Using instance variable in Python class function definition

Question

How can I set the default value in the class definition to one of the class' instance variable?

class SomeClass:
    def __init__(self, data):
        self.data = data

    def do_something(self, data_file=self.data):  # Here

        # modify the data and return to itself using recursion.
        if something:
            return self.do_something(data_file)
        else:
            return data_file

Function defaults are determined *once*, when the function is created. They are not created each time the method is called. — Martijn Pieters, Jul 08 '16 at 10:15
*"I want to use recursion so I can't access the value inside the function"* - it's not clear why you think those two things go together. — jonrsharpe, Jul 08 '16 at 10:15
Another duplicate: [How to change default of function parameter for an instance of an object?](https://stackoverflow.com/q/32013733) — Martijn Pieters, Jul 08 '16 at 10:16
Jonrsharpe link me to a question that is also marked as duplicate. — tommyip, Jul 08 '16 at 10:17
@Red2awn: yes, and so did I. There is a canonical there but both jon and I provided more context. — Martijn Pieters, Jul 08 '16 at 10:18
@Red2awn also the fact that we could do so suggests you hadn't done much looking yourself... — jonrsharpe, Jul 08 '16 at 10:19

score 1 · Answer 1 · answered Jul 08 '16 at 10:15

1

Use another value, and check for it:

def do_something(self, data_file=None):
    if data_file is None:
        data_file = self.data

    ...etc...

answered Jul 08 '16 at 10:15

RemcoGerlich

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Using instance variable in Python class function definition

1 Answers1