cloud-custodian/cel-python

cel-python is a pure Python implementation of the Common Expression Language that enables expression evaluation across different applications and platforms.

CEL addresses the need for a common expression language that allows organizations with complex infrastructure to reason about their systems consistently and enables interoperability across programming languages and platforms. This implementation provides a minimal-dependency runtime that can be embedded directly into Python applications. It includes support for re2 regular expression syntax as specified by CEL, and offers both a command-line interface for ad-hoc evaluation and a library API for programmatic use. The library follows a multi-step compilation pattern where expressions are first compiled to an abstract syntax tree, then converted to a runnable program that can be evaluated against provided context data.

The tool suits Python-based applications that need to evaluate expressions safely without exposing the full power of Python's execution model. It is particularly valuable for security policy evaluation and rule-based decision-making in cloud infrastructure contexts. The command-line interface makes it useful for quick calculations and JSON filtering tasks similar to tools like jq or expr. Organizations building policy engines or security filters benefit from CEL's standardized semantics, which ensure consistent behavior across different implementations and platforms.

The project maintains active continuous integration workflows and publishes releases to package repositories. Development activity shows ongoing attention to core functionality and dependency management, including integration of the Google-RE2 module for standards-compliant regular expression handling.