How to dynamically generate a nested class in Python?

Question

I have well know class and I need to dynamically generate some nested classes for the well known class.

How do I accomplish this?


def AddNestedClasses(cls):
    inner1  = type("Inner")
    # How do I inject the class 'Inner' into 'cls'?
    return cls

@AddNestedClasses
class Outer:
    pass

How about setattr(cls, 'Inner', inner1)? By the way, type("Inner") is always the class str - is that what you intended? — kaya3
– kaya3, Commented Jan 28, 2020 at 22:00
You could also do it using inheritance instead of a decorator. — kaya3
– kaya3, Commented Jan 28, 2020 at 22:01
What do you mean by a "well known" class? What would be a "not well known" class? — mkrieger1
– mkrieger1, Commented Jan 28, 2020 at 22:04
Thank you, that works. I changed the parameter passed to type to type("Inner", (), {}) to stop getting a string. And then I set the property 'Inner' as suggested above to 'inner1' and that worked. I dir the class and it has a nested class "Inner". — Daniel V.
– Daniel V., Commented Jan 28, 2020 at 22:11

Daniel V. · Accepted Answer · 2020-01-28 22:15:19Z

2

def AddNestedClasses(cls):
    inner1  = type("Inner", (), {})
    cls.Inner = inner1
    return cls

@AddNestedClasses
class Outer:
    pass

print(dir(Outer))

answered Jan 28, 2020 at 22:15

Daniel V.

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