Basic python, NxN matrix printing the terms being the sum of the term coordinates in the matrix-CodePudding

Hy guys, i'm new to python, i'm trying to make an NxN matrix, that print out a matrix that have the terms value's being the sum of the coordinates of it.

In this example i used N=5

    N = 5
    M = []
    linha = []
    for i in range (N):
      linha.append(0)
    for i in range(N):
      M.append(linha)
    print(f"{M}") # just to make sure it's printing the NxN matrix
    for i in range(N):
      for j in range(N):
        M[i][j] = i   j
    print(M) #returning the final matrix

I'm getting this:

[[4, 5, 6, 7, 8],

[4, 5, 6, 7, 8],

[4, 5, 6, 7, 8]]

While i was expecting:

[[0, 1, 2, 3, 4],

[1, 2, 3, 4, 5],

[2, 3, 4, 5, 6],

[3, 4, 5, 6, 7],

[4, 5, 6, 7, 8]]

Since, for example, the first term is the M[0][0], so 0 0=0

Sorry if i wrote things that may be not too clear, but that's my problem, if anyone can help i would appreciate!

CodePudding user response：

A concise way of getting the desired result, using a nested list comprehension:

N = 5
M = [[i j for j in range(N)] for i in range(N)]
print(M)

CodePudding user response：

Like what was said in a comment:

The code for i in range(N): M.append(linha) means that M[0], M[1] ...M[N] are all references to the same object linha. So after that, when you change (for example) M[1][0], you're changing element 0 of the same object which all the rows of your matrix contain.

This means you're always referencing the same variable. You could make a small change to your code, so the new list of zeroes is created independent of name using a list comprehension:

N = 5
M = []
for i in range(N):
    M.append([0 for i in range(N)])
print(f"{M}")

for i in range(N):
    for j in range(N):
        M[i][j] = i   j
print(M) #returning the final matrix