CODEWITHSUNDEEP
pythonpython-3.x
ShenLei
ShenLei

Reputation: 587

How to generate runtime class in python

I would like to generate a group of classes with same methods but different name attribute. Eg,

class A:
    name = '1'
    def f(self):
        print('call')

class B
    name = '2'
    def f(self):
        print('call')

class C
    name = '3'
    def f(self):
        print('call')

server.register_handler_class(A)
server.register_handler_class(B)
server.register_handler_class(C)

Values of name are loaded from xx.conf file. How to do this? Do I need metaclass or __new__?

Upvotes: 1

Views: 294

Answers (2)

Sheldore
Sheldore

Reputation: 39062

IIUC, if you pre-append your variable names by __, while executing them, the name of the class is automatically appended to the beginning of the respective variables of the classes. So while accessing the variables via Class instance, the variables will become _A__name, _B__name and _C__name. This allows you to use same names without running into problems with conflicting names. You can read my answer here. I am not sure if this is what you meant.

The same can be done for methods as well: __f

Hence you can use 

class A:
    __name = '1'
    def f(self):
        print('call')

class B
    __name = '2'
    def f(self):
        print('call')

class C
    __name = '3'
    def f(self):
        print('call')

Upvotes: 0

gmds
gmds

Reputation: 19885

No, you need type and globals:

new_class_names = ['A', 'B', 'C']

def new_class_init(self):
    print(f'{self} was called.')

for class_name in new_class_names:
    globals()[class_name] = type(class_name, (), {'__init__': new_class_init}

type can be called with three parameters: name, bases and dict to return a new class.

name is the name of the new class, bases a tuple containing all its base classes and dict a dict with key-value pairs representing the method names and actual functions to be bound as methods that the new class should have.

Then, of course, to add them programmatically to the global namespace, we can reference the global dict by calling globals.

Upvotes: 2

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