I recently start teaching myself game programming. Someone recommend me to start with Python and I got the book "Beginning game development with Python and Pygame: From novice to professional". I got to a part where they teach about Vectors and creating a Vector2 class. Everything was going well until I tried to overload the division operator. My code goes like this:
class Vector2(object):
def __init__(self, x=0.0, y=0.0):
self.x = x
self.y = y
def __str__(self):
return "(%s, %s)"%(self.x, self.y)
@classmethod
def from_points(cls, P1, P2):
return cls(P2[0] - P1[0], P2[1] - P1[1])
def __add__(self,rhs):
return Vector2(self.x + rhs.x, self.y + rhs.y)
def __sub__(self,rhs):
return Vector2(self.x - rhs.x, self.y - rhs.y)
def __mul__(self, scalar):
return Vector2( self.x*scalar, self.y*scalar)
def __div__(self, scalar):
return Vector2( self.x/scalar, self.y/scalar)
Now, when I tried to call the "/" operator, this shows up:
AB = Vector2(10.0,25.0)
print(AB) # <<<<(10.0, 25.0)
v1 = AB + Vector2(20.,10.)
print(v1) # <<<<(30.0, 35.0)
v2 = AB - Vector2(20.,10.)
print(v2) # <<<<(-10.0, 15.0)
v3 = AB * 3
print(v3) # <<<<(30.0, 75.0)
print(v3 / 3)
TypeError: unsupported operand type(s) for /: 'Vector2' and 'int'
This was all in Python 3.3 but if I run it with Python 2.7, everything works correctly. Where's the problem?
In Python 3.x, you need to overload the __floordiv__
and __truediv__
operators, not the __div__
operator. The former corresponds to the //
operation (returns an integer) and the latter to /
(returns a float).