v0.7.0

Python CEL 0.7.0 gives you a much bigger built-in toolbox, lets you call your own functions as methods, and can tell you what an expression uses before you run it — on top of a refreshed, more secure Rust core.

✨ What's new

An extended standard library — dozens of functions matching Google's cel-go, opt-in via cel.stdlib:

import cel
from cel.stdlib import add_stdlib_to_context

ctx = cel.Context()
add_stdlib_to_context(ctx)

cel.evaluate('"Hello World".lowerAscii()', ctx)   # 'hello world'
cel.evaluate("math.greatest([3, 1, 2])", ctx)     # 3
cel.evaluate("[1, 1, 2, 3].distinct()", ctx)      # [1, 2, 3]
cel.evaluate('base64.encode(b"hi")', ctx)         # 'aGk='

Covers strings, math, sets, encoders and lists helpers (plus bool/dyn/type/min/max). The cel command-line tool enables them automatically.

Call custom functions as methods — a function you register works as both f(x) and x.f(y):

ctx = cel.Context()
ctx.add_function("shout", lambda s: s.upper() + "!")
cel.evaluate('"hi".shout()', ctx)   # 'HI!'

Inspect an expression before running it — see which variables and functions it references:

program = cel.compile("user.age >= min_age && size(roles) > 0")
program.variables()   # ['min_age', 'roles', 'user']
program.functions()   # ['_&&_', '_>=_', '_>_', 'size']

Handy for validating that your context supplies everything an expression needs, or restricting which names an expression may touch.

⚡ Under the hood

• Upgraded to cel-rust 0.14 — faster and more spec-compliant.
• Upgraded to PyO3 0.29, which pulls in upstream security fixes.
• Clearer, more Pythonic error messages (e.g. TypeError: Unsupported operation: string + int).

⚠️ Heads up — behaviour changes

These come from cel 0.14 and may affect existing expressions:

• contains is now string-only. Use the in operator for membership — 2 in [1, 2, 3], "key" in myMap — or enable the lists extension to get .contains() back for lists and maps.
• min/max moved into the opt-in cel.stdlib core extension (they used to be always available).
• Built-in functions take precedence over a custom function registered with the same name.

📦 Install / upgrade

pip install --upgrade common-expression-language

See the CHANGELOG for the complete list of changes, and the docs for the new standard-library and introspection reference.