structured_data._cant_modify

Complexity

Total Complexity

4

Size/Duplication

Total Lines	24
Duplicated Lines	0 %

Importance

Changes

0

2 Functions

Rating	Name	Duplication	Size	Complexity
A	guard()	0	4	2
A	cant_modify()	0	9	2

"""Helper funtion for common pseudo-immutable use case."""

import inspect
import typing

MISSING = object()


def cant_modify(self: typing.Any, name: str) -> None:
    """Prevent attempts to modify an attr of the given name."""
    class_repr = repr(self.__class__.__name__)
    name_repr = repr(name)
    if inspect.getattr_static(self, name, MISSING) is MISSING:
        format_msg = "{class_repr} object has no attribute {name_repr}"
    else:
        format_msg = "{class_repr} object attribute {name_repr} is read-only"
    raise AttributeError(format_msg.format(class_repr=class_repr, name_repr=name_repr))


def guard(instance: typing.Any, name: str) -> None:
    """Wrap up the common logic for using cant_modify."""
    if not inspect.isdatadescriptor(inspect.getattr_static(instance, name, MISSING)):
        cant_modify(instance, name)