__builtins__

[Marc 'BlackJack' Rintsch]

On Fri, 08 Feb 2008 00:25:14 -0800, loquehumaine wrote:

> I have seen that if I type help() at a prompt, and then 'modules',
> I'll be given a list of all modules available, thanks to this group..
> But I have seen the differences between them and the one in
> dir(__builtins__).
> Why are some modules in __builtins__ and others don't ? (UserDict for
> example)

`__builtins__` doesn't contain modules::

 Python 2.4.4 (#2, Apr 12 2007, 21:03:11)
 [GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)] on linux2
 Type "help", "copyright", "credits" or "license" for more information.
 >>> import inspect
 >>> inspect.getmembers(__builtins__, inspect.ismodule)
 []

> Why dir(__builtins__) gives me "math" but not help(__builtins__) ?

So there's no 'math' in `__builtins__`::

 >>> 'math' in dir(__builtins__)
 False

> What are the differences between __builtins__ and __builtin__ ? (By
> the way, I have python 2.4)

`__builtins__` is an implementation detail, and `__builtin__` is a name
of a module you can import.  You should not use `__builtins__` but import
`__builtin__` and inspect that instead of `__builtins__`.

The (symmetric) difference of the two is empty::

 >>> import __builtin__
 >>> set(dir(__builtins__)).symmetric_difference(dir(__builtin__))
 set([])

> Finally, if I do del(__builtins__), what can I do to repair the
> "mistake" (as I got an import error __import__ not found if I want to
> import __builtins__...?

Don't ``del __builtins__`` in the first place.  :-)

> That's may be obvious for you, but that's all strange to me and I
> didn't find answers on the net...

So the real question is, why you see 'math' in `__builtins__`.  It should
not be there.

Ciao,
	Marc 'BlackJack' Rintsch