I'm writing a program (see below) where the user can set parameters x[0] and x[1]. Sometimes the user is not setting x[1] as it's not always needed (tested with #x[1]=2). If x[1] is not set, I want the function to use the default b=5 as value. When testing, as expected, when function1 is called, it gives me an error saying x[1] is missing. I tried a lot playing aroung with "=None" etc, but can't get it to recognize x[1] is non-existing and using b=5 as default.
Anyone knows a elegant pythonian way to implement this? (I guess there's a simple way that slipped my tired mind or I, as beginner, simply don'T know up to now :)
Thx, Toby
def function1(a, b=5):
print(a)
print(b)
x={}
x[0]=1
#x[1]=2
function1(x[0],x[1])
Your function definition can stay the same:
def function1(a, b=5):
print(a)
print(b)
Your way of calling the function needs to change.
For positional arguments don't use a dict {}, use a list []:
x = [1, 2]
function1(*x) # prints 1 & 2
x = [1]
function1(*x) # prints 1 & 5
For named arguments use a dict (but then you have to call the values a and b, like the function does):
x = {"a": 1, "b": 2}
function1(**x) # prints 1 & 2
x = {"a": 1}
function1(**x) # prints 1 & 5
When used in a function call, the * operator unpacks lists, and the ** operators unpacks dicts into the function's arguments.