Redact Secret for Python

Deterministic secret detection and redaction for CPython, over the same Rust core that backs the JavaScript, Rust, and CLI surfaces of Redact Secret. Every built-in detector runs in Rust; there is no pure-Python fallback implementation to drift from it.

The distribution is redact-secret and the import name is redact_secret. The product name is Redact Secret everywhere; per PEP 503, redact-secret and redact_secret normalize to the same PyPI project identity, so no registry fallback name is needed — see docs/rust-workspace.md.

The version in the development manifests is not a published release. See release status for installable versions.

This directory is the canonical Python binding decision-release-bindings-in-lockstep requires before the separately created secret-scan-python GitHub repository (empty today) is archived with a redirect to here; that prepared redirect text lives in docs/python-repository-redirect.md.

Install

pip install redact-secret

Wheels are CPython 3.10+ abi3: one wheel per platform serves every supported interpreter, and installing one needs no Rust toolchain and no compiler. See Supported wheels. Where no wheel applies, pip falls back to the source distribution, which does need Rust — see Building from source.

Use

import redact_secret

findings = redact_secret.scan(text)
redacted = redact_secret.redact(text, findings)

# or, to guarantee the findings and the redacted text agree:
result = redact_secret.scan_and_redact(text)
result.text, result.findings

Ranges on every DetectedFinding and Finding are Unicode code point offsets (redact_secret.RANGE_UNIT == "unicode-code-points"), so they index a str the way Python itself does.

scan, redact, and scan_and_redact default to a 64 MiB input bound and a 50,000 finding-count bound, raising InputLimitExceededError/ FindingLimitExceededError rather than returning a truncated result. Pass limits=redact_secret.WholeInputLimits(max_input_bytes=..., max_findings=...) to raise or lower them.

For input that arrives in pieces, IncrementalSanitizer sanitizes a bounded session chunk by chunk. Independently scanning chunks is unsafe, because a credential may cross any chunk boundary; a session carries the boundary state that makes it safe. Limits are mandatory and are counted in UTF-8 bytes:

limits = redact_secret.IncrementalLimits(
    max_input_bytes=1_000_000,
    max_buffered_bytes=32_896,
    max_token_bytes=8_192,
    max_multiline_bytes=32_768,
)

with redact_secret.IncrementalSanitizer(limits) as session:
    first = session.append("api_key=SYNTHETIC_REVOKED_")
    second = session.append("INCREMENTAL_VALUE\nordinary text")
    final = session.finalize()

safe_text = first.text + second.text + final.text
# api_key=<SECRET_1>\nordinary text

Leaving the with block aborts a session that was not finalized, so whatever it still retained is discarded. A session's findings carry absolute code point offsets into the logical whole-session input, so they index "".join(chunks) exactly as the synchronous API's findings index the same joined string.

policy and formatter callbacks receive only normalized safe metadata, never the input or a matched value. A callback that raises, or that returns something other than the documented protocol, never propagates its own error: it becomes one of the fixed SecretScanError subclasses. There is no custom detector callback surface.

The package is typed (PEP 561): the wheel ships py.typed and a _native.pyi stub, so type checkers resolve the API without a stub package.

Supported wheels

Every wheel in that matrix is built and smoke-tested on its own architecture, on CPython 3.10 and 3.14, before a release candidate is accepted; see docs/python-packaging.md.

Building from source

The source distribution needs a Rust toolchain at or above the workspace MSRV (1.88, Rust 2024 edition). With cargo on PATH, pip install builds it like any other source install.

Without one, maturin's build backend downloads a toolchain into a local cache and continues. To refuse that instead and fail immediately with Cargo metadata failed. Do you have cargo in your PATH?, set:

MATURIN_NO_INSTALL_RUST=1 pip install --no-binary redact-secret redact-secret

Set it in any environment that must not fetch a toolchain over the network.

Development

This directory is a mixed Rust/Python maturin project. The crate is redact-secret-python, the native module is redact_secret._native, and the pure Python package lives under python/redact_secret/.

• src/lib.rs owns CPython conversions, Unicode code point range conversion, and the synchronous scan/redact/scan_and_redact API: immutable finding and result types, sanitized exceptions, and the default policy and formatter helpers (decision-define-runtime-bindings).
• src/incremental.rs owns the bounded incremental session: IncrementalSanitizer, its mandatory IncrementalLimits, the lifecycle states, and the incremental policy callback. Its CodePointIndex converts the core's absolute UTF-8 byte offsets to the absolute code point offsets a session reports, by recording only where the input's UTF-8 continuation bytes fall, never the characters themselves. Between successful calls it prunes offsets outside max_buffered_bytes; while processing a call it also indexes the incoming chunk, and its allocation can retain that peak capacity until the session ends. Bound host chunk sizes as well as session limits.
• python/redact_secret/__init__.py re-exports the native module's public surface; python/redact_secret/_native.pyi and py.typed mark the package as typed.
• tests/ runs against a built extension and exercises the shared conformance/ corpus, Unicode code point conversion, callback failure sanitization, placeholder safety, and determinism. The incremental suites add native-string partition invariance (test_incremental_partitions.py), astral character boundaries (test_incremental_unicode.py), and the canonical lifecycle, limit, callback, and failure-cleanup cases (test_incremental.py). They read the corpus from the repository, so they ship with neither the wheel nor the source distribution.
• The extension-module Cargo feature is enabled only by maturin, so the crate still links during cargo test --workspace.

cd bindings/python
python3 -m venv .venv && source .venv/bin/activate
pip install '.[test]' maturin pytest
maturin develop
pytest

Rebuild with maturin develop after any change under src/; pytest imports the installed extension, not the Rust sources.

Packaging identity, the abi3 contract, and the wheel matrix are declared in [workspace.metadata.redact-secret] in the root Cargo.toml and enforced by scripts/check-python-package.py. Build and qualify artifacts with scripts/qualify-python-wheel.py; see docs/python-packaging.md.