Incomplete ordering¶
ID: py/incomplete-ordering
Kind: problem
Security severity:
Severity: warning
Precision: very-high
Tags:
- reliability
- correctness
Query suites:
- python-security-and-quality.qls
Click to see the query in the CodeQL repository
A class that implements an ordering operator (__lt__, __gt__, __le__ or __ge__) should implement all four in order that ordering between two objects is consistent and obeys the usual mathematical rules. If the ordering is inconsistent with default equality, then __eq__ and __ne__ should also be implemented.
Recommendation¶
Ensure that all four ordering comparisons are implemented as well as __eq__ and __ne__ if required.
It is not necessary to manually implement all four comparisons, the functools.total_ordering class decorator can be used.
Example¶
In this example only the __lt__ operator has been implemented which could lead to inconsistent behavior. __gt__, __le__, __ge__, and in this case, __eq__ and __ne__ should be implemented.
class IncompleteOrdering(object):
def __init__(self, i):
self.i = i
def __lt__(self, other):
return self.i < other.i
References¶
Python Language Reference: Rich comparisons in Python.