How to convert an custom class object to a tuple in Python? [closed]

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If we define __str__ method in a class:

    class Point():
        def __init__(self, x, y):
            self.x = x
            self.y = y


        def __str__(self, key):
            return '{}, {}'.format(self.x, self.y)

We will be able to define how to convert the object to the str class (into a string):

    a = Point(1, 1)
    b = str(a)
    print(b)

I know that we can define the string representation of a custom-defined object, but how do we define the list —more precisely, tuple— representation of an object?

Give us some example code of something you would like to convert to a tuple so we can help. Also check this: stackoverflow.com/questions/12836128/… -> It is specific to lists but it might help you. — Angelos Chalaris
– Angelos Chalaris, Commented Jun 5, 2016 at 7:11

holdenweb · Accepted Answer · 2019-02-07 14:13:42Z

46

The tuple "function" (it's really a type, but that means you can call it like a function) will take any iterable, including an iterator, as its argument. So if you want to convert your object to a tuple, just make sure it's iterable. This means implementing an __iter__ method, which should be a generator function (one whose body contains one or more yield expressions). e.g.

>>> class SquaresTo:
...     def __init__(self, n):
...         self.n = n
...     def __iter__(self):
...         for i in range(self.n):
...             yield i * i
...
>>> s = SquaresTo(5)
>>> tuple(s)
(0, 1, 4, 9, 16)
>>> list(s)
[0, 1, 4, 9, 16]
>>> sum(s)
30

You can see from the example that several Python functions/types will take an iterable as their argument and use the sequence of values that it generates in producing a result.

edited Feb 7, 2019 at 14:13

answered Jun 5, 2016 at 7:44

holdenweb

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2 Comments

acgtyrant Over a year ago

I find we can define __getitem__ method to make the class iterable too.

holdenweb Over a year ago

I explained the iteration protocols in a talk to PyData London earlier this year. It might help - there is also a video of the session.

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