pampy

library0.3.0pypypi✓ verified 83d ago

Pampy is a library for pattern matching in Python, inspired by Haskell and OCaml. It provides concise syntax for matching patterns against data structures, including lists, dictionaries, and custom objects. The current stable version is 0.3.0, released in 2019. The library is in maintenance mode with low release cadence.

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pip install pampy

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INSTALL

IMPORT

SIG · PAMPY

pampy

devopspythonv0.3.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

match

✓ from pampy import match

Standard import for the main pattern matching function.

✓ from pampy import _

Wildcard pattern, similar to underscore in Haskell.

ANY

✓ from pampy import _

✗ from pampy import ANY

Pampy uses underscore for wildcard, not ANY.

Basic pattern matching with Pampy using match() function.

from pampy import match, _, REST result = match([1, 2, 3, 4], 1, "one", [1, _, 3, _], lambda a, b: f"1, {a}, 3, {b}", _, "default") print(result) # Output: 1, 2, 3, 4 # Note: Pattern matching is case-sensitive and order matters.

Debug

Known issues

gotchaUse underscore _ for wildcard, not ANY or other names.

fix

Import _ from pampy and use it as wildcard.

affects: all

gotchaPatterns in match are matched in order; the first matching branch is executed. Use default pattern (_) at the end.

fix

Always put the most specific patterns first and a catch-all _ last.

affects: all

gotchaPampy's match does not support Python's structural pattern matching syntax (PEP 634). Use its own DSL.

fix

Refer to Pampy's documentation for correct pattern syntax.

affects: all

deprecatedThe library has not been updated since 2019 and compatibility with newer Python versions may be limited.

fix

Consider using Python 3.10+ built-in match statement or alternative libraries.

affects: 0.3.0

Errors

Common errors & fixes

ImportError: cannot import name 'ANY' from 'pampy'

Attempting to import a non-existent name. The wildcard is '_' not 'ANY'.

fix

Use: from pampy import _

TypeError: match() takes 2 positional arguments but more were given

Incorrect call signature. match accepts (value, *patterns) where patterns are (pattern, result) pairs.

fix

Use: match(data, pattern1, result1, pattern2, result2, ...)

KeyError: '...' when matching dictionaries

Pattern matching with dictionary keys that do not exist in the matched dict.

fix

Ensure dictionary patterns have keys that exist. Use _ for optional keys with a default branch.

Upgrade

Version history

0.3.0latest on PyPI · released Nov 7, 2019

Audit

Dependencies

No dependency data recorded yet.

Agent activity

2 hits · last 30 days

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Resources

githubhttps://github.com/santinic/pampy ↗

homepagehttps://github.com/santinic/pampy ↗