运算符重载：比较

Python 面向对象编程

Alex Yarosh

Content Quality Analyst @ DataCamp

对象相等性

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
Python 面向对象编程

对象相等性

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
Python 面向对象编程

变量是引用

customer1 = Customer("Maryam Azar", 3000, 123)
customer2 = Customer("Maryam Azar", 3000, 123)

print(customer1)

<__main__.Customer at 0x1f8598e2e48>

print(customer2)

<__main__.Customer at 0x1f8598e2240>
Python 面向对象编程

自定义比较

import numpy as np

# 两个不同的数组，数据相同
array1 = np.array([1,2,3])
array2 = np.array([1,2,3])

array1 == array2

True
Python 面向对象编程

重载 __eq__()

class Customer:
  def __init__(self, id, name):
    self.id, self.name = id, name

  # 使用 == 时会调用
  def __eq__(self, other):

    # 调试输出
    print("__eq__() is called")

    # 若所有属性匹配则返回 True
    return (self.id == other.id) and \
           (self.name == other.name)

 

 

  • 使用 == 比较该类的两个对象时会调用 __eq__()
  • 接受两个参数：self 和 other——要比较的对象
  • 返回布尔值
Python 面向对象编程

对象的比较

# 两个相等的对象

customer1 = Customer(123, "Maryam Azar")
customer2 = Customer(123, "Maryam Azar")

customer1 == customer2

__eq__() is called
True

# 两个不相等的对象——id 不同

customer1 = Customer(123, "Maryam Azar")
customer2 = Customer(456, "Maryam Azar")

customer1 == customer2

__eq__() is called
False
Python 面向对象编程

其他比较相关方法

运算符 方法
== __eq__()
!= __ne__()
>= __ge__()
<= __le__()
> __gt__()
< __lt__()
  • __hash__()：用于将对象作为字典键或放入集合
Python 面向对象编程

Passons à la pratique !

Python 面向对象编程

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