Is it possible to determine what a function needs for parameters -

[Chris Mellon]

On 2 May 2007 07:22:07 -0700, rh0dium <steven.klass at gmail.com> wrote:
> Hi all,
>
> Below is a basic threading program. The basic I idea is that I have a
> function which needs to be run using a queue of data.  Early on I
> specified my function needed to only accept basic parameters ( no
> postional *args or *kwargs ) but now I am re-writing it and I want to
> accept these.  Is there anyway to determine what parameters are needed
> by a given function and format the arguments given appropriately.  My
> problem is that I feel my "Kludge"section is just that - a kludge.
> While it works for most cases it won't work for all (Try running this
> on function4 for example...).  I guess I have a problem with multiple
> if statements and I think it should just look to see what parameters
> are accepted and format them appropriately. Thoughts?
>
> If I am really screwing this up - please help me get back on the right
> track. I appreciate all of the help I get and it's great to learn from
> the experts.
>
> import random
> import threading
> import Queue
>
> class WorkerB(threading.Thread):
>
>     def __init__(self, *args, **kwargs):
>         self.id = kwargs.get('id', 0)
>         self.requestQ = kwargs.get('requestQ', None)
>         self.function = kwargs.get('function', None)
>         threading.Thread.__init__(self, name=self.__class__.__name__
> +"."+str(self.id))
>
>     def run(self):
>         while 1:
>             input = self.requestQ.get()
>             if input is None: break
>
>             # How do I look at the function and determine what it
> requires then apply that as an input?
>
>             # --------  Start Kludge ----------
>             tu=dic=False
>             if isinstance(input, tuple):
>                 try:
>                     if isinstance(input[0], tuple): tu = True
>                     elif isinstance(input[0], list): tu=True
>                 except: pass
>                 try:
>                     if isinstance(input[1], dict):dic = True
>                 except: pass
>                 if tu and dic:
>                     print "  -Tuple and list found"
>                     result = self.function(*input[0], **input[1])
>                 elif tu and not dic:
>                     print "  -Tuple found"
>                     result = self.function(*input[0])
>             elif isinstance(input, list):
>                 print "  -list only found"
>                 result = self.function(*input)
>             else:
>                 print "  -Unknown"
>                 result = self.function(input)
>
>             # --------  End Kludge ----------
>
> def function1(arg1):
>     print arg1
>
> def function2(*a ):
>     print "args", a
>
> def function3(*a, **kw):
>     print "args", a
>     print "kwargs", kw
>
> def function4(arg1, *a, **kw):
>     print arg1
>     print "args", a
>     print "kwargs", kw
>
> def main():
>
>
>     lod = 2
>     myQ=Queue.Queue()
>
>     # A basic example
>     print "\n== Example 1"
>     for x in range(lod):myQ.put( random.random() )
>     myQ.put(None)
>     a=WorkerB(requestQ=myQ, function=function1).start()
>
>     # Throw at is some args
>     print "\n== Example 2"
>     for x in range(lod):myQ.put(["a","b","c"])
>     myQ.put(None)
>     a=WorkerB(requestQ=myQ, function=function2).start()
>
>     # Throw at it both args and kwargs
>     print "\n== Example 3"
>     for x in range(lod):myQ.put(((1,2,3),
> {"input":random.random(),"loglevel":10}))
>     myQ.put(None)
>     a=WorkerB(requestQ=myQ, function=function3).start()
>
>     # Throw at it both args and kwargs
>     print "\n== Example 4 Does nothing!!"
>     for x in range(lod):myQ.put(("alpha",(1,2,3),
> {"input":random.random(),"loglevel":10}))
>     myQ.put(None)
>     a=WorkerB(requestQ=myQ, function=function4).start()
>
>
> if __name__ == '__main__':
>     main()
>


This is far more work than you need. Push an (args, kwargs) tuple into
your arguments queue and call self.function(*args, **kwargs).