'w', 'o'),
  ('T', 'o', 'w'),
  ('w', 'T', 'o'),
  ('w', 'o', 'T'),
  ('o', 'T', 'w'),
  ('o', 'w', 'T')
]

3. count possible combinations

import itertools
# just count the permutations
print(len(list(itertools.permutations("Hello"))))
print(len(list(itertools.permutations("123456789"))))

#output
120
362880

References