How to return a value from __init__ in Python? How to return a value from __init__ in Python? python python

How to return a value from __init__ in Python?


python class init

Why would you want to do that?

If you want to return some other object when a class is called, then use the __new__() method:

class MyClass(object):    def __init__(self):        print "never called in this case"    def __new__(cls):        return 42obj = MyClass()print obj

python class init

__init__ is required to return None. You cannot (or at least shouldn't) return something else.

Try making whatever you want to return an instance variable (or function).

>>> class Foo:...     def __init__(self):...         return 42... >>> foo = Foo()Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: __init__() should return None

python class init

From the documentation of __init__:

As a special constraint on constructors, no value may be returned; doing so will cause a TypeError to be raised at runtime.

As a proof, this code:

class Foo(object):    def __init__(self):        return 2f = Foo()

Gives this error:

Traceback (most recent call last):  File "test_init.py", line 5, in <module>    f = Foo()TypeError: __init__() should return None, not 'int'

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