I am implementing a transition tables as a class attribute with,

class Phase:
    num_states = 15
    transition_table = [[False for _ in range(num_states)] for _ in range(num_states)]

but it failed with NameError: name 'num_states' is not defined.
However, 1d array works as expected,

class Phase:
    num_states = 15
    transition_table = [False for _ in range(num_states)] # this works

I was wondering why this is the case, as num_states is defined before transition_table and it should have access to the previous one?