*args question
Tim Chase
python.list at tim.thechases.com
Wed Mar 25 11:28:27 EDT 2009
grocery_stocker wrote:
> On Mar 25, 7:05 am, grocery_stocker <cdal... at gmail.com> wrote:
>> Given the following code...
>>
>> #!/usr/bin/env python
>>
>> import time
>> import thread
>>
>> def myfunction(string,sleeptime,*args):
>> while 1:
>>
>> print string
>> time.sleep(sleeptime) #sleep for a specified amount of time.
>>
>> if __name__=="__main__":
>>
>> thread.start_new_thread(myfunction,("Thread No:1",2))
>>
>> while 1:pass
>>
>> Taken from following URL....http://linuxgazette.net/107/pai.html
>>
>> How can myfunction() extract the tuple ("Thread No:1",2) from
>> start_new_thread() if myfunction is only being passed the single arg
>> ("Thread No:1",2)
>
>
> The only thing that I think of is that the tuple ("Thread No:1",2) is
> somehow being extract before it gets passed to myfunction(). Ie,
> something like the following...
>
> [cdalten at localhost ~]$ python
> Python 2.4.3 (#1, Oct 1 2006, 18:00:19)
> [GCC 4.1.1 20060928 (Red Hat 4.1.1-28)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>>>> def myfunction(first, second, *args):
> ... print "The formal args are: ", args
> ... print "the first value is:", first
> ... print "the second value is:", second
> ...
>>>> a, b = (1,2)
>>>> myfunction(a,b)
> The formal args are: ()
> the first value is: 1
> the second value is: 2
and if you call "myfunction(1,2,("Thread No:1",2))", you should
get something like
The formal args are: (('Thread No:1', 2),)
the first value is: 1
the second value is: 2
It's a list of the various items you put in:
def show_args(first, second, *args):
print "first", first
print "second", second
for i, arg in enumerate(args):
print "#%i %s" % (i, arg)
So you can either access "args[0]" (which is a bit dangerous, as
you assume there may be a value when there's not), or you can do
the more traditional thing of just treating it like a list as
above (e.g. iterating over it or using it in a list-comprehension).
-tkc
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