[Tutor] question about *args and functions

[Kent Johnson]

shawn bright wrote:
> lo there all,
> 
> if i have a function that sometimes needs a value passed to it and 
> sometimes not, is this where i use *args ?

No, use an optional argument.

> 
> like this
> 
> def some_function(req_var, req_var2, un_req_var):
>     do some stuff
>     return value
> 
> how would i use this if sometimes i need to process un_req_var and 
> sometimes not ?

def some_function(req_var, req_var2, un_req_var=None):
     do some stuff
     return value

Now the caller can write some_function(1, 2) or some_function(1, 2, 3). 
You can distinguish the two by checking for 'un_req_var is None'.

If None is a legitimate value for un_req_var then you need to pick some 
other sentinal value. If there is no built-in value that works, create 
your own:

missing = object()
def some_function(req_var, req_var2, un_req_var=missing):

Kent