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Maybe missing ‘self’ in comparison

ID: py/comparison-missing-self Kind: problem Security severity: Severity: warning Precision: very-high Tags: - quality - reliability - correctness - external/cwe/cwe-570 - external/cwe/cwe-571 Query suites: - python-code-quality.qls - python-security-and-quality.qls

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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