python - 为什么它显示 __init__ 函数应该始终不返回任何内容？

Question

class Employee:
    def __init__(self, first, last, pay):
        self.k=first
        self.p=last
        self.l=pay
        self.email=first+'.'+last+'@gmail.com'
        h= self.email
        return (h)

    def fullname(self):
        return ('{} {}'.format(self.k,self.p))

emp_1=Employee('Aditya','Shrivastava', 500000)
print(emp_1.fullname())`

异常(exception):

Traceback (most recent call last):
  File "A:/Python/Programs/main.py", line 54, in <module>
    emp_1=Employee('corey','schafer',50000)
TypeError: __init__() should return None, not 'str'

Answer 1

调用

__init__ 来设置创建的新的空白实例。它始终必须返回None。来自 object.__init__() documentation :

Because __new__() and __init__() work together in constructing objects (__new__() to create it, and __init__() to customize it), no non-None value may be returned by __init__(); doing so will cause a TypeError to be raised at runtime.

对于没有 return 语句的函数，默认返回 None；从 __init__ 中删除 return (h):

class Employee:
    def __init__(self, first, last, pay):
        self.k=first
        self.p=last
        self.l=pay
        self.email=first+'.'+last+'@gmail.com'

创建实例后即可访问email属性，无需返回。