Replacing globals in exec by custom class

[DevPlayer]

Couple of things:

I don't think this is what you want:

   def __getitem__(self, key):
        import __builtin__
        if key == 'xx':
            return 'xx'
I won't return a KeyError for any string you give g[]
It will return 'xx' only if you supply key='xx' and ignore every other
key=???
With the above code you can do g['yyy'] and you would get None

For your example code to work, line 14 in your example needs to be:
elif key in self.__dict__: # (change else to elif)

for your dict (or globalscl) to act like other dicts() add
an else:
	raise KeyError( 'Key not found: %s' % (key,))

__dict__ of a dict I believe is not the namespace of dict. I thought
dict[key] and dict.__dict__[key] where not the same place

__dict__ of dict in Python 2.5 and prior was rumored to be buggy and
unused. Don't know about Python 2.6 +

I thought __getitem__() did not look in __dict__ of dict().

If I copy your code into a module globalcl.py
and comment out "print xx" in the string,
and in PyCrust I "import globalcl"
I too get the results and errors you claim.

If I then do:

>>>globalcl.g.keys()
I get: ['__builtins__']

>>>globalcl.g['__builtins__']
I get: nothing (or None)

>>>globalcl.g['__builtin__']
I get: nothing (or None)

# -------------------------
# interesting part

>>>globalcl.g['xx']
I get: 'xx'

>>>if 'xx' in globalcl.g:
...    print True
...else:
...    print False

I get: False
# -------------------------

>>>globalcl.g.__builtins__
AttributeError: 'Global' object has no attribute  __builtins__'

>>>globalcl.g.__builtins__
AttributeError: 'Global' object has no attribute '__builtin__'

>>>globalcl.g.__dict__
{'q': <function q at 0x01C738B0>}