# Python – K Matrix Initialization

• Last Updated : 30 Dec, 2020

Sometimes in the world of competitive programming, we need to initialise the matrix, but we don’t wish to do it in a longer way using a loop. We need a shorthand for this. This type of problem is quite common in dynamic programming domain. Let’s discuss certain ways in which this can be done.

Method #1 : Using List comprehension
List comprehension can be treated as a shorthand for performing this particular operation. In list comprehension, we can initialise the inner list with K and then extend this logic to each row again using the list comprehension.

 `# Python3 code to demonstrate ``# K Matrix Initialization ``# using list comprehension`` ` `# Declaring rows``N ``=` `5`` ` `# Declaring columns``M ``=` `4`` ` `# initializing K ``K ``=` `7`` ` `# using list comprehension ``# to initializing matrix``res ``=` `[ [ K ``for` `i ``in` `range``(N) ] ``for` `j ``in` `range``(M) ]`` ` `# printing result ``print``(``"The matrix after initializing with K : "` `+` `str``(res))`

Output :

```The matrix after initializing with K : [[7, 7, 7, 7, 7], [7, 7, 7, 7, 7], [7, 7, 7, 7, 7], [7, 7, 7, 7, 7]]
```

Method #2 : Using list comprehension + “*” operator
This problem can also be simplified using the * operator which can slightly reduce the tedious way task is done and can simply use multiply operator to extent the initialization to all N rows.

 `# Python3 code to demonstrate ``# K Matrix Initialization ``# using list comprehension``# and * operator`` ` `# Declaring rows``N ``=` `5`` ` `# Declaring columns``M ``=` `4`` ` `# initializing K``K ``=` `7`` ` `# using list comprehension ``# to initializing matrix``res ``=` `[ [K ``for` `i ``in` `range``(M)] ``*` `N]`` ` `# printing result ``print``(``"The matrix after initializing with K : "` `+` `str``(res))`

Output :

```The matrix after initializing with K : [[7, 7, 7, 7, 7], [7, 7, 7, 7, 7], [7, 7, 7, 7, 7], [7, 7, 7, 7, 7]]
```

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