[Python] List manipulation in Python (matrix as a list of list) [duplicate]

I want to define a function called "create_matrix" that first creates an l1+1 by l2+1 matrix of zeros (implemented as a list of list; NOT numpy). Next, the function should set the first row to be [0, 1, 2, ..., l2], and the first column to be [0, 1, 2, ..., l1].

However, running the function create_matrix(7,8) returns the following matrix (see picture), which is not expected. Could you please tell me why?



def create_matrix(l1, l2):
matrix = [[0]*(l2+1)]*(l1+1)
matrix[0] = [i for i in range(0,l1+2)]
counter = 0
for inner_list in matrix:
inner_list[0] = counter
counter += 1
return matrix
create_matrix(7,8)

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