Parse Python Traceback Stack Trace

Understanding Python Tracebacks

Python uses the term "traceback" for its stack traces. A traceback shows the sequence of function calls that led to an exception, displayed in most-recent-call-last order --- the opposite of JavaScript and Java conventions.

Standard Traceback Format

Traceback (most recent call last):
  File "/app/main.py", line 45, in handle_request
    result = process_data(payload)
  File "/app/services/processor.py", line 128, in process_data
    validated = schema.validate(data)
  File "/app/lib/validator.py", line 67, in validate
    raise ValidationError(f"Invalid field: {field}")
ValidationError: Invalid field: email

Traceback Components

Each frame in a Python traceback contains:

• File --- the absolute or relative path to the Python file
• line --- the line number in the file
• in --- the function or method name (<module> for top-level code)
• Code snippet --- the actual line of code (displayed on the next line, indented)

Reading Order

The first frame (top) is the outermost call, and the last frame (bottom) is where the exception was raised. The error type and message appear on the very last line. This is the reverse of JavaScript traces.

Exception Chaining

Python 3 supports exception chaining with raise X from Y and implicit chaining (when an exception occurs while handling another). Chained tracebacks show multiple Traceback blocks connected by During handling of the above exception, another exception occurred: or The above exception was the direct cause of the following exception:.

Common Python Exception Types

• TypeError --- wrong type passed to a function
• ValueError --- correct type but invalid value
• KeyError --- dictionary key not found
• AttributeError --- attribute does not exist on an object
• ImportError/ModuleNotFoundError --- module cannot be imported