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.

What issue? I don't see any unused variable. This code works for me. — giusti, Sep 14 '19 at 16:54
yeah but the 'i' variable isn't be used anywhere. That's the issue that i mean — Leonardo Sawka, Sep 15 '19 at 18:04

giusti · Accepted Answer · 2019-09-24T16:24:24.110

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.

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

1 Answers1