Re: Statement local namespaces summary (was Re: python3: 'where' keyword)

[Andrey Tatarinov]

Nick Coghlan wrote:
Nick Coghlan wrote:
Semantics
---------
The code::
<statement> with:
   <suite>
translates to::
def unique_name():
    <suite>
    <statement>
unique_name()
I've come to the conclusion that these semantics aren't what I would 
expect from the construct. Exactly what I would expect can't really be 
expressed in current Python due to the way local name bindings work. The 
main thing to consider is what one would expect the following to print:

def f():
    a = 1
    b = 2
    print 1, locals()
    print 3, locals() using:
        a = 2
        c = 3
        print 2, locals()
    print 4, locals()
I think the least suprising result would be:
1 {'a': 1, 'b': 2}         # Outer scope
2 {'a': 2, 'c': 3}         # Inner scope
3 {'a': 2, 'b': 2, 'c': 3} # Bridging scope
4 {'a': 1, 'b': 2}         # Outer scope
as for me, I would expect following:
1 {'a': 1, 'b': 2}
2 {'a': 2, 'b': 2, 'c': 3'}
3 {'a': 2, 'b': 2, 'c': 3'}
4 {'a': 1, 'b': 2}
otherwise that would be impossible to do calculations based on scope 
variables and "using:" would be useless =), consider example of usage:

current_position = 1
current_environment # = ...
current_a_lot_of_other_parameters # = ...
scores = [count_score(move) for move in aviable_moves] using:
        def count_score(move):
                #walking through current_environment
                return score
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