# Python | Custom length Matrix

• Last Updated : 30 Dec, 2020

Sometimes, we need to initialize a matrix in Python of variable length from the list containing elements. In this article, we will discuss the variable length method initialization and certain shorthands to do so. Let’s discuss certain ways to perform this.

Method #1 : Using `zip()` + list comprehension
The zip function combined with the list comprehension can help to achieve this particular task. The zip function can help to zip the counter list with the element list and list comprehension does the work of construction of matrix.

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 `# Python3 code to demonstrate  ``# Custom length Matrix ``# using zip() + list comprehension`` ` `# initializing list``test_list ``=` `[``'a'``, ``'b'``, ``'c'``]`` ` `# initializing counter list ``counter_list ``=` `[``1``, ``4``, ``2``]`` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `# printing counter list ``print` `(``"The counter list is : "` `+` `str``(counter_list))`` ` `# using zip() + list comprehension``# Custom length Matrix ``res ``=` `[[i] ``*` `j ``for` `i, j ``in` `zip``(test_list, counter_list)]`` ` `# printing result``print` `(``"The custom length matrix is : "` `+` `str``(res))`
Output :

```The original list is : ['a', 'b', 'c']
The counter list is : [1, 4, 2]
The custom length matrix is : [['a'], ['b', 'b', 'b', 'b'], ['c', 'c']]
```

Method #2 : Using `map() + mul operator`
This particular problem can also be solved using the inbuilt mul operator which performs multiplication of liked index elements and map function performs the task of formation of matrix.

 `# Python3 code to demonstrate  ``# Custom length Matrix ``# using map() + mul operator``from` `operator ``import` `mul`` ` `# initializing list``test_list ``=` `[``'a'``, ``'b'``, ``'c'``]`` ` `# initializing counter list ``counter_list ``=` `[``1``, ``4``, ``2``]`` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `# printing counter list ``print` `(``"The counter list is : "` `+` `str``(counter_list))`` ` `# using map() + mul operator``# Custom length Matrix ``res ``=` `list``(``map``(mul, [[``'a'``], [``'b'``], [``'c'``]], counter_list))`` ` `# printing result``print` `(``"The custom length matrix is : "` `+` `str``(res))`
Output :
```The original list is : ['a', 'b', 'c']
The counter list is : [1, 4, 2]
The custom length matrix is : [['a'], ['b', 'b', 'b', 'b'], ['c', 'c']]
```

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