[Python-ideas] Tweaking closures and lexical scoping to include the function being defined

[Terry Reedy]

On 9/26/2011 6:23 PM, Eric Snow wrote:

> As Terry noted, default argument values are sort of read-only.  A
> function's __defaults__ (and __kwdefaults__) is writable and bound to
> a tuple.

Oh, right, I keep forgetting that. The tuple of defaults in immutable 
but in current Python, at least, the tuple is replaceable. So a function 
can indirectly rewrite its defaults as long as it is still bound to its 
definition name.

> The local name that maps to each value in __defaults__ is
> re-initialized for each call.  The proposed nonlocal-from syntax would
> not reflect these characteristics.  Instead it is more of a
> persistent/static mechanism, just like closures.

For a default that is intended to be permanent and never overshadowed, 
there is no need to rebind with every call.

-- 
Terry Jan Reedy