Explicit return in __init__¶
__init__ is a special Python method that is automatically called when memory is allocated for a new object. The sole purpose of
__init__ is to initialize the values of instance members for the new object. Using
__init__ to return a value implies that a program is using
__init__ to do something other than initialize the object. This logic should be moved to another instance method and called by the program later, after initialization.
__init__ method of the
Rectangle class below attempts to return the area of the rectangle within the
__init__ method. This violates the rule of only using
__init__ to initialize instance members.
class Rectangle: def __init__(self, width, height): self.width = width self.height = height self.area = width * height # causes "Explicit return in __init__" error return self.area
Remove the return statement from the
return statement in the
__init__ method that is returning a value.
class Rectangle: def __init__(self, width, height): self.width = width self.height = height self.area = width * height # return statement removed from here
Move the program logic to another instance method¶
There is no reason why the
Rectangle class MUST return the area immediately upon initialization. This program logic should be moved to a separate method of the
Rectangle class. The program can call the method later, after the object has successfully initialized.
class Rectangle(object): def __init__(self, width, height): self.width = width self.height = height self._area = width * height @property # moved the logic for returning area to a separate method def area(self): return self._area
Note that the class must inherit from
object now, since the
property decorator only works for new style classes.
- PyLint - E0101, return-in-init
- Python Language Reference - object.__init__(self[, …])