Missing call to
__init__ during object initialization¶
ID: py/missing-call-to-init Kind: problem Severity: error Precision: high Tags: - reliability - correctness Query suites: - python-security-and-quality.qls
Python, unlike statically typed languages such as Java, allows complete freedom when calling methods during object initialization. However, standard object-oriented principles apply to Python classes using deep inheritance hierarchies. Therefore the developer has responsibility for ensuring that objects are properly initialized when there are multiple
__init__ methods that need to be called.
__init__ method of a superclass is not called during object initialization it is likely that that object will end up in an incorrect state.
A call to the
__init__ method of a superclass during object initialization may be omitted:
When a subclass calls the
__init__method of the wrong class.
When a call to the
__init__method of one its base classes is omitted.
When multiple inheritance is used and a class inherits from several base classes, and at least one of those does not use
super()in its own
Either be careful to explicitly call the
__init__ of the correct base class, or use
super() throughout the inheritance hierarchy.
Alternatively refactor one or more of the classes to use composition rather than inheritance.
In this example, explicit calls to
__init__ are used, but
SportsCar erroneously calls
Vehicle.__init__. This is fixed in
FixedSportsCar by calling
class Vehicle(object): def __init__(self): self.mobile = True class Car(Vehicle): def __init__(self): Vehicle.__init__(self) self.car_init() #Car.__init__ is missed out. class SportsCar(Car, Vehicle): def __init__(self): Vehicle.__init__(self) self.sports_car_init() #Fix SportsCar by calling Car.__init__ class FixedSportsCar(Car, Vehicle): def __init__(self): Car.__init__(self) self.sports_car_init()