Maybe missing ‘self’ in comparison¶
ID: py/comparison-missing-self
Kind: problem
Security severity:
Severity: warning
Precision: very-high
Tags:
- reliability
- maintainability
- external/cwe/cwe-570
- external/cwe/cwe-571
Query suites:
- python-security-and-quality.qls
Click to see the query in the CodeQL repository
When two identical expressions are compared it is typically an indication of a mistake, since the Boolean value of the comparison will always be the same. Often, it can indicate that self has been omitted.
Recommendation¶
It is never good practice to compare a value with itself. If self has been omitted, then insert it. If the constant behavior is indeed required, use the Boolean literals True or False, rather than encoding them obscurely as x == x or similar.
Example¶
class Customer:
def __init__(self, data):
self.data = data
def check_data(self, data):
if data != data: # Forgotten 'self'
raise Exception("Invalid data!")
#Fixed version
class Customer:
def __init__(self, data):
self.data = data
def check_data(self, data):
if self.data != data:
raise Exception("Invalid data!")
References¶
Python Language Reference: Comparisons.
Common Weakness Enumeration: CWE-570.
Common Weakness Enumeration: CWE-571.