LowFile-scopePython Plug & play

Avoid modifying input parameters

Treat function inputs as immutable; copy before mutation (e.g., dict.copy(), list(x)).

Why this matters

Prevents surprising side effects and makes functions safer to reuse.

Side-by-side examples engineers can pattern-match during review.

Avoid

def normalize(d: dict) -> dict:
    d['status'] = d['status'].lower()
    return d

Prefer

def normalize(d: dict) -> dict:
    out = {**d}
    out['status'] = out.get('status', '').lower()
    return out

Bad

def f(x): x.append(1); return x

Good

def f(xs): ys = list(xs); ys.append(1); return ys

From the same buckets as this rule.

Critical
Avoid Duplicating String Literals
Store repeated string literals in constants or variables to improve maintainability and reduce redundancy.
duplication-complexitymaintainability
Critical
Avoid Empty Methods
Detect methods that have an empty body. If a method is empty, ensure that a comment is present explaining why it remains unimplemented.
maintainabilityreadability-refactor
Critical
Avoid modifying built-in prototypes
Detect modifications to built-in prototypes. Modifying built-in objects can lead to compatibility issues and unexpected behavior. Recommend creating helper functions instead.
maintainabilitysecurity-hardening