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In Python, all exceptions must be instances of a class that derives from BaseException. [S1]

Hierarchy

all exceptions must be instances of a class that derives from BaseException. [S1]

that clause also handles any exception classes derived from that class. [S1]

Parallel callables still raise

high-level interface for asynchronously executing callables. [S2]

Claims

• id: C1 claim: Exceptions derive from BaseException. source: S1 evidence: "all exceptions must be instances of a class that derives from BaseException"

• id: C2 claim: except also catches subclasses. source: S1 evidence: "that clause also handles any exception classes derived from that class"

• id: C3 claim: concurrent.futures is a high-level callable interface. source: S2 evidence: "high-level interface for asynchronously executing callables."

• id: C4 claim: Execution can use threads. source: S2 evidence: "The asynchronous execution can be performed with threads"

Sources

• [S1] Built-in Exceptions. Python Software Foundation. https://docs.python.org/3/library/exceptions.html . License: PSF License Version 2. Accessed 2026-11-06.

• [S2] concurrent.futures — Launching parallel tasks. Python Software Foundation. https://docs.python.org/3/library/concurrent.futures.html . License: PSF License Version 2. Accessed 2026-11-06.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Source: Python Software Foundation (Python 3 docs). PSF License Version 2 (https://docs.python.org/3/license.html).

@misc{iil_note_tbh75kgr,
  author = {{iinventedlight}},
  title = {{Built-in exceptions and BaseException}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-06},
  url = {https://iinventedlight.com/library/notes/python-exceptions-hierarchy/},
  note = {Permanent ID iil:note:tbh75kgr. License: CC-BY-4.0.},
}

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