Python implements type checking of instance attributes-Python Tutorial-php.cn

Python implements type checking of instance attributes

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Release： 2018-03-29 14:13:00

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This article mainly introduces in detail how Python performs type checking on instance attributes. It has certain reference value. Interested friends can refer to it. I hope it can help you.

Case:

In a certain project, we implemented some classes and hoped to type-check their instance properties like static languages

p = Person()

p.name = 'xi_xi' # Must be str

p.age = 18 # Must be int

p.height = 1.75 # Must be float

Requirements:

You can specify the type for the instance variable name

Giving an incorrect type throws an exception

#!/usr/bin/python3
 
 
class Attr(object):
 """
 对Person类中属性进行类型检查
 """
 # 传入字段名字 + 指定字段类型
 def __init__(self, name, style):
  self.name = name
  self.style = style
  
 # 取值
 def __get__(self, instance, owner):
  return instance.__dict__[self.name]
  
 # 设值
 def __set__(self, instance, value):
  # 判断参数类型是否满足条件
  if isinstance(value, self.style):
   instance.__dict__[self.name] = value
  else:
   raise TypeError(&#39;need type: %s&#39; % self.style)
  
 # 删除值
 def __delete__(self, instance):
  del instance.__dict__[self.name]
 
 
class Person(object):
 name = Attr(&#39;name&#39;, str)
 age = Attr(&#39;age&#39;, int)
 height = Attr(&#39;height&#39;, float)
  
 
if __name__ == &#39;__main__&#39;:
 p = Person()
  
 p.name = &#39;xi_xi&#39;
 # p.name = 55
 p.age = 18
 p.height = 1.75
 print(p.name, p.age, p.height)
  
 del p.height

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