python - Matrix, index out of range -

i've declared matrix following code:

matrix = [[' ' x in range(x1)] x in range(y1)] 

but when try find random element , change it's value following code:

randomx = random.randint(0, x) randomy = random.randint(0, y) if matrix[randomx][randomy] == ' ':     try:         matrix[randomx][randomy] = 'g'         scr.addstr(randomx, randomy, matrix[randomx][randomy])         scr.refresh()     except indexerror:         return 

i indexerror. tried write garbage code exit function if runs in indexerror. works once, still throws error.

note, x1 same x in function. same goes y1 , y.

any clue i'm doing wrong?

your indices in wrong order. should access them by

matrix[randomy][randomx] 

or change order in comprehension.

matrix = [[' ' y in range(y1)] x in range(x1)] 

also, garrett pointed out in comments, randint() inclusive on both ends might want use randint(0,x-1) , randint(0,y-1).