Computing permutations is always a necessary task in many of the practical applications and a concept widely used in Mathematics to achieve solutions to many practical problems. Lets discuss certain ways in which one can perform the task of getting all the permutations of N lists.
Method #1 : Using list comprehension
List comprehension can be used to convert the naive method task into a single line, hence more compact. This method checks for each element available elements and makes pairs accordingly.
# Python3 code to demonstrate # to compute all possible permutations # using list comprehension # initializing lists list1 = [ 1 , 3 , 4 ] list2 = [ 6 , 7 , 9 ] list3 = [ 8 , 10 , 5 ] # printing lists print ( "The original lists are : " + str (list1) + " " + str (list2) + " " + str (list3)) # using list comprehension # to compute all possible permutations res = [[i, j, k] for i in list1 for j in list2 for k in list3] # printing result print ( "All possible permutations are : " + str (res)) |
Output :
The original lists are : [1, 3, 4] [6, 7, 9] [8, 10, 5]
All possible permutations are : [[1, 6, 8], [1, 6, 10], [1, 6, 5], [1, 7, 8], [1, 7, 10], [1, 7, 5], [1, 9, 8], [1, 9, 10], [1, 9, 5], [3, 6, 8], [3, 6, 10], [3, 6, 5], [3, 7, 8], [3, 7, 10], [3, 7, 5], [3, 9, 8], [3, 9, 10], [3, 9, 5], [4, 6, 8], [4, 6, 10], [4, 6, 5], [4, 7, 8], [4, 7, 10], [4, 7, 5], [4, 9, 8], [4, 9, 10], [4, 9, 5]]
Method #2 : Using itertools.product()
Using product function, one can easily perform this task in more pythonic and concise manner. This is most recommended method to perform this task of computing cartesian product.
# Python3 code to demonstrate # to compute all possible permutations # using itertools.product() import itertools # initializing list of list all_list = [[ 1 , 3 , 4 ], [ 6 , 7 , 9 ], [ 8 , 10 , 5 ] ] # printing lists print ( "The original lists are : " + str (all_list)) # using itertools.product() # to compute all possible permutations res = list (itertools.product( * all_list)) # printing result print ( "All possible permutations are : " + str (res)) |
Output :
The original lists are : [[1, 3, 4], [6, 7, 9], [8, 10, 5]]
All possible permutations are : [(1, 6, 8), (1, 6, 10), (1, 6, 5), (1, 7, 8), (1, 7, 10), (1, 7, 5), (1, 9, 8), (1, 9, 10), (1, 9, 5), (3, 6, 8), (3, 6, 10), (3, 6, 5), (3, 7, 8), (3, 7, 10), (3, 7, 5), (3, 9, 8), (3, 9, 10), (3, 9, 5), (4, 6, 8), (4, 6, 10), (4, 6, 5), (4, 7, 8), (4, 7, 10), (4, 7, 5), (4, 9, 8), (4, 9, 10), (4, 9, 5)]
Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.
To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course.