i've a local variable unused in a function that made a matrix

Question

I've a local variable that's not used in a function. This function does a matrix and returns that matrix empty.

I've tried to use 'i' variable using an "if i is None: pass" but the issue continue.

def create_matrix(rows, columns):
    matrix = [[None] * columns for i in range(rows)]
    return matrix

i want to dismiss this issue. Is there any way to do it? I know it's a stupid problem but i'm a little bit obsessed with have my code fully clean.

Answer 1

There's no issue if you never use an iterator variable. i in your code behaves like an iterator in a for that is not used:

for (int i = 0; i < 10; i++)
  // do something without using i

This would be ok in any language like C, C++, PHP...

However, if you really don't want named variables that are not used in any expression, you call it _:

def create_matrix(rows, columns):
    matrix = [[None] * columns for _ in range(rows)]
    return matrix

The _ variable is a implicit variable. It always exists, so you are not declaring anything new. It always has the value of the last evaluated expression and may be used in fors like that.