Permutation is an arrangement of objects in a specific order. Order of arrangement of object is very important. The number of permutations on a set of n elements is given by n!. For example, there are 2! = 2*1 = 2 permutations of {1, 2}, namely {1, 2} and {2, 1}, and 3! = 3*2*1 = 6 permutations of {1, 2, 3}, namely {1, 2, 3}, {1, 3, 2}, {2, 1, 3}, {2, 3, 1}, {3, 1, 2} and {3, 2, 1}.

# Python function to print permutations of a given list
def permutation(lst):
# If lst is empty then there are no permutations
if len(lst) == 0:
return []
# If there is only one element in lst then, only
# one permuatation is possible
if len(lst) == 1:
return [lst]
# Find the permutations for lst if there are
# more than 1 characters
l = [] # empty list that will store current permutation
# Iterate the input(lst) and calculate the permutation
for i in range(len(lst)):
m = lst[i]
# Extract lst[i] or m from the list. remLst is
# remaining list
remLst = lst[:i] + lst[i+1:]
# Generating all permutations where m is first
# element
for p in permutation(remLst):
l.append([m] + p)
return l
# Driver program to test above function
data = list('123')
for p in permutation(data):
print p |

Output:

['1', '2', '3']
['1', '3', '2']
['2', '1', '3']
['2', '3', '1']
['3', '1', '2']
['3', '2', '1']