Append list into list within a for loop

[rama27]

Hi, I would like to append lists into one list in a for loop. See my code bellow:

def triangle(n: int):
    pole = []
    seznam = []
    i = 0
    j = 0  

    while j < n :          
        while i <= j:
            a = pole.append(1)
            print(pole)  
            seznam.append(a)            
            i +=1 
        j +=1
            
    print(seznam)

####END

My output for triangle(4) is

Output:
[1]
[1, 1]
[1, 1, 1]
[1, 1, 1, 1]
[None, None, None, None]

But desired output for triangle(4) is:

Output:
[[1], [1, 1], [1, 1, 1], [1, 1, 1, 1]]

Can you help me, how can I replace "None" with lists of 1? Thank you very much!