51 lines
2.8 KiB
Markdown
51 lines
2.8 KiB
Markdown
 
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# pexpect — PyPI project page
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## Metadata
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| Field | Value |
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| Institute | Molodetz Institute — Research & Retrieval Division |
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| Subject | async-pty-process-testing |
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| Document type | Source Dossier |
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| Tier | 1 |
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| Source title | pexpect |
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| Source URL | https://pypi.org/project/pexpect |
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| Source publisher / author | pexpect maintainers (PyPI) |
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| Source type | repository |
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| Source date (published) | Unknown — not stated |
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| Date researched | 2026-10-09 |
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| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
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| Research method | web search synthesis |
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| Confidence | Medium |
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| Status | Active |
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## Summary
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pexpect is a well-established pure-Python library for spawning child applications, controlling them, and responding to expected patterns in their output. Its own documentation explicitly lists automated software testing as a use case. It is built on the stdlib `pty` module (Unix-only for its main features) and is a blocking/synchronous library.
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## Key findings
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- pexpect's documented purpose statement explicitly includes "automated software testing" alongside general automation.
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- Its core features require the stdlib `pty` module, which limits full functionality to Unix-like systems (some features — waiting for patterns from file descriptors or subprocesses — are also available on Windows, per the project's own docs).
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- It is blocking for async I/O (a third-party comparison table makes this claim, though the research flagged that table as coming from a competing library's vendor, i.e. a potentially biased source — still consistent with pexpect's own synchronous API design).
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## Pros / strengths
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- The most mature, widely-used library in this space, with a long track record specifically for testing interactive terminal programs.
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- `expect()`-style pattern matching against output is exactly the turn-boundary-detection problem `tai_test.py` needed to solve for REPL-mode testing.
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## Cons / limitations / caveats
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- Synchronous/blocking — adopting it inside `tai_test.py` would have meant either running it in a thread executor on every call or accepting that it blocks the event loop, neither of which fit an asyncio-native framework cleanly.
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- Not independently trialed in this research pass; findings are based on its documented feature list and use-case statement, not hands-on testing of its API against `tai.py`.
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## Relevance to tai
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Surveyed and explicitly not adopted. `tai_test.py`'s `ManagedProcess.wait_for_pattern()` is functionally pexpect's `expect()` reimplemented natively in asyncio (regex matching against an accumulating, ANSI-stripped buffer read from an `asyncio.StreamReader`), chosen specifically so the whole framework stays asyncio-native rather than mixing in a blocking dependency.
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## Changelog
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| Date | Change |
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| 2026-10-09 | Initial dossier created. |
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