Question

I’m trying to override globals so that any attribute name
that doesn’t exists returns itself(the name string).
The reason for this is to use it in eval to do some quick/hacky parsing of a c initilizer list, (and just because of course).
My Code:

class EvalGlobalsDict(dict):
    def __getattr__(self, name):
        if hasattr(self, name):
            return super(EvalGlobalsDict, self).__getattr__(name) 
        else:
            return name


eval_globals = EvalGlobalsDict(globals())

Whenever I try to eval a non existent name it gives me a NameError

eval("aaa",eval_globals)

And if I try to directly call

eval("globals().__getattr__("dir")",eval_globals)
eval("globals().__getattr__("dir")",eval_globals)

I only get back the attr name string even for valid attributtes.
What am I doing wrong?

Answer 1

Since you’re subclassing a dict, you’ll want to override __getitem__ (the indexing accessor).

class EvalGlobalsDict(dict):
    def __getitem__(self, name):
        return self.get(name, name)

foo = 1337
eval_globals = EvalGlobalsDict(globals())
print repr(eval("aaa", eval_globals))
print repr(eval("foo", eval_globals))

prints

> 'aaa'
> 1337