Function Defaults - avoiding unneccerary combinations of arguments at input

[Rob Gaddi]

On Wed, 25 Mar 2015 21:50:40 +0200, Ivan Evstegneev wrote:

> Hello again ^_^,
> 
> Googled a bit, and found only one, a "ValueError" exception, but still
> don't understand how it should be implemented in my case.
> 
> Should my code look like this one:
> 
> def  my_fun(history=False, built=False, current=False, topo=None,
> full=False, file=None):
> 	try:
> 		if currnet and full:
> 			do something_1
> 		elif current and file:
> 			do something_2
> 		elif history and full and file:
> 			do something_3
> 	
> 	except ValueError:
> 		print("No valid input! Please try again ...")
> 
> 
> 	...... some code here..............
> 
> 
> Or I'm just too optimistic ^_^?
> 
> Thanks in advance,
> 
> Ivan.
> 

A) Please don't top-post.  Put your new stuff below previous context, so 
it flows in readable order.

B) You've got the concept backwards.  You're not trying to catch a 
ValueError because one came up below your function.  Your function was 
called incorrectly, and you're kicking the responsibility for dealing 
with it back to the guy who got it wrong.

def my_fun(....):
    if invalid_argument_combination:
       raise ValueError('Hey jerk, read the documentation.')

    # otherwise you do your thing in here.


-- 
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order.  See above to fix.