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From: harrismh777 <harrismh777@charter.net>
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Subject: Re: Something is rotten in Denmark...
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Date: Tue, 31 May 2011 15:18:37 -0500
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Terry Reedy wrote:
> You have been hypnotizeed by lambda. (lambda n: i+n) is a *constant
> expression*, so you get 10 'equal' functions.


'hypnotized' indeed!  ... ok, so let me see if I get this... the lambda 
defers lookup|bind of its references until such time as the lambda is 
'called' and not at the time (as I thought) that the anonymous 
function(s) are returned?

If I'm understanding that correctly, then that means lambda is working 
as designed, and that there are very subtle nuances to be aware of. In 
my little case

    (lambda n: i + n)

    ... if the  i  goes out of scope before the anonymous function gets 
called then we have a problem... or if  i   as a reference is mutable or 
refers to a different object before the anonymous function is called 
then we have a problem?

    What I am discovering is that 'yes' I can use lambda syntactically 
where I might not be able to code a def statement; however, if I do use 
it (as in a list comprehension) then I may get unexpected results if any 
of my lambda's references go out of scope or are mutable...(?)

Question:

    What are the ramifications of making the lookup|binding happen at 
the time the anonymous function is 'returned' vs 'called'?  Has anyone 
suggested this?  Is this PEP-able....?  Are there side-effects in the 
other direction?


PS  Thanks Chris, Ian, Jussi, Thomas, Terry...  I appreciate your 
teaching and patience !



kind regards,
m harris