Error Message and Traceback

An error message describes a failure. In Python, an exception interrupts the current operation unless it is handled; the report names its type and usually describes what failed. A traceback shows the active chain of calls, printed outermost first, followed by the exception type and message. Handling an exception can let the program continue.

Read the last line first to identify the exception type and the operation or value involved. Then inspect the innermost relevant frame and work outward through its callers to trace how that value arrived. The line that raised the exception is evidence of where it surfaced; neither the innermost nor the outermost frame automatically identifies the root cause.

Separate reusable wording from task-specific details when searching. Remove private paths or identifiers, but keep diagnostic information such as type names, function names, and format directives, even when they are quoted. Inspect the original message locally to locate the affected input. Wording can change between versions, so include the version or generalize the query when needed.

An exception and a silent wrong answer need different checks. Exceptions provide diagnostic evidence; incorrect results may require an explicit comparison with an expected value to become visible. Catch exceptions where recovery is defined, and preserve enough context to diagnose failures. A broad handler that discards the exception and its traceback can hide the evidence.

References: Python errors and exceptions, Python traceback module. See it in use in Researching Errors and Organizing Analytical Work.