python list permutation code example
Example 1: all permutations python
import itertools
print(list(itertools.permutations([1,2,3])))
Example 2: python permutation
import itertools
a = [1, 2, 3]
n = 3
perm_iterator = itertools.permutations(a, n)
for item in perm_iterator:
print(item)
Example 3: python permutation list
def permutations(iterable, r=None):
pool = tuple(iterable)
n = len(pool)
r = n if r is None else r
if r > n:
return
indices = list(range(n))
cycles = list(range(n, n-r, -1))
yield tuple(pool[i] for i in indices[:r])
while n:
for i in reversed(range(r)):
cycles[i] -= 1
if cycles[i] == 0:
indices[i:] = indices[i+1:] + indices[i:i+1]
cycles[i] = n - i
else:
j = cycles[i]
indices[i], indices[-j] = indices[-j], indices[i]
yield tuple(pool[i] for i in indices[:r])
break
else:
return
print ( list(permutations([1, 2, 3], 2)) )