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.

The pruner uses Ruff's published parser crate to read token ranges and flags without constructing a syntax tree. Ruff's Rust API is unstable, so its component crates are pinned to the same version.

Building from source requires Rust 1.96 or newer.