pyformlang

library1.0.11pypypi✓ verified 86d ago

A Python framework for formal grammars, automata theory, and formal language processing. Current version is 1.0.11. Release cadence is irregular, primarily maintenance updates.

devops

pip install pyformlang

github ↗homepage ↗

INSTALL

IMPORT

SIG · PYFORMLANG

pyformlang

devopspythonv1.0.11

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.

cfg

✓ from pyformlang.cfg import CFG

✗ import cfg

CFG is inside pyformlang.cfg, not a top-level module.

rsa

✓ from pyformlang.rsa import RecursiveStateAutomaton

✗ from pyformlang import RecursiveStateAutomaton

RecursiveStateAutomaton lives in pyformlang.rsa.

regular_expression

✓ from pyformlang.regular_expression import Regex

✗ import regex

Not the standard 'regex' library; use pyformlang's Regex class.

Create a context-free grammar and check if a string is generated.

from pyformlang.cfg import CFG cfg = CFG.from_text(""" S -> A B A -> 'a' B -> 'b' """) print(cfg) print(cfg.contains("ab"))

Debug

Known issues

breakingIn version 1.0, the API was overhauled. Many classes (e.g., `FiniteAutomaton`, `CFG`) moved to submodules. Old code importing from `pyformlang.fa` or `pyformlang.cfg` directly may break.

fix

Update imports: `from pyformlang.finite_automaton import DeterministicFiniteAutomaton`.

affects: >=0.5, <1.0

deprecatedThe `pyformlang.regular_expression` module's `Regex` constructor no longer accepts a string with implicit concatenation; use explicit operators.

fix

Use `Regex('a b')` with spaces or explicit '.' for concatenation.

affects: >=1.0.0

gotchaCFG emptiness check (`cfg.is_empty()`) may return `True` for grammars that generate the empty language even if they look non-empty due to cycles. Always check reachable and productive symbols first.

fix

Use `cfg.get_reachable_symbols()` and `cfg.get_productive_symbols()` before calling `is_empty()`.

affects: all

Errors

Common errors & fixes

AttributeError: module 'pyformlang' has no attribute 'cfg'

Importing `pyformlang.cfg` directly without the submodule import.

fix

Use `from pyformlang.cfg import CFG` instead of `import pyformlang.cfg`.

OSError: [WinError 126] The specified module could not be found

Missing C++ runtime on Windows due to compiled extensions.

fix

Install Microsoft Visual C++ Redistributable for Visual Studio 2015-2022.

Upgrade

Version history

1.0.11latest on PyPI · released Mar 18, 2025

Audit

Dependencies

No dependency data recorded yet.

Agent activity

4 hits · last 30 days

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Resources

githubhttps://github.com/Aunsiels/pyformlang ↗

homepagehttps://github.com/Aunsiels/pyformlang ↗