Question

Python has a magic __getattr__ method that allows custom values to be returned:

class A(object):
    def __getattr__(self, name):
        return name

B = A()
print B.foo  # 'foo'

However, calling A.foo has no similar effect, because A is not an instance.

Using metaclasses, Google App Engine raises this error on instantiation:

File "/base/python27_runtime/python27_lib/versions/1/google/appengine/ext/db/__init__.py", line 913, in __init__
key_name.__class__.__name__)
    BadKeyError: Name must be string type, not tuple

Assuming the referenced question is correctly implemented, what other ways can a magic class __getattr__ be implemented?

Answer 1

The metaclass solution should work, here is an example:

class GetAttrMeta(type):
    def __getattr__(self, name):
        return name

class A(object):
    __metaclass__ = GetAttrMeta

print A.foo  # 'foo'

Or with Python 3.x:

class GetAttrMeta(type):
    def __getattr__(self, name):
        return name

class A(object, metaclass=GetAttrMeta):
    pass

print(A.foo)  # 'foo'