[Python-Dev] constant/enum type in stdlib

[Michael Foord]

On 25/11/2010 10:12, Nadeem Vawda wrote:
> On Thu, Nov 25, 2010 at 11:34 AM, Glenn Linderman<v+python at g.nevcal.com>  wrote:
>> So the following code defines constants with associated names that get put
>> in the repr.
> The code you gave doesn't work if the constant() function is moved
> into a separate module from the code that calls it.  The globals()
> function, as I understand it, gives you access to the global namespace
> *of the current module*, so the constants end up being defined in the
> module containing constant(), not the module you're calling it from.
>
> You could get around this by passing the globals of the calling module
> to constant(), but I think it's cleaner to use a class to provide a
> distinct namespace for the constants.
>
>> An idea I had, but have no idea how to implement, is that it might be nice
>> to say:
>>
>>      with imported_constants_from_module:
>>             do_stuff
>>
>> where do_stuff could reference the constants without qualifying them by
>> module.  Of course, if you knew it was just a module of constants, you could
>> "import * from module" :)  But the idea of with is that they'd go away at
>> the end of that scope.
> I don't think this is possible - the context manager protocol doesn't
> allow you to modify the namespace of the caller like that.  Also, a
> with statement does not have its own namespace; any names defined
> inside its body will continue to be visible in the containing scope.
>
> Of course, if you want to achieve something similar (at function
> scope), you could say:
>
> def foo(bar, baz):
>      from module import *
>      ...

Not in Python 3 you can't. :-)

That's invalid syntax, import * can only be used at module level. This 
makes *testing* import * (i.e. testing your __all__) annoying - you have 
to exec('from module import *') instead.

Michael

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