Fixed.

Tests are susceptible to input mutation.

Fixed!

missing random tests.

Does it really? I think it reassigns the binding, but doesn't change the referenced object.

I might be wrong, I don't know that much Python.

got it

There is a mistake in the description: "Thus, the expected value of a random element from the matrix is 3.". Should be "473/6" instead of "3"

fixed

There's an issue with the description. The input is defined as "Two integers r and c representing the number of rows and columns of the matrix, respectively" but, in the provided example, an input of "11 5" somehow expects the calculation of a 12x6 matrix.

It works, probably your code was similar but not the same, did you try copying and pasting it?

this code didn't work for me

This solution is forcing lowercase to account for the case-insensitive constraint. Also, your solution is being redundant by checking for a bool value to return a bool value.

Nice using of f string