How to rotate a matrix (2D array) by 90 degrees using zip?

In line 4, you write an integer to the variable "a":

a=random.randint(-5,4)

Then, in line 9, you try to access the variable "a" by index.

a[i]=int(a[i])

But integer variables don't support indexing. To make it work, you need to replace line 4 with this:

a.append(random.randint(-5,4))

In general, your code is not very Pythonic. Where possible, it's recommended to use list comprehensions instead of loops. They are much more concise, and the code with them becomes