calc.py 文件源码

def calculate(
    expr: str,
    *,
    replace_num_to_decimal: bool=True
):
    node = ast.parse(expr, filename='<ast>', mode='exec')
    local: Dict[str, Any] = {}

    if replace_num_to_decimal:
        Transformer().visit(node)
        ast.fix_missing_locations(node)

    en = ExtractNames()
    en.visit(node)
    names = en.names

    if '__result__' in names:
        raise SyntaxError('assign __result__ value is not allowed.')

    Validator(names).visit(node)
    last = node.body[-1]
    expect_result = False
    result = None
    if isinstance(last, TYPE_EXPR):
        expect_result = True
        node.body[-1] = ast.Assign(
            targets=[ast.Name(id='__result__', ctx=ast.Store())],
            value=last.value
        )
        ast.fix_missing_locations(node)

    exec(compile(node, filename='<ast>', mode='exec'), GLOBAL_CONTEXT, local)

    if expect_result:
        result = local['__result__']
        del local['__result__']

    if isinstance(result, Iterable) and \
       not isinstance(result, BUILTIN_ITERABLE):
        result = list(result)

    return result, local