python runtime_error ai_generated true

AssertionError

ID: python/assertionerror

Also available as: JSON · Markdown
90%Fix Rate
90%Confidence
50Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
311 active — — —

Root Cause

Assert statement failed. Never use assert for data validation — it's stripped with python -O.

generic

Workarounds

  1. 95% success Read the assert message to understand what condition failed, then fix the data/logic 
    # The assert message tells you what failed:
assert len(items) > 0, f'Expected non-empty list, got {items}'
# Read the message, trace back to where items is populated

    Sources: https://docs.python.org/3/reference/simple_stmts.html#the-assert-statement

  2. 88% success Replace assert with proper if/raise ValueError for production validation 
    # Before (stripped by python -O):
assert age >= 0
# After (always runs):
if age < 0:
    raise ValueError(f'Age must be non-negative, got {age}')

    Sources: https://docs.python.org/3/reference/simple_stmts.html#the-assert-statement

Dead Ends

Common approaches that don't work:

  1. Remove the assert statement 80% fail

    Hides the bug — the assertion caught a real problem

  2. Wrap in try/except AssertionError 75% fail

    Silences the error but doesn't fix the cause

Error Chain

Frequently confused with: