diff options
Diffstat (limited to 'venv/lib/python3.8/site-packages/blinker/_utilities.py')
-rw-r--r-- | venv/lib/python3.8/site-packages/blinker/_utilities.py | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/venv/lib/python3.8/site-packages/blinker/_utilities.py b/venv/lib/python3.8/site-packages/blinker/_utilities.py new file mode 100644 index 0000000..000c902 --- /dev/null +++ b/venv/lib/python3.8/site-packages/blinker/_utilities.py @@ -0,0 +1,64 @@ +from __future__ import annotations + +import collections.abc as c +import inspect +import typing as t +from weakref import ref +from weakref import WeakMethod + +T = t.TypeVar("T") + + +class Symbol: + """A constant symbol, nicer than ``object()``. Repeated calls return the + same instance. + + >>> Symbol('foo') is Symbol('foo') + True + >>> Symbol('foo') + foo + """ + + symbols: t.ClassVar[dict[str, Symbol]] = {} + + def __new__(cls, name: str) -> Symbol: + if name in cls.symbols: + return cls.symbols[name] + + obj = super().__new__(cls) + cls.symbols[name] = obj + return obj + + def __init__(self, name: str) -> None: + self.name = name + + def __repr__(self) -> str: + return self.name + + def __getnewargs__(self) -> tuple[t.Any, ...]: + return (self.name,) + + +def make_id(obj: object) -> c.Hashable: + """Get a stable identifier for a receiver or sender, to be used as a dict + key or in a set. + """ + if inspect.ismethod(obj): + # The id of a bound method is not stable, but the id of the unbound + # function and instance are. + return id(obj.__func__), id(obj.__self__) + + if isinstance(obj, (str, int)): + # Instances with the same value always compare equal and have the same + # hash, even if the id may change. + return obj + + # Assume other types are not hashable but will always be the same instance. + return id(obj) + + +def make_ref(obj: T, callback: c.Callable[[ref[T]], None] | None = None) -> ref[T]: + if inspect.ismethod(obj): + return WeakMethod(obj, callback) # type: ignore[arg-type, return-value] + + return ref(obj, callback) |