Python: Why randint on a matrix keeps giving me the same rows [duplicate]

I'm using Python 3 and with this code:

import randommat = [[0]*5]*5for i in range (0,5) :    for j in range (0,5)  :        mat[i][j] = random.randint(10,50)print (mat)

I'm getting results like this:

[[26, 10, 28, 21, 15], [26, 10, 28, 21, 15], [26, 10, 28, 21, 15], [26, 10, 28, 21, 15], [26, 10, 28, 21, 15]]

The rows are equal each other, but the loop seems to be alright.

What is the problem?