CodeQL documentation
CodeQL resources

__eq__ not overridden when adding attributes

ID: py/missing-equals Kind: problem Security severity: Severity: warning Precision: high Tags: - quality - reliability - correctness Query suites: - python-code-quality.qls - python-security-and-quality.qls

Click to see the query in the CodeQL repository

A class that defines attributes that are not present in its superclasses may need to override the __eq__() method (__ne__() should also be defined).

Adding additional attributes without overriding __eq__() means that the additional attributes will not be accounted for in equality tests.

Recommendation

Override the __eq__ method.

Example

In the following example the ColorPoint class subclasses the Point class and adds a new attribute, but does not override the __eq__ method.

class Point(object): def __init__(self, x, y): self._x = x self._y = y def __repr__(self): return 'Point(%r, %r)' % (self._x, self._y) def __eq__(self, other): if not isinstance(other, Point): return False return self._x == other._x and self._y == other._y class ColorPoint(Point): def __init__(self, x, y, color): Point.__init__(self, x, y) self._color = color def __repr__(self): return 'ColorPoint(%r, %r)' % (self._x, self._y, self._color) #ColorPoint(0, 0, Red) == ColorPoint(0, 0, Green) should be False, but is True. #Fixed version class ColorPoint(Point): def __init__(self, x, y, color): Point.__init__(self, x, y) self._color = color def __repr__(self): return 'ColorPoint(%r, %r)' % (self._x, self._y, self._color) def __eq__(self, other): if not isinstance(other, ColorPoint): return False return Point.__eq__(self, other) and self._color = other._color

References