"""
Magic method __sub__ is called when a "-" is used on any object.
Given example shows what I mean: print(some_object - other_object)
This may give error often, so that means given objects don't have __sub__ method
"""
class Test:
def __init__(self, x):
self.x = x
def __sub__(self, other):
"""
self represents the object that is first and other is object after
"-" sign. What I say here is that I expect to have attribute "x"
in both objects and I will try to subtract them. This SHOULD BE
used for objects of the same type.
"""
return self.x - other.x
t = Test(5)
t2 = Test(2) # Now I can use subtraction.
print(t - t2) # 3, without __sub__ the object doesn't understand the "-" sign.