Why can't I print this matrix?

Question

https://code.sololearn.com/ce11gJR42wrr/?ref=app

Answer 1

use print() to print something

M=[[1,2,3],[4,5,6],[7,8,9]]
print(M)

Answer 2

do as @Orb_H suggested, only writing the variable name works on Python console, not when you save your code in a file to execute it later (as for what sololearn do, and in fact, every constructed project, as small as it can be, do).