__div__ is a function that takes two arguments, a numerator and denominator. The problem is that it can produce incorrect results when dividing two numbers that are not both integers.
def __div__(self, other): return self.value / other.value
This is a Python method definition. It is defining a method called __div__ that takes two arguments, self and other. The method will return the result of self.value divided by other.value.
In Python, the truediv function returns the true division (integer division) of two integers.
In Python, the floor() function returns the lowest integer value not greater than the argument.