# Python | Custom Multiplication in list of lists

• Last Updated : 25 Apr, 2019

Sometimes, when we are fed with the list of list, we need to multiply each of its element list with a particular element fed by the order in the other list. This particular problem is very specific but knowledge of it can be useful in such cases. Let’s discuss certain ways in which this can be done.

Method #1 : Using loops

This is the Naive and brute force method perform this particular task in which we run a loop to get all the elements and it’s nested components and multiply accordingly.

 `# Python3 code to demonstrate``# Custom Multiplication in list of lists``# Using loops`` ` `# initializing list``test_list ``=` `[[``5``, ``6``, ``8``], [``7``, ``4``, ``3``], [``8``, ``10``, ``12``]]`` ` `# initializing multiply list ``mult_list ``=` `[``10``, ``20``, ``30``]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# printing multiply list``print``(``"The original multiply list : "` `+` `str``(mult_list))`` ` `# using loops``# Custom Multiplication in list of lists``res ``=` `[[] ``for` `idx ``in` `range``(``len``(test_list))]``for` `i ``in` `range``(``len``(test_list)):``    ``for` `j ``in` `range``(``len``(mult_list)):``        ``res[i] ``+``=` `[mult_list[i] ``*` `test_list[i][j]]`` ` `# print result``print``(``"The list after multiply : "` `+` `str``(res))`

Output :

```The original list : [[5, 6, 8], [7, 4, 3], [8, 10, 12]]
The original multiply list : [10, 20, 30]
The list after multiply : [[50, 60, 80], [140, 80, 60], [240, 300, 360]]
```

Method #2 : Using list comprehension + `enumerate()`

This problem can also be solved in a shorter way using the power of `enumerate `function to get the indices and value of the container at one time. This is one-liner approach to solve this problem.

 `# Python3 code to demonstrate``# Custom Multiplication in list of lists``# Using list comprehension + enumerate()`` ` `# initializing list``test_list ``=` `[[``5``, ``6``, ``8``], [``7``, ``4``, ``3``], [``8``, ``10``, ``12``]]`` ` `# initializing multiply list ``mult_list ``=` `[``10``, ``20``, ``30``]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# printing multiply list``print``(``"The original multiply list : "` `+` `str``(mult_list))`` ` `# using list comprehension + enumerate()``# Custom Multiplication in list of lists``res ``=` `[[mult_list[i] ``*` `j ``for` `j ``in` `sub] ``       ``for` `i, sub ``in` `enumerate``(test_list)]`` ` `# print result``print``(``"The list after multiply : "` `+` `str``(res))`

Output :

```The original list : [[5, 6, 8], [7, 4, 3], [8, 10, 12]]
The original multiply list : [10, 20, 30]
The list after multiply : [[50, 60, 80], [140, 80, 60], [240, 300, 360]]
```

My Personal Notes arrow_drop_up