python – How to replace element with random elements?

I want to achieve that every element in the maze is randomly chosen, but in my code, it is always either just A, B or C. What did I do wrong?

import random
new_entry = random.choice(('A ', 'B', 'C'))

def generate(size):
  y =(' ') * size
  #print(y)
  list=(' ') * size
  for i, n in enumerate(list):
    maze(i)= y
  for i in range(len(list)):
    for j in range(len(list)):
      list(i)(j)= new_entry
  print(list)

so for example I wish to get a list like this, if size=2:
list= ((A,B),(C,A))