"Cast" to int in Python 3.4

Question

I am writing some simple game in Python 3.4. I am totally new in Python. Code below:

def shapeAt(self, x, y):
    return self.board[(y * Board.BoardWidth) + x]

Throws an error:

TypeError: list indices must be integers, not float

For now I have found that this may happen when Python "thinks" that list argument is not an integer. Do you have any idea how to fix that?

Answer 1

int((y * Board.BoardWidth) + x) use int to get nearest integer towards zero.

def shapeAt(self, x, y):
    return self.board[int((y * Board.BoardWidth) + x)] # will give you floor value.

and to get floor value use math.floor(by help of m.wasowski)

math.floor((y * Board.BoardWidth) + x)

Answer 2

If x, y are numbers or strings representing number literals you can use int to cast to integer, while floating point values get floored:

>>> x = 1.5
>>> type(x)
<type 'float'>
>>> int(x)
1
>>> type(int(x))
<type 'int'>

Answer 3

This is probably because your indices are of type float where these should be ints (because you are using them as array indices). I wouldn't use int(x), I think you probably intended to pass an int (if not, use return self.board[(int(y) * Board.BoardWidth) + int(x)] of course).

You may also want to get floor value to get your index and here is how to do it:

import math

def shapeAt(self, x, y):
    return self.board[math.floor((y * Board.BoardWidth) + x)]

You can also use Python's type() function to identify type of your variables.

Answer 4

what is the type of x and y you need to check that, then convert them to integer type using int:

def shapeAt(self, x, y):
    return self.board[(int(y) * Board.BoardWidth) + int(x)]

if you want to first store them:

def shapeAt(self, x, y):
    x,y = int(x),int(y)
    return self.board[(y * Board.BoardWidth) + x]