Optional Argument for Function in Python [duplicate]

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. — Matthias
– Matthias, Commented Apr 3, 2016 at 8:38

Martijn Pieters · Accepted Answer · 2016-04-03 08:31:32Z

2

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.

answered Apr 3, 2016 at 8:31

Martijn Pieters

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