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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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