Let's say I have a class Circle with the following definition:
class Circle:
def __init__(self, r, _id):
self.r = r
self.id = _id
def area(self):
return math.pi * (self.r ** 2)
I want to write a function that compares two circles and returns the id of the smallest one
def compare_circles(circle_1: Circle, circle_2: Circle) -> str:
if circle_1.r < circle_2.r:
return circle_1.id
else:
return circle_2.id
I would like to place this method as a static method on the class. (Is this a bad idea?)
class Circle:
def __init__(self, r, _id):
self.r = r
self.id = _id
def area(self):
return math.pi * (self.r ** 2)
@staticmethod
def compare_circles(circle_1: Circle, circle_2: Circle) -> str:
if circle_1.r < circle_2.r:
return circle_1.id
else:
return circle_2.id
However this does not work because the Circle object is not available to be type hinted. I have to remove the type hints in the method. Using a classmethod also does not work, as the cls argument is not available to the other method arguments.
A possible workaround in this case would be to monkey-patch the method after defining the class:
class Circle:
def __init__(self, r, _id):
self.r = r
self.id = _id
def area(self):
return math.pi * (self.r ** 2)
def compare_circles(circle_1: Circle, circle_2: Circle) -> str:
if circle_1.r < circle_2.r:
return circle_1.id
else:
return circle_2.id
Circle.compare_circles = staticmethod(compare_circles)
del compare_circles
The usual way would be to provide a string with the type name:
class Circle:
def __init__(self, r, _id):
self.r = r
self.id = _id
def area(self):
return math.pi * (self.r ** 2)
@staticmethod
def compare_circles(circle_1: 'Circle', circle_2: 'Circle') -> str:
if circle_1.r < circle_2.r:
return circle_1.id
else:
return circle_2.id
As an aside, you might also consider turning compare_circles into a method:
def compare(self, other: 'Circle') -> str:
if self.r < other.r:
return self.id
else:
return other.id