Four or more `if`/`elif isinstance(x, ...)` branches testing the same variable. Type dispatch written out by hand, one branch per type.
Each example shows the exact code shape the rule is looking for, then the smallest version that keeps the intent without hiding risk or adding noise.
def to_json(value):
if isinstance(value, datetime):
return value.isoformat()
elif isinstance(value, Decimal):
return str(value)
elif isinstance(value, UUID):
return str(value)
elif isinstance(value, Enum):
return value.value
return valueDeterministic line match: counts `if`/`elif isinstance(name, ...)` branches on the same variable at the same indentation and flags the ladder at four or more.
@singledispatch
def to_json(value):
return value
to_json.register(datetime, lambda value: value.isoformat())
to_json.register(Decimal, str)
to_json.register(UUID, str)
to_json.register(Enum, lambda value: value.value)Use a handler map keyed by type, `functools.singledispatch`, or a protocol, or normalize inputs into one representation before the logic runs.
Asked to support one more input type, agents add one more `elif isinstance` branch. Across iterations the ladder grows instead of the design absorbing new cases.
ai-slop/python-isinstance-ladder
ai-slop
Deterministic line match: counts `if`/`elif isinstance(name, ...)` branches on the same variable at the same indentation and flags the ladder at four or more.
Ladders of three or fewer branches, and branches that test different variables, are not flagged.
Shipped in aislop v0.9.4 as one of four Python verbosity rules drawn from SlopCodeBench (arXiv 2603.24755).