PyYAML-ft
YAML parser and emitter for Python with support for free-threading
Decision gist · record as of 2026-08-14
Yes, if you are running Python 3.13 or 3.13t and need YAML processing in a multi-threaded application. The aging maintenance status (430 days since last release) is acceptable given the package's stated purpose as a temporary fork pending upstream support; however, verify that Cython 3.1's free-threading support is stable enough for your workload. For Python < 3.13, use upstream PyYAML instead.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.13 or 3.13t (free-threaded build); will not install on earlier Python versions.
- Medium install friction due to compiled C extensions.
- The package is aging—last release was 430 days ago—but the repository remains active with a recent commit on 2025-06-10.
License · maintenance · safety
MIT (permissive) — MIT license is permissive, allowing commercial and private use with minimal restrictions. No licensing friction for most projects.
last release 2025-06-10 (430 days) · last repo commit 2025-06-10 · 1 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 10,219,784 downloads/mo, #1,467 on PyPI
Alternatives
Verify before relying
pip install PyYAML-ft
import PyYAML-ft
data = PyYAML-ft.safe_load('key: value')
print(data)- Whether LibYAML bindings are reliably available on all supported platforms or fall back silently.
- Performance characteristics compared to upstream PyYAML when running on free-threaded Python 3.13.
- Stability of Cython 3.1 support for free-threading in production workloads.
- Thread-local registry behavior and whether re-registration per thread is required for custom constructors.
What it is and what it does
PyYAML-ft is a fork of PyYAML designed specifically for Python 3.13's free-threaded build. It provides YAML parsing and serialization with thread-local registries for custom constructors, representers, and resolvers—meaning these must be registered per-thread rather than globally. The package uses Cython 3.1 (still experimental) and optionally compiles against LibYAML for faster C-based parsing and emission.
The main trade-off is that custom YAML handlers registered in one thread are not automatically available in others; you must re-register them in each thread's worker function. This is a deliberate design choice to avoid thread-safety issues that the GIL previously masked. For applications using only built-in YAML types, the API is identical to upstream PyYAML.
Use it for
- Parse YAML configuration files in multi-threaded Python 3.13 applications without GIL contention.
- Serialize Python objects to YAML in free-threaded environments where concurrent dumping is needed.
- Test upstream PyYAML behavior under free-threading before the official port is merged.
- Build thread-pool-based services that load YAML documents concurrently on Python 3.13t.
- Use safe_load() for untrusted YAML input in multi-threaded contexts without thread-safety concerns.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you are running Python 3.13 or 3.13t and need YAML processing in a multi-threaded application.
The aging maintenance status (430 days since last release) is acceptable given the package's stated purpose as a temporary fork pending upstream support; however, verify that Cython 3.1's free-threading support is stable enough for your workload. For Python < 3.13, use upstream PyYAML instead.
Install
pyyaml-ft on PyPI
Before you install
Medium install friction due to compiled C extensions. The package is aging—last release was 430 days ago—but the repository remains active with a recent commit on 2025-06-10. No runtime dependencies simplifies deployment once installed.
Requires Python 3.13 or 3.13t (free-threaded build); will not install on earlier Python versions.
License in practice
MIT license is permissive, allowing commercial and private use with minimal restrictions. No licensing friction for most projects.
Quickstart
pip install PyYAML-ft
import PyYAML-ft
data = PyYAML-ft.safe_load('key: value')
print(data)Verify before relying
- Whether LibYAML bindings are reliably available on all supported platforms or fall back silently.
- Performance characteristics compared to upstream PyYAML when running on free-threaded Python 3.13.
- Stability of Cython 3.1 support for free-threading in production workloads.
- Thread-local registry behavior and whether re-registration per thread is required for custom constructors.
Package facts
| License | MIT permissive |
| Python support | Supports the current Python release >=3.13 |
| Install friction | Medium. Platform-specific wheel |
| Runtime dependencies | None |
| Maintenance | Aging 430 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 10,219,784 / month, #1,467 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableIntended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseOperating System :: OS IndependentProgramming Language :: CythonProgramming Language :: PythonProgramming Language :: Python :: 3.13Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: Software Development :: Libraries :: Python ModulesTopic :: Text Processing :: Markup |
Evidence: pyyaml_ft-8.0.0-cp313-cp313-macosx_10_13_x86_64.whl; pyyaml_ft-8.0.0-cp313-cp313-macosx_11_0_arm64.whl; pyyaml_ft-8.0.0-cp313-cp313-manylinux_2_17_aarch64.manylinux2014_aarch64.whl; pyyaml_ft-8.0.0-cp313-cp313-manylinux_2_17_s390x.manylinux2014_s390x.whl; pyyaml_ft-8.0.0-cp313-cp313-manylinux_2_17_x86_64.manylinux2014_x86_64.whl; pyyaml_ft-8.0.0-cp313-cp313-musllinux_1_2_aarch64.whl; pyyaml_ft-8.0.0-cp313-cp313-musllinux_1_2_x86_64.whl; pyyaml_ft-8.0.0-cp313-cp313t-macosx_10_13_x86_64.whl; pyyaml_ft-8.0.0-cp313-cp313t-macosx_11_0_arm64.whl; pyyaml_ft-8.0.0-cp313-cp313t-manylinux_2_17_aarch64.manylinux2014_aarch64.whl; pyyaml_ft-8.0.0-cp313-cp313t-manylinux_2_17_s390x.manylinux2014_s390x.whl; pyyaml_ft-8.0.0-cp313-cp313t-manylinux_2_17_x86_64.manylinux2014_x86_64.whl; pyyaml_ft-8.0.0-cp313-cp313t-musllinux_1_2_aarch64.whl; pyyaml_ft-8.0.0-cp313-cp313t-musllinux_1_2_x86_64.whl; pyyaml_ft-8.0.0-cp313-cp313t-win_amd64.whl; pyyaml_ft-8.0.0-cp313-cp313-win_amd64.whl
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