Getting a RecursionError in a python class

Question

I have a Product class defined in Python as below:

class Product:
    @property
    def price(self):
        return self.price

    @price.setter
    def price(self, value):
        if value < 10:
            raise ValueError("price can't be negative")
        self.price = value

When I try to set the price attribute of a new instance of Product (prod):

prod = Product()
prod.price = 25
print(prod.price)

I get an error saying:

RecursionError: maximum recursion depth exceeded

Can someone please explain what I'm doing wrong here...

You are trying to get/set a property value by getting/setting the property which in turn tries to get/set the property value by getting/setting the property which in turn... — Michael Butscher
– Michael Butscher, Commented May 15, 2019 at 19:05
Your getter and setter calls themselves recursively: return self.price self.price = value — juanpa.arrivillaga
– juanpa.arrivillaga, Commented May 15, 2019 at 19:05

adrtam · Accepted Answer · 2019-05-15 19:06:43Z

5

Recursion occurs here:

@price.setter
def price(self, value):
    self.price = value

which self.price = will trigger the same price() function as you make it a setter. The better (i.e., more conventional) way is to use self._price to hold your value.

answered May 15, 2019 at 19:06

adrtam

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1 Comment

psj01 Over a year ago

Thanks. I understand the problem now.

Prune · Accepted Answer · 2019-05-15 19:09:27Z

1

    self.price = value

This is a recursive reference to the setter itself. Look up how to write a setter; you'll see the problem. You need to refer to the pseudo-private variable:

    self._price = value

answered May 15, 2019 at 19:09

Prune

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1 Comment

psj01 Over a year ago

Thanks. make sense to me now.

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