prune-source

prune-source is a small Rust/Ruff accelerator for static API analysis. It lexes Python source and removes function implementation suites that an API visitor does not need, allowing CPython to construct and walk a much smaller abstract syntax tree. It does not build an intermediate Ruff AST.

pip install prune-source

import ast

from prune_source import prune_source

source = "def answer() -> int:\n    return 42\n"
pruned = prune_source(source)
tree = compile(
    source if pruned is None else pruned,
    "example.py",
    "exec",
    ast.PyCF_ONLY_AST,
    optimize=1,
)

The pruner preserves function signatures, decorators, docstrings, class bodies, and class __init__ implementations. Other function suites are replaced by pass while physical line layout is retained. Removed multiline content is collapsed to empty lines rather than padded with spaces; for indented suites, the pass remains on the original final implementation line so definition end-line metadata stays stable. Nested function suites inside __init__ are pruned as well.

The input is expected to be valid for the Python interpreter that will compile it. The lexer does not perform grammar or version validation. prune_source returns None when there is nothing to prune; callers should compile their original source in that case.

Ruff's internal parser crate is vendored because its public lexer API does not expose token ranges. The vendored copy has exactly two source changes, making the range and flag accessors public; see vendor/ruff_python_parser/UPSTREAM.md.

Building from source requires Rust 1.96 or newer.