yield, curry, mix-in, new.function, global, closure, .... what will work?

ecir.hana at gmail.com ecir.hana at gmail.com
Sun Apr 15 19:24:08 CEST 2007

Dear list,

maybe I'm overlooking something obvious or this is not possible at all
or I don't know. Please, consider the following code:

## insert here anything you like

def changer():

def run(i='', j=''):

    ## insert here anything you like

    return i, j

run() == 'changed_i', 'changed_j'

Let me explain: First, changer() is kind of templating language so it
should be written down in this form - however, it can change during
run-time as you like. Basically, it is just ordinary python code which
changes (should change) the local variables of another function,
run(). Oh, and it has to be *thread-safe*.

Here's what I tried and didn't work (maybe I just haven't tried hard
- pass i, j around: changer(i, j) and change_i(i, arg) - easiest, most
obvious solution - can't do it, certainly not during writing of the
code - have to preserve changer()'s form
- global variable - not thread-safe
- in run(), create dummy closure for changer() and call it -
new.function(blah, blah, blah, dummy.func_closure) - not thread safe,
i guess, and besides change_i() and change_j() would also need a such
a trick - I am not sure how to  alter the codeobject of changer()
- new.function(new.code(... - oh my, this won't work
- in run(), modify change_i() and change_j() so it actually yield-s
the changes, collect them here - something like: change_i.__call__  =
return yield ('changed_i', 'comes_from_changer_i()') - doesn't work,
of course
- update locals() - yes!! - no!! - doen't work, it's just a copy
- curry, mix-in, ... - hmm....
- eval(blah, blah, locals()) - not safe, ugly - maybe? what do you
- find out which file changer() is written in, which line it starts
and ends, read that file's section, parse, edit, append the needed
local variable's declarations, compile to changer_new() and changer =
changer_new - there has to be something better! :)

So, to wrap up, the question is: how can I pass a variable from one
function to another, without writing down function's argument during
coding, and still be thread-safe?

I can only hope you are still with me and not very confused....

Thanks for any feedback!!

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