starlark-go 1.1.0rc1

Python bindings for the Go implementation of Starlark

python-starlark-go

Introduction

This module provides Python bindings for the Starlark programming language.

Starlark is a dialect of Python designed for hermetic execution and deterministic evaluation. That means you can run Starlark code you don't trust without worrying about it being able access any data you did not explicitly supply to it, and that you can count on the same code to always produce the same value when used with the same input data. Starlark was originally created for the Bazel build system. There are now several implementations of Starlark; this module is built on starlark-go.

This module was originally forked from Kevin Chung's pystarlark.

The version of starlark-go that is currently embedded in this module is v0.0.0-20230302034142-4b1e35fe2254.

Features

• Evalutes Starlark code from Python
• Translates Starlark exceptions to Python exceptions
• Converts Starlark values to Python values
• Converts Python values to Starlark values
• No runtime dependencies - cgo is used to bundle starlark-go into a Python extension

Installation

pip install starlark-go

Usage

from starlark_go import Starlark

s = Starlark()
fibonacci = """
def fibonacci(n=10):
   res = list(range(n))
   for i in res[2:]:
       res[i] = res[i-2] + res[i-1]
   return res
"""
s.exec(fibonacci)
s.eval("fibonacci(5)")  # [0, 1, 1, 2, 3]

s.set(x=5)
s.eval("x") # 5
s.eval("fibonacci(x)")  # [0, 1, 1, 2, 3]

Caveats

Avoid replacing the same Starlark global variable with a different function. This will leak a small amount of memory. Continued redefinition of the variable will cause more memory leaks. PRs welcome to fix this.