I have this matrix:
mat = [[ 0 for x in range(row)] for y in range(column)]
I tried to add elements to the matrix:
for x in range(row): # row is 2
for y in range(column): # column is 3
mat[x][y] = int(input("number: "))
but the shell returns this error:
Traceback (most recent call last):
File "C:\Users\Fr\Desktop\pr.py", line 13, in <module>
mat[x][y] = 12
IndexError: list assignment index out of range
how do I add elements to a matrix?
The inner list should be based on columns:
mat = [[ 0 for x in range(column)] for y in range(row)]
Here is an example:
In [73]: row = 3
In [74]: column = 4
In [78]: mat = [[ 0 for x in range(column)] for y in range(row)]
In [79]:
In [79]: for x in range(row): # row is 2
for y in range(column): # column is 3
mat[x][y] = 5
....:
In [80]: mat
Out[80]: [[5, 5, 5, 5], [5, 5, 5, 5], [5, 5, 5, 5]]
mat = [[0]*column for y in range(row)]; it's also a bit faster & more compact. OTOH, I guess doing it the long way is easier that explaining why [[0]*column]*row is not safe. :)I think it should be:
>>> for x in range(column):
... for y in range(row):
... mat[x][y] = int("number: ")
...
1
2
3
4
5
6
>>> mat
[[1, 2], [3, 4], [5, 6]]
mat is considered falsely created. The matrix initially=empty is in this form: [[0, 0], [0, 0], [0, 0]] or at least that is what the OP creates ...