Subclass init Calls Parent

ID

python.init_call_parent

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Python

Tags

reliability, suspicious-construct

Description

Reports init methods inside a subclass that do not invoke the parent’s constructor. Without super().init(…​), any state the parent class needs to initialise on the instance never runs, and the resulting object is partially constructed in ways the parent’s other methods rely on.

class Bad(Parent):
    def __init__(self):              # FLAW — Parent.__init__ never runs
        self.x = 1

class Good(Parent):
    def __init__(self):
        super().__init__()
        self.x = 1

Rationale

Skipping the parent constructor is sometimes intentional (the parent does heavy work the subclass does not need), but the silent failures it introduces — methods of the parent that rely on attributes set in init raising AttributeError later — are usually worse than the few microseconds saved.

The rule fires only when the class extends from at least one named super-type other than object; classes with no explicit base are out of scope.

Remediation

Add the super().init(…​) call at the start of the subclass init. Forward whatever arguments the parent expects:

class Good(Parent):
    def __init__(self, x):
        super().__init__(x)
        self.cache = {}

If the parent constructor really must be skipped, document the reason in a comment so future readers do not "fix" it back.

References