Evaluate math expressions in Python using whitelisted AST nodes and eval

evaluate.py

import ast
import math

from types import MappingProxyType

_empty_map = MappingProxyType({})

math_locals =  MappingProxyType(
    {name: value for (name, value) in vars(math).items() if not name.startswith('_')} |
    {"abs": abs, "complex": complex, "min": min, "max": max, "pow": pow, "round": round}
)

_whitelist = (
    ast.Module,
    ast.Expr,
    ast.Load,
    ast.Expression,
    ast.Add,
    ast.Sub,
    ast.UnaryOp,
    ast.Num,
    ast.BinOp,
    ast.Mult,
    ast.Div,
    ast.Pow,
    ast.BitOr,
    ast.BitAnd,
    ast.BitXor,
    ast.USub,
    ast.UAdd,
    ast.FloorDiv,
    ast.Mod,
    ast.LShift,
    ast.RShift,
    ast.Invert,
    ast.Call,
    ast.Name,
)

def _only_whitelisted_nodes(root):
    for node in ast.walk(root):
        if not isinstance(node, _whitelist):
            return False

    return True

def evaluate(expr, locals = _empty_map):
    if any(elem in expr for elem in '\n#'):
        raise ValueError(expr) from None

    try:
        node = ast.parse(expr.strip(), mode='eval')
        if not _only_whitelisted_nodes(node):
            raise ValueError(expr) from None
        return eval(compile(node, "<string>", "eval"), {'__builtins__': _empty_map}, locals)

    except (SyntaxError, NameError):
        raise ValueError(expr) from None

if __name__ == "__main__":
    import readline
    from traceback import print_exception

    interactive_locals = {"quit": quit} | math_locals

    while True:
        string = input("⧽⧽⧽ ")
        try:
            value = evaluate(string, locals=interactive_locals)
            interactive_locals["ANS"] = value
            print(value)
        except ValueError as e:
            print_exception(e)