Optional Argument for Function in Python

Question

If i try to give a function an optional argument, this way it won't work:

def speed(self, max, now):
    self.min = 0
    self.max = max
    if now != None:
        self.now = now
    else:
        self.now = 0
    return self.max, self.now

Can someone help me to understand this and how to do it better? Do i really need the if statement? Maybe there is an easier and faster way with some kind of special argument?

It's in a very early step of the official tutorial: [Default Argument Values](https://docs.python.org/3/tutorial/controlflow.html#default-argument-values). — Matthias, Apr 03 '16 at 08:38

score 2 · Accepted Answer · answered Apr 03 '16 at 08:31

Use a default argument value to set now to 0 when omitted:

def speed(self, max, now=0):
    self.min = 0
    self.max = max
    self.now = now
    return self.max, self.now

Now the caller can simply omit specifying a value for the now argument:

some_instance.speed(42)

would leave now set to 0.

Optional Argument for Function in Python

1 Answers1