Is this a bug?

Terry Reedy tjreedy at udel.edu
Wed Jul 17 01:50:43 CEST 2013


On 7/16/2013 2:04 PM, Ian Kelly wrote:

> The documentation appears to be wrong.  It says:
>
> """
> If a name binding operation occurs anywhere within a code block, all
> uses of the name within the block are treated as references to the
> current block. This can lead to errors when a name is used within a
> block before it is bound. This rule is subtle. Python lacks
> declarations and allows name binding operations to occur anywhere
> within a code block. The local variables of a code block can be
> determined by scanning the entire text of the block for name binding
> operations.
> """
I agree that there is a problem.
http://bugs.python.org/issue18478

> But this only applies to function blocks, not the general case.  In
> general, I believe it is more accurate to say that a variable is local
> to the block if its name is found in the locals() dict.

That is not true for functions, where names are classified as local 
*before* being added to the locals dict. (Actually, names are usually 
not added to the locals dict until locals() is called to update it).

It would be better to say that names are local if found in the local 
namespace, and consider that names are added to a function local 
namespace (which is *not* the local() dict) when classified (before 
being bound), but otherwise only when bound.


   That normally
> won't be true until the variable has been bound.  Any references prior
> to that will look for a global variable.

At module scope, globals() == locals(). But feel free to suggest a 
different fix for the issue than I did.

-- 
Terry Jan Reedy




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