Satish ML wrote:
> Hi,
>
> TypeError: 'NoneType' object is not callable? Why this error and what is
> the solution? Code:
> class SuperMeta:
> def __call__(self, classname, supers, classdict):
> print('In SuperMeta.call: ', classname, supers, classdict,
> sep='\n...') Class = self.__New__(classname, supers, classdict)
> self.__Init__(Class, classname, supers, classdict)
> class SubMeta(SuperMeta):
> def __New__(self, classname, supers, classdict):
> print('In SubMeta.new: ', classname, supers, classdict,
> sep='\n...') return type(classname, supers, classdict)
> def __Init__(self, Class, classname, supers, classdict):
> print('In SubMeta init:', classname, supers, classdict,
> sep='\n...') print('...init class object:',
> list(Class.__dict__.keys()))
> class Eggs:
> pass
> print('making class')
> class Spam(Eggs, metaclass=SubMeta()):
> data = 1
> def meth(self, arg):
> pass
> print('making instance')
> X = Spam()
>
> print('data:', X.data)
> Output:
> making class
> In SuperMeta.call:
> ...Spam
> ...(<class '__main__.Eggs'>,)
> ...{'meth': <function Spam.meth at 0x0000000003539EA0>, '__module__':
> '__main__', '__qualname__': 'Spam', 'data': 1} In SubMeta.new:
> ...Spam
> ...(<class '__main__.Eggs'>,)
> ...{'meth': <function Spam.meth at 0x0000000003539EA0>, '__module__':
> '__main__', '__qualname__': 'Spam', 'data': 1} In SubMeta init:
> ...Spam
> ...(<class '__main__.Eggs'>,)
> ...{'meth': <function Spam.meth at 0x0000000003539EA0>, '__module__':
> '__main__', '__qualname__': 'Spam', 'data': 1} ...init class object:
> ['meth', '__module__', 'data', '__doc__'] making instance
> Traceback (most recent call last):
> File "C:/Users/Satish/Desktop/Python/Metaclasses7.py", line 21, in
> <module>
> X = Spam()
> TypeError: 'NoneType' object is not callable
As I have no idea what you are up to I can only list some adjustments you
probably need to make:
- __init__() and __new__() are spelt in lowercase.
- do not instantiate the metaclass:
class Spam(Eggs, metaclass=SubMeta):
...
- The metaclasses of Spam and Eggs must share a common base.
This can be achieved with
class SuperMeta(type):
...
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