ciso8601

What it is and what it does

ciso8601 is a C extension that converts ISO 8601 and RFC 3339 date-time strings into Python datetime objects. It is designed as a high-performance alternative to pure-Python parsers, with no runtime dependencies beyond Python itself. The library parses a subset of ISO 8601 that covers the most common use cases—basic and extended formats with optional time zone information—and returns either a timezone-aware or naive datetime depending on the input.

The package offers strict error handling: parse_datetime() either returns a valid datetime or raises ValueError with a description of why the string doesn't conform to the supported subset. It is tested across Python 2.7 and 3.4–3.14, though the C extension requires pre-built wheels or a compiler at install time. The documentation notes that since Python 3.11, the built-in datetime module has improved significantly, and ciso8601 may not be necessary for all use cases.

Use it for:

• Parse timestamps in high-throughput APIs or data pipelines where nanosecond-scale performance gains matter.
• Deserialize ISO 8601 timestamps from JSON or other structured data formats in performance-critical applications.
• Handle RFC 3339 timestamps from web services or logs when speed is a requirement.
• Replace slower pure-Python date parsers in existing codebases without changing the calling interface.

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Parses ISO 8601 and RFC 3339 date-time strings into Python datetime objects using a C implementation optimized for speed.

Yes, if you parse ISO 8601 or RFC 3339 strings in a performance-sensitive context and can tolerate the C extension dependency. The compiled wheels cover common platforms, and the library is actively maintained. However, if you're on Python 3.11+ and performance is not critical, the built-in datetime module may be sufficient and simpler. No known security vulnerabilities.

Install

ciso8601 on PyPI

pip install ciso8601

uv add ciso8601

poetry add ciso8601

Installing ciso8601

Before you install

Medium install friction due to compiled C extension requiring platform-specific wheels. Wheels are available for common platforms (macOS, Linux, Windows) across Python 3.10–3.12, but installation may require a C compiler on unsupported architectures. Maintenance is active with recent releases.

License in practice

MIT license is permissive and places no restrictions on use, modification, or distribution in proprietary or open-source projects.

Quickstart

pip install ciso8601

import ciso8601
dt = ciso8601.parse_datetime('2014-12-05T12:30:45.123456-05:30')
print(dt)  # datetime.datetime(2014, 12, 5, 12, 30, 45, 123456, tzinfo=...)

Requires a C compiler or pre-built wheel for your platform; some architectures may not have wheels available.

Verify before relying

• Whether backports.datetime_fromisoformat or the built-in datetime module in Python 3.11+ are sufficient for your use case instead.
• Exact performance gains in your specific workload; benchmarks show nanosecond-scale differences that may not matter outside tight loops.

Package facts

Evidence: ciso8601-2.3.3-cp310-cp310-macosx_11_0_arm64.whl; ciso8601-2.3.3-cp310-cp310-macosx_11_0_universal2.whl; ciso8601-2.3.3-cp310-cp310-macosx_11_0_x86_64.whl; ciso8601-2.3.3-cp310-cp310-manylinux1_x86_64.manylinux_2_28_x86_64.manylinux_2_5_x86_64.whl; ciso8601-2.3.3-cp310-cp310-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; ciso8601-2.3.3-cp310-cp310-musllinux_1_2_aarch64.whl; ciso8601-2.3.3-cp310-cp310-musllinux_1_2_x86_64.whl; ciso8601-2.3.3-cp310-cp310-win_amd64.whl; ciso8601-2.3.3-cp311-cp311-macosx_11_0_arm64.whl; ciso8601-2.3.3-cp311-cp311-macosx_11_0_universal2.whl; ciso8601-2.3.3-cp311-cp311-macosx_11_0_x86_64.whl; ciso8601-2.3.3-cp311-cp311-manylinux1_x86_64.manylinux_2_28_x86_64.manylinux_2_5_x86_64.whl; ciso8601-2.3.3-cp311-cp311-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; ciso8601-2.3.3-cp311-cp311-musllinux_1_2_aarch64.whl; ciso8601-2.3.3-cp311-cp311-musllinux_1_2_x86_64.whl; ciso8601-2.3.3-cp311-cp311-win_amd64.whl; ciso8601-2.3.3-cp312-cp312-macosx_11_0_arm64.whl; ciso8601-2.3.3-cp312-cp312-macosx_11_0_universal2.whl; ciso8601-2.3.3-cp312-cp312-macosx_11_0_x86_64.whl; ciso8601-2.3.3-cp312-cp312-manylinux1_x86_64.manylinux_2_28_x86_64.manylinux_2_5_x86_64.whl

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