En Tue, 25 Mar 2008 17:17:16 -0300, j vickroy <[EMAIL PROTECTED]>
escribió:
> Arnaud Delobelle wrote:
>> On Mar 25, 6:13 pm, j vickroy <[EMAIL PROTECTED]> wrote:
>>> Hello,
>>>
>>> Here is some pseudo-code that hopefully illustrates what I want to do:
>>>
>>> records = list(...)
>>> for record in records:
>>> new_fcn = define_a function_for(record)
>>> instance = my_new_class_instance()
>>> setattr(instance, 'myfcn', new_fcn)
>>> instance.execute() # instance.execute() calls instance.myfcn(*args)
>>>
>>> I have looked at some of the functions in the *new* module and
>>> new.code(...), new.function(...), and new.instancemethod(...) appear to
>>> do what I want, but I do not know how to use new.code() and
>>> new.function() -- specifically what its *global* parameter should be.
>>
>> The best way to understand how new.function and new.code work is to
>> look at the Python source. (Objects/funcobject.c and Objects/
>> codeobject.c, actual objects are defined in and Include/funcobject.h
>> Include/code.h).
>>
>> However, to create a function dynamically in Python it is often no
>> more trouble than a def statement:
>
> As per your suggestion, I tried looking at include/code.h and
> include/funcobject.h (my MS Windows distribution does not appear to
> contain .c files). However, since I'm not a C programmer, I did not
> find the .h files all that helpful.
It's not really necesary to look at the source - just define the desired
function in Python.
> What I failed to make clear in my original posting is that the functions
> must be created dynamically using information in a *record* as the code
> iterates over all *records*. So, I can not pre-define the functions and
> then simply select the desired one at run-time.
It doesn't matter *how* you define the function. It may use the record
argument too. See this silly and contrived example:
def define_a function_for(record):
if hasattr(record, 'foo'):
def function_float(self, arg1, arg2):
return arg1*float(record.foo) + arg2
def function_str(self, arg1, arg2):
return arg1+arg2+len(record.foo)
if isinstance(record.foo, str):
return function_str
else:
return function_float
elif hasattr(record, 'bar') and isinstance(record.bar,basestring):
def function(self, arg1, arg2):
return self.other(record.bar.index(arg1)) - record.bar.index(arg2)
return function
else:
def function(self, *args):
return 0
return function
Plug this into your "framework" above and it should work. You don't have
to use new.*
--
Gabriel Genellina
--
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