dynamic assigments

[Jean-Michel Pichavant]

Jean-Michel Pichavant wrote:
> Seldon wrote:
>> On 03/25/2011 12:05 AM, Steven D'Aprano wrote:
>>> On Thu, 24 Mar 2011 19:39:21 +0100, Seldon wrote:
>>>
>>>> Hi, I have a question about generating variable assignments 
>>>> dynamically.
>>> [...]
>>>> Now, I would like to use data contained in this list to dynamically
>>>> generate assignments of the form "var1 = value1", ecc where var1 is an
>>>> identifier equal (as a string) to the 'var1' in the list.
>>>
>>> Why on earth would you want to do that?
>>>
>>
>> Because I'm in this situation.  My current code is of the form:
>>
>> var1 = func(arg=value1, *args)
>> ..
>> varn = func(arg=valuen, *args)
>>
>> where var1,..varn are variable names I know in advance and 
>> value1,..valuen are objects known in advance, too; func is a long 
>> invocation to a factory function.  Each invocation differs only for 
>> the value of the 'arg' argument, so I have a lot of boilerplate code 
>> I'd prefer to get rid of (for readability reasons).
>>
>> I thought to refactor the code in a more declarative way, like
>>
>> assignment_list = (
>> ('var1', value1),
>> ('var2', value2),
>> .. ,
>> )
>>
>> for (variable, value) in assignment_list:
>>     locals()[variable] = func(arg=value, *args)
>>
>> My question is: what's possibly wrong with respect to this approach ?
> First thing, locals help states the following:
> "Note The contents of this dictionary should not be modified; changes 
> may not affect the values of local and free variables used by the 
> interpreter"
>
> http://docs.python.org/library/functions.html#locals
>
> Can't you use something like
>
> rootValues = { 'var1': 45, 'var2': 0, }
>
> def func2x(x):
>    return x*2
>
> def main():
>    mappedValues = {}
>    for varName in rootValues:
>        mappedValues[varName] = func2x(rootValues[varName])
>        print  mappedValues[varName]
>
> main()
>
> > 90
> > 0
>
>
> JM
could be simplified to the minmum with

rootValues = [45, 0]
anyFunc = lambda x:2x
var1, var2 = [anyFunc(value) for value in rootValues ]

JM