[Python-ideas] A "within" keyword
steve at pearwood.info
Sat Jun 9 05:03:55 EDT 2018
On Fri, Jun 08, 2018 at 02:41:54PM -0400, David Teresi wrote:
> One of the features I miss from languages such as C# is namespaces that
> work across files - it makes it a lot easier to organize code IMO.
I too have often wanted a sub-module namespace without the need to
separate code into seperate files. Something like a package, but
existing inside a single physical file. In pseudo-code:
a = 1
# conceptually, this is like a module within a module
a = 100
spam() + A.spam()
=> returns 101
If that looks similar to the class statement, except there's no need to
create an instance, that's deliberate.
> Here's an idea I had - it might not be the best idea, just throwing this
> out there: a "within" keyword that lets you execute code inside a
> namespace. For example:
> within cool_namespace:
> def foo():
> print("foo run")
> within A.cool_namespace:
> foo() # prints "foo run"
This sort of thing is similar to a old FAQ:
so it isn't unambiguously clear what foo would mean: is it the current
namespace foo, the surrounding namespace, or the module namespace?
Its not necessarily undoable: currently Python has what the "Learning
Python" book calls the LEGB scoping rule:
L - local
E - enclosing function(s) or class
G - global (module)
B - builtins
It could be conceivable to add a rule to slot a namespace in there
somewhere, but the scoping rules already are fairly hairy (e.g. classes
and functions work a little differently, we have a sub-local scope for
comprehensions) and I'd be cautious about making them hairier with
something like your "within"/"with" statement.
The question I have is what is your motive for this? What problem does
this solve for you?
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