list - Creating a 2d matrix in python

Question

I create a 6x5 2d array, initially with just None in each cell. I then read a file and replace the Nones with data as I read them. I create the empty array first because the data is in an undefined order in the file I'm reading. My first attempt I did this:

x = [[None]*5]*6

which resulted in some weird errors that I now understand is because the * operator on lists may create references instead of copies.

Is there an easy one liner to create this empty array? I could just do some for loops and build it up, but that seems needlessly verbose for python.

Answer 1

Using nested comprehension lists :

x = [[None for _ in range(5)] for _ in range(6)]