File size: 2,198 Bytes
065fee7 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 |
"""
meta.py
Some useful metaclasses.
"""
from __future__ import annotations
from typing import TYPE_CHECKING
if TYPE_CHECKING:
from typing import Any
class LeafClassesMeta(type):
"""
A metaclass for classes that keeps track of all of them that
aren't base classes.
>>> Parent = LeafClassesMeta('MyParentClass', (), {})
>>> Parent in Parent._leaf_classes
True
>>> Child = LeafClassesMeta('MyChildClass', (Parent,), {})
>>> Child in Parent._leaf_classes
True
>>> Parent in Parent._leaf_classes
False
>>> Other = LeafClassesMeta('OtherClass', (), {})
>>> Parent in Other._leaf_classes
False
>>> len(Other._leaf_classes)
1
"""
_leaf_classes: set[type[Any]]
def __init__(
cls,
name: str,
bases: tuple[type[object], ...],
attrs: dict[str, object],
) -> None:
if not hasattr(cls, '_leaf_classes'):
cls._leaf_classes = set()
leaf_classes = getattr(cls, '_leaf_classes')
leaf_classes.add(cls)
# remove any base classes
leaf_classes -= set(bases)
class TagRegistered(type):
"""
As classes of this metaclass are created, they keep a registry in the
base class of all classes by a class attribute, indicated by attr_name.
>>> FooObject = TagRegistered('FooObject', (), dict(tag='foo'))
>>> FooObject._registry['foo'] is FooObject
True
>>> BarObject = TagRegistered('Barobject', (FooObject,), dict(tag='bar'))
>>> FooObject._registry is BarObject._registry
True
>>> len(FooObject._registry)
2
'...' below should be 'jaraco.classes' but for pytest-dev/pytest#3396
>>> FooObject._registry['bar']
<class '....meta.Barobject'>
"""
attr_name = 'tag'
def __init__(
cls,
name: str,
bases: tuple[type[object], ...],
namespace: dict[str, object],
) -> None:
super(TagRegistered, cls).__init__(name, bases, namespace)
if not hasattr(cls, '_registry'):
cls._registry = {}
meta = cls.__class__
attr = getattr(cls, meta.attr_name, None)
if attr:
cls._registry[attr] = cls
|