Question

bit of an issue with a function I’m writing for adding and subtracting a value located within a class.

I’m trying to pass a value that I’ve read in from a csv to my add function. This value is a decimal value (e.g. 500.00) I’ve tried eliminating the trailing 0’s to make it just 500, this didn’t work either. I keep getting:

TypeError: add() takes exactly one argument (two given).

Even though I have a print statement confirming its only trying to pass in the 500.

Here’s my function:

def add(amount):
    self.total = self.total + amount

It’s being called by v.add(i) Even if I set i to an arbitray integer value it still results in the same error. I am relatively inexperience with python, so perhaps there is something simple I’m missing here. Thanks.

Answer 1

class Myclass(object):
    def __init__(self, total=0.):
        self.total = total

    def add(self, amount):     # <= needs `self` parameter
        self.total += amount

v = Myclass()
v.add(2.)

When you call an object method, it implicitly passes a reference to the object – so calling v.add(something) actually calls Myclass.add(v, something).

Voila – two parameters, when you told it to only expect one…