function.py 文件源码

def eval_function_def_as_closure(function_def, closure_names, globals_=None, flags=None):
    """
    Evaluates an AST of a function definition inside a closure with the variables
    from ``closure_names`` set to ``None``, and an optional dictionary of globals.
    Returns a callable function (a ``types.FunctionType`` object).

    .. warning::

        Before the returned function can be actually called, the "fake" closure cells
        (filled with ``None``) must be substituted by actual closure cells
        that will be used during the call.
    """

    assert type(function_def) == ast.FunctionDef
    none = ast.NameConstant(value=None)

    # We can't possibly recreate ASTs of existing closure variables
    # (because all we have are their values).
    # So we create fake closure variables for the function to attach to,
    # and then substitute the closure cells with the ones obtained from
    # the "prototype" of this function (a ``types.FunctionType`` object
    # from which this tree was extracted).
    fake_closure_vars = [
        ast.Assign(
            targets=[ast.Name(id=name, ctx=ast.Store())],
            value=none)
        for name in closure_names]

    empty_args = ast.arguments(
        args=[],
        vararg=None,
        kwonlyargs=[],
        kwarg=None,
        defaults=[],
        kw_defaults=[])

    wrapper_def = ast.FunctionDef(
        name='__peval_wrapper',
        args=empty_args,
        decorator_list=[],
        body=(
            fake_closure_vars +
            [function_def] +
            [ast.Return(value=ast.Name(id=function_def.name, ctx=ast.Load()))]))

    wrapper = eval_function_def(wrapper_def, globals_=globals_, flags=flags)
    return wrapper()