about things
trim patterns.md - remove duplication
- remove filterable decorator (covered in mcp.md)
- remove lowercase aesthetic (implicit in notes style)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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languages/python/language/patterns.md
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languages/python/language/patterns.md
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# callers can catch AppError for all, or specific types
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```
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## decorators that modify signatures
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add parameters dynamically:
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```python
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import inspect
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from functools import wraps
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def filterable(fn):
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"""add _filter parameter for jmespath filtering."""
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@wraps(fn)
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async def wrapper(*args, _filter: str | None = None, **kwargs):
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result = await fn(*args, **kwargs)
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if _filter:
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import jmespath
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return jmespath.search(_filter, result)
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return result
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# modify signature to include new param
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sig = inspect.signature(fn)
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params = list(sig.parameters.values())
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params.append(inspect.Parameter(
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"_filter",
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inspect.Parameter.KEYWORD_ONLY,
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default=None,
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))
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wrapper.__signature__ = sig.replace(parameters=params)
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return wrapper
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```
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the wrapper's signature now includes `_filter`. IDEs and schema generators see it.
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from [pdsx/mcp/filterable.py](https://github.com/zzstoatzz/pdsx/blob/main/src/pdsx/mcp/filterable.py)
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## argparse for CLIs
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argparse is stdlib. subparsers with aliases give you unix-style commands:
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console = Console()
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```
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## lowercase aesthetic
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docstrings, comments, and output in lowercase:
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```python
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"""list records in a collection."""
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def list_records(collection: str) -> list[dict]:
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"""list records from the specified collection.
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args:
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collection: the collection to list from
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returns:
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list of record dictionaries
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"""
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```
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consistent voice throughout.
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sources:
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- [pdsx](https://github.com/zzstoatzz/pdsx)