How do I make an __eq__method to compare a class with 4 init variables?
Question:
I have the following class:
class Building():
def __init__(self, item1, item2, item3, item4):
self._item1 = item1
self._item2 = item2
self._item3 = []
self._item3.append(item3)
self._item4 = []
self._item4.append(item4)
def __eq__(self, building2):
Item1 and item2 are both int values, item3 and item4 are both lists that contain 1 item at the start with more added later possibly. How do I compare two building classes such that building1 == building2 would return true or false.
Edit: thanks for the feedback everyone, I have taken what everyone has said and changed my code it is much better now thanks!
Answers:
def __eq__(self, building2):
result1 = self.item1 == building2.item1
result2 = self.item2 == building2.item2
result3 = self.item3[0] == building2.item3[0]
result4 = self.item4[0] == building2.item4[0]
return result1 and result2 and result3 and result4
Generate two tuples and compare them:
def __eq__(self, building2):
return (self._item1, self._item2, self._item3, self._item4) == (
building2._item1, building2._item2, building3._item1, building4._item1)
You can build tuples of those attributes that you want to compare, then compare those tuples. Make sure to check if the other object is actually a Building to avoid raising an AttributeError
def __eq__(self, other):
if not isinstance(other, Building):
return False
self_attrs = (self._item1, self._item2, self._item3, self._item4)
other_attrs = (other._item1, other._item2, other._item3, other._item4)
return self_attrs == other_attrs
You can create an attribute _items in your __init__ with
self._items = self._item1, self._item2, self._item3, self._item4
and then define __eq__ as
def __eq__(self, other):
return self._items == other._items
You can use builtin vars() to compare object’s dictionaries:
class Building():
def __init__(self, item1, item2, item3, item4):
self._item1 = item1
self._item2 = item2
self._item3 = []
self._item3.append(item3)
self._item4 = []
self._item4.append(item4)
def __eq__(self, building2):
if not isinstance(building2, Building):
return False
return vars(self) == vars(building2)
b1 = Building(1, 2, 3, 4)
b2 = Building(1, 2, 3, 4)
b3 = Building(1, 2, 3, 3)
print(b1 == b2)
print(b1 == b3)
Outputs:
True
False
in eq you should use type(self) == type(other) instead of isinstance(other, self_class_name):
def __eq__(self, other):
return (type(self), vars(self)) == (type(other), vars(other))
Try to run:
class Person:
def __init__(self, name='Guido', surname='van Rossum'):
self.name = name
self.surname = surname
class Student(Person):
__slots__ = 'university'
def __init__(self, university='University of Amsterdam',**kwargs):
super().__init__(**kwargs)
self.university = university
p = Person()
s = Student()
print(isinstance(s, Person))
print(vars(p) == vars(s))
I have the following class:
class Building():
def __init__(self, item1, item2, item3, item4):
self._item1 = item1
self._item2 = item2
self._item3 = []
self._item3.append(item3)
self._item4 = []
self._item4.append(item4)
def __eq__(self, building2):
Item1 and item2 are both int values, item3 and item4 are both lists that contain 1 item at the start with more added later possibly. How do I compare two building classes such that building1 == building2 would return true or false.
Edit: thanks for the feedback everyone, I have taken what everyone has said and changed my code it is much better now thanks!
def __eq__(self, building2):
result1 = self.item1 == building2.item1
result2 = self.item2 == building2.item2
result3 = self.item3[0] == building2.item3[0]
result4 = self.item4[0] == building2.item4[0]
return result1 and result2 and result3 and result4
Generate two tuples and compare them:
def __eq__(self, building2):
return (self._item1, self._item2, self._item3, self._item4) == (
building2._item1, building2._item2, building3._item1, building4._item1)
You can build tuples of those attributes that you want to compare, then compare those tuples. Make sure to check if the other object is actually a Building to avoid raising an AttributeError
def __eq__(self, other):
if not isinstance(other, Building):
return False
self_attrs = (self._item1, self._item2, self._item3, self._item4)
other_attrs = (other._item1, other._item2, other._item3, other._item4)
return self_attrs == other_attrs
You can create an attribute _items in your __init__ with
self._items = self._item1, self._item2, self._item3, self._item4
and then define __eq__ as
def __eq__(self, other):
return self._items == other._items
You can use builtin vars() to compare object’s dictionaries:
class Building():
def __init__(self, item1, item2, item3, item4):
self._item1 = item1
self._item2 = item2
self._item3 = []
self._item3.append(item3)
self._item4 = []
self._item4.append(item4)
def __eq__(self, building2):
if not isinstance(building2, Building):
return False
return vars(self) == vars(building2)
b1 = Building(1, 2, 3, 4)
b2 = Building(1, 2, 3, 4)
b3 = Building(1, 2, 3, 3)
print(b1 == b2)
print(b1 == b3)
Outputs:
True
False
in eq you should use type(self) == type(other) instead of isinstance(other, self_class_name):
def __eq__(self, other):
return (type(self), vars(self)) == (type(other), vars(other))
Try to run:
class Person:
def __init__(self, name='Guido', surname='van Rossum'):
self.name = name
self.surname = surname
class Student(Person):
__slots__ = 'university'
def __init__(self, university='University of Amsterdam',**kwargs):
super().__init__(**kwargs)
self.university = university
p = Person()
s = Student()
print(isinstance(s, Person))
print(vars(p) == vars(s))