simplefix
Simple FIX Protocol implementation for Python
Decision gist · record as of 2026-08-14
Yes. Simplefix is a stable, actively maintained library with no dependencies, permissive licensing, and a clear focus on the narrow problem it solves. Install it if you need to work with FIX messages in Python and want a lightweight alternative to a full FIX engine. Not suitable if you need socket handling, message recovery, or persistence—those require integration with external infrastructure.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Low friction installation as a pure-Python wheel with no runtime dependencies.
- Actively maintained with recent commits and stable production status.
License · maintenance · safety
MIT (permissive) — MIT license permits free use and modification with minimal restrictions, making it suitable for both open-source and commercial projects.
last release 2023-09-12 (1067 days) · last repo commit 2026-06-01 · 255 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 564,380 downloads/mo, #5,977 on PyPI
Alternatives
Verify before relying
pip install simplefix
import simplefix
msg = simplefix.FixMessage()
msg.append_pair(8, 'FIX')
msg.append_pair(35, 'D')
encoded = msg.encode()- Whether the package handles all FIX protocol versions or only a subset
- Performance characteristics for high-throughput message processing
- Support for FIX recovery mechanisms or message persistence features
What it is and what it does
Simplefix is a minimal FIX protocol library that handles the application-layer protocol for financial trading messages. It focuses on message creation, encoding, and parsing without implementing socket handling, recovery, or persistence—those concerns are left to the calling application or a separate FIX engine.
The package provides two main classes: FixMessage for constructing and encoding FIX messages with proper field ordering and checksum calculation, and FixParser for extracting complete messages from byte buffers. It supports standard header tags, UTC timestamp formatting, data fields with length prefixes, and repeating groups. The library is pure Python with no external dependencies and runs on modern Python versions.
Use it for
- Build FIX messages for transmission to trading venues or counterparties in financial applications
- Parse incoming FIX protocol messages from sockets or message queues in trading systems
- Test FIX protocol implementations by creating and validating message structure and encoding
- Integrate FIX protocol support into Python trading algorithms or market data consumers
- Decode FIX messages for logging, monitoring, or audit trails in financial infrastructure
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
Simplefix is a stable, actively maintained library with no dependencies, permissive licensing, and a clear focus on the narrow problem it solves. Install it if you need to work with FIX messages in Python and want a lightweight alternative to a full FIX engine. Not suitable if you need socket handling, message recovery, or persistence—those require integration with external infrastructure.
Install
simplefix on PyPI
Before you install
Low friction installation as a pure-Python wheel with no runtime dependencies. Actively maintained with recent commits and stable production status.
License in practice
MIT license permits free use and modification with minimal restrictions, making it suitable for both open-source and commercial projects.
Quickstart
pip install simplefix
import simplefix
msg = simplefix.FixMessage()
msg.append_pair(8, 'FIX')
msg.append_pair(35, 'D')
encoded = msg.encode()Verify before relying
- Whether the package handles all FIX protocol versions or only a subset
- Performance characteristics for high-throughput message processing
- Support for FIX recovery mechanisms or message persistence features
Package facts
| License | MIT permissive |
| Python support | Not specified |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 1,067 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 564,380 / month, #5,977 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 :: PythonProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Topic :: Software Development :: Libraries :: Python ModulesTopic :: System :: Networking |
Evidence: simplefix-1.0.17-py2.py3-none-any.whl
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