在__init__中使用属性设置器

Question

How do I use a Property setter in __init__ without pylint complaining that the attribute has been defined outside __init__ ?

For example, the following code only produces one exception which is caught in the try clause at the bottom.

class CircleNotUsingSetterInInit(object):

    def __init__(self, radius):
        # Notice underscore in 'self.radius
        self._radius = radius

    @property
    def radius(self):
        return self._radius

    @radius.setter
    def radius(self, radius):
        if radius < 0:
            raise ValueError("Radius must be non-negative")
        self._radius = radius


class CircleUsingSetterInInit(object):

    def __init__(self, radius):
        # Notice lack of underscore in 'self.radius'
        self.radius = radius

    @property
    def radius(self):
        return self._radius

    @radius.setter
    def radius(self, radius):
        if radius < 0:
            raise ValueError("Radius must be non-negative")
        # From pylint:
        # Attribute '_radius' defined outside __init__ (attribute-defined-outside-init)
        self._radius = radius


CircleNotUsingSetterInInit(5)
CircleNotUsingSetterInInit(-1)
CircleUsingSetterInInit(5)
try:
    CircleUsingSetterInInit(-1)
except ValueError:
    print("caught exception")

I'm using Python 2.7.10.

Answer 1

The warning is completely safe to ignore in this case. Pylint just doesn't "see" that, it's rather complex to notice without doing syntax parsing.

You can add a comment for pylint to disable this warning locally like this:

class CircleUsingSetterInInit(object):

    # ....

    @radius.setter
    def radius(self, radius):
        if radius < 0:
            raise ValueError("Radius must be non-negative")
        # pylint: disable=W0201
        self._radius = radius

---

W0201 is the code for attribute-defined-outside-init , which is the warning you receive according to the docs . You should always add such disable comments as close to the source as possible, so that pylint works normally for the rest of the file.