On Thu, 13 Jan 2005 22:41:54 +0300, Andrey Tatarinov <[EMAIL PROTECTED]> wrote:
>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}
locals() doesn't automatically show everything that is visible from its local
scope:
>>> def foo():
... a = 1
... b = 2
... print 1, locals()
... def inner():
... a = 2
... c = 3
... print 2, locals()
... inner()
... print 4, locals()
...
>>> foo()
1 {'a': 1, 'b': 2}
2 {'a': 2, 'c': 3}
4 {'a': 1, 'b': 2, 'inner': <function inner at 0x02EE8BFC>}
-- unless you actually use it (this is a bit weird maybe?):
>>> def foo():
... a = 1
... b = 2
... print 1, locals()
... def inner():
... a = 2
... c = 3
... print 2, locals(), 'and b:', b
... inner()
... print 4, locals()
...
>>> foo()
1 {'a': 1, 'b': 2}
2 {'a': 2, 'c': 3, 'b': 2} and b: 2
4 {'a': 1, 'b': 2, 'inner': <function inner at 0x02EE8D4C>}
of course a difference using the new syntax is that 'inner' is not bound to a
persistent name.
>
>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
No worry, UIAM.
Regards,
Bengt Richter
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