{"library":"pure-eval","title":"pure-eval","description":"pure-eval is a Python library (current version 0.2.3) designed to safely evaluate Abstract Syntax Tree (AST) nodes without allowing arbitrary code execution or unwanted side effects. It provides a controlled way to inspect and compute values from Python expressions, making it suitable for static analysis and secure evaluation contexts. The library is actively maintained, with updates released periodically.","language":"python","status":"active","last_verified":"Tue May 19","install":{"commands":["pip install pure-eval"],"cli":null},"imports":["from pure_eval import Evaluator","from pure_eval import CannotEval"],"auth":{"required":false,"env_vars":[]},"quickstart":{"code":"import ast\nfrom pure_eval import Evaluator, CannotEval\n\nclass Rectangle:\n    def __init__(self, width, height):\n        self.width = width\n        self.height = height\n        self.area_computed = False\n\n    @property\n    def area(self):\n        self.area_computed = True # This is a side effect\n        return self.width * self.height\n\n# Create an AST node representing a pure expression\nrect_node = ast.parse(\"rect.width * rect.height\").body[0].value\nrect_instance = Rectangle(10, 5)\n\n# Initialize Evaluator with the context. Disable builtins for security.\nevaluator = Evaluator({\n    \"rect\": rect_instance,\n    \"__builtins__\": {} \n})\n\ntry:\n    result = evaluator.evaluate(rect_node)\n    print(f\"Evaluated pure result: {result}\")\nexcept CannotEval as e:\n    print(f\"Could not evaluate pure expression: {e}\")\n\n# Create an AST node representing an expression with a potential side effect\nside_effect_node = ast.parse(\"rect.area\").body[0].value\n\ntry:\n    evaluator.evaluate(side_effect_node)\nexcept CannotEval as e:\n    print(f\"Refused to evaluate expression with potential side effect: {e}\")\n\n# Verify no side effect occurred from the attempted evaluation\nprint(f\"Area computed flag: {rect_instance.area_computed}\")","lang":"python","description":"This example demonstrates how to use `pure-eval` to safely evaluate an AST node representing a pure mathematical expression. It also shows how the library prevents evaluation of expressions that might cause side effects, such as accessing a property that modifies internal state, by raising a `CannotEval` exception. For security, `__builtins__` are explicitly disabled in the evaluator context.","tag":"stale","tag_description":"widespread failures or data too old to trust","last_tested":"2026-04-23","results":[{"runtime":"python:3.10-alpine","exit_code":1},{"runtime":"python:3.10-slim","exit_code":1},{"runtime":"python:3.11-alpine","exit_code":1},{"runtime":"python:3.11-slim","exit_code":1},{"runtime":"python:3.12-alpine","exit_code":1},{"runtime":"python:3.12-slim","exit_code":1},{"runtime":"python:3.13-alpine","exit_code":1},{"runtime":"python:3.13-slim","exit_code":1},{"runtime":"python:3.9-alpine","exit_code":1},{"runtime":"python:3.9-slim","exit_code":1}]},"compatibility":{"tag":"verified","tag_description":"installs cleanly on critical runtimes, fast import, recently 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