Operator overloading: comparison
Object-Oriented Programming in Python
Alex Yarosh
Content Quality Analyst @ DataCamp
Object equality
class Customer: def __init__(self, name, balance): self.name, self.balance = name, balance customer1 = Customer("Maryam Azar", 3000) customer2 = Customer("Maryam Azar", 3000)customer1 == customer2
False
Object equality
class Customer:
def __init__(self, name, balance, id):
self.name, self.balance = name, balance
self.id = id
customer1 = Customer("Maryam Azar", 3000, 123)
customer2 = Customer("Maryam Azar", 3000, 123)
customer1 == customer2
False
Variables are references
customer1 = Customer("Maryam Azar", 3000, 123)
customer2 = Customer("Maryam Azar", 3000, 123)
print(customer1)
<__main__.Customer at 0x1f8598e2e48>
print(customer2)
<__main__.Customer at 0x1f8598e2240>
Custom comparison
import numpy as np
# Two different arrays containing the same data
array1 = np.array([1,2,3])
array2 = np.array([1,2,3])
array1 == array2
True
Overloading __eq__()
class Customer: def __init__(self, id, name): self.id, self.name = id, name# Will be called when == is used def __eq__(self, other):# Diagnostic printout print("__eq__() is called") # Returns True if all attributes match return (self.id == other.id) and \ (self.name == other.name)
__eq__()is called when 2 objects of a class are compared using==- accepts 2 arguments,
selfandother- objects to compare - returns a Boolean
Comparison of objects
# Two equal objects
customer1 = Customer(123, "Maryam Azar")
customer2 = Customer(123, "Maryam Azar")
customer1 == customer2
__eq__() is called
True
# Two unequal objects - different ids
customer1 = Customer(123, "Maryam Azar")
customer2 = Customer(456, "Maryam Azar")
customer1 == customer2
__eq__() is called
False
Other comparison operators
| Operator | Method |
|---|---|
== |
__eq__() |
!= |
__ne__() |
>= |
__ge__() |
<= |
__le__() |
> |
__gt__() |
< |
__lt__() |
__hash__()to use objects as dictionary keys and in sets
Let's practice!
Object-Oriented Programming in Python
