[Tutor] Why include "*args" in a function's parameter list when no args are ever passed in?

[boB Stepp]

On Thu, Sep 03, 2020 at 10:13:13AM +0200, Peter Otten wrote:
>boB Stepp wrote:
>
>> # Called when the selection in the listbox changes; figure out
>> # which country is currently selected, and then lookup its country
>> # code, and from that, its population.  Update the status message
>> # with the new population.  As well, clear the message about the
>> # gift being sent, so it doesn't stick around after we start doing
>> # other things.
>> def showPopulation(*args):
>       print(args)
>>      idxs = lbox.curselection()
>>      if len(idxs)==1:
>>          idx = int(idxs[0])
>>          code = countrycodes[idx]
>>          name = countrynames[idx]
>>          popn = populations[code]
>>          statusmsg.set("The population of %s (%s) is %d" % (name, code,
>>          popn))
>>      sentmsg.set('')
>>
>> I don't understand why he just doesn't leave the parameters area in the
>> function definition blank instead of inserting "*args" which never gets
>> used.  Why would one do this?
>
>Add the print statement and you'll see that while the initial explicit call
>is without arguments subsequent calls triggered by changing the listbox
>selection pass an Event object.

Ah!  I forgot about this.

>Personally I would still prefer the signature
>
>def showPopulation(_event=None):
>    ...

If I had seen "_event=None" instead of "*args" I would have immediately
recalled what I had otherwise forgotten and never have asked my question!

Thanks, Peter!

-- 
Wishing you only the best,

boB Stepp