param
Declarative parameters for robust Python classes and a rich API for reactive programming
Decision gist · record as of 2026-08-14
Yes. Param is production-stable, actively maintained, has zero runtime dependencies, and solves a real problem: combining declarative attribute validation with reactive programming. Install it if you need runtime parameter validation with class-level configuration, or if you're building interactive systems where automatic synchronization matters. The BSD-3-Clause license poses no barrier.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.10 or later.
- Installation is straightforward with zero runtime dependencies and a pure Python wheel.
- The package is actively maintained with recent releases and a stable codebase.
License · maintenance · safety
BSD-3-Clause (permissive) — BSD-3-Clause is a permissive license allowing commercial and private use with minimal restrictions, making it suitable for most projects.
last release 2026-06-09 (66 days) · last repo commit 2026-08-12 · 520 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 2,798,370 downloads/mo, #2,883 on PyPI
Alternatives
Verify before relying
import param
class MyClass(param.Parameterized):
value = param.Integer(default=5, bounds=(0, 10))
name = param.String(default='test')
obj = MyClass(value=7)
print(obj.param.values())- Whether reactive watchers scale well with hundreds or thousands of interdependent parameters.
- Performance characteristics when used in high-frequency update scenarios.
- Integration patterns with async/await code.
What it is and what it does
Param is a zero-dependency library for building classes with rich, validated attributes and reactive programming capabilities. You define attributes as Parameter objects—Integer, String, Selector, Event, and many others—each with metadata like bounds, default values, documentation, and nullability constraints. Param enforces these constraints at runtime, raising errors when invalid values are assigned. The library also provides a reactive API: you can declare that methods should automatically run when specific attributes change, enabling data-driven workflows where UI updates, computations, or side effects trigger automatically.
Param serves as the foundation for HoloViz's Panel and HoloViews libraries, which rely on its combination of declarative attributes and reactive bindings to power interactive visualizations and responsive applications. It is conceptually similar to Pydantic or dataclasses but emphasizes class-level attribute configuration, parameter inheritance across subclasses, and automatic reactivity rather than just input validation.
Use it for
- Build configuration classes with validated, documented parameters that can be introspected by tools to generate UIs or CLIs automatically.
- Create interactive applications where method calls or state updates trigger automatically when watched parameters change.
- Define hierarchies of classes where subclasses inherit and selectively override parameter metadata from parent classes.
- Implement data pipelines where reactive dependencies ensure downstream computations stay synchronized with upstream changes.
- Construct scientific or data-analysis workflows with rich parameter metadata for reproducibility and documentation.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
Param is production-stable, actively maintained, has zero runtime dependencies, and solves a real problem: combining declarative attribute validation with reactive programming. Install it if you need runtime parameter validation with class-level configuration, or if you're building interactive systems where automatic synchronization matters. The BSD-3-Clause license poses no barrier.
Install
param on PyPI
Before you install
Installation is straightforward with zero runtime dependencies and a pure Python wheel. The package is actively maintained with recent releases and a stable codebase.
Requires Python 3.10 or later.
License in practice
BSD-3-Clause is a permissive license allowing commercial and private use with minimal restrictions, making it suitable for most projects.
Quickstart
import param
class MyClass(param.Parameterized):
value = param.Integer(default=5, bounds=(0, 10))
name = param.String(default='test')
obj = MyClass(value=7)
print(obj.param.values())Verify before relying
- Whether reactive watchers scale well with hundreds or thousands of interdependent parameters.
- Performance characteristics when used in high-frequency update scenarios.
- Integration patterns with async/await code.
Package facts
| License | BSD-3-Clause permissive |
| Python support | Supports the current Python release >=3.10 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 66 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 2,798,370 / month, #2,883 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 :: DevelopersIntended Audience :: Science/ResearchLicense :: OSI Approved :: BSD LicenseNatural Language :: EnglishOperating System :: OS IndependentProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Topic :: Scientific/EngineeringTopic :: Software Development :: LibrariesTyping :: Typed |
Evidence: param-2.4.1-py3-none-any.whl
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See also overrides · redis-om · argparse-dataclass · parameterized · annotated-types · docsig · unittest-parametrize · inject · magic-filter · uipath-runtime