Dynamically create class attributes

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You could do it without metaclasses using decorators. This way is a bit more clear IMO:

def apply_defaults(cls):
    defaults = {
        'default_value1':True,
        'default_value2':True,
        'default_value3':True,
    }
    for name, value in defaults.items():
        setattr(cls, name, some_complex_init_function(value, ...))
    return cls

@apply_defaults
class Settings(object):
    pass

Prior to Python 2.6 class decorators were unavailable. So you can write:

class Settings(object):
    pass
Settings = apply_defaults(Settings)

in older versions of python.

In the provided example apply_defaults is reusable… Well, except that the defaults are hard-coded in the decorator’s body 🙂 If you have just a single case you can even simplify your code to this:

defaults = {
    'default_value1':True,
    'default_value2':True,
    'default_value3':True,
}

class Settings(object):
    """Your implementation goes here as usual"""

for name, value in defaults.items():
    setattr(Settings, name, some_complex_init_function(value, ...))

This is possible since classes (in the sense of types) are objects themselves in Python.

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