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# Copyright 2024 The etils Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Python utils."""
from __future__ import annotations
from collections.abc import Callable, Sequence
import enum
import functools
import sys
import typing
from typing import Any, Optional, TypeVar, Union
StrOrStrList = Union[str, Sequence[str]]
_Cls = TypeVar('_Cls')
_StrEnum = (
(enum.StrEnum,) if sys.version_info[:2] >= (3, 11) else (str, enum.Enum)
)
class StrEnum(*_StrEnum):
"""Like `Enum`, but `enum.auto()` assigns `str` rather than `int`.
```python
class MyEnum(epy.StrEnum):
SOME_ATTR = enum.auto()
OTHER_ATTR = enum.auto()
assert MyEnum('some_attr') is MyEnum.SOME_ATTR
assert MyEnum.SOME_ATTR == 'some_attr'
```
`StrEnum` is case insensitive.
"""
# `issubclass(StrEnum, str)`, so can annotate `str` instead of `str | StrEnum`
def _generate_next_value_(name, start, count, last_values) -> str: # pylint: disable=no-self-argument
return name.lower()
@classmethod
def _missing_(cls, value: str) -> StrEnum:
if isinstance(value, str) and not value.islower():
return cls(value.lower())
# Could also add `did you meant yy ?`
all_values = [e.value for e in cls]
raise ValueError(
f'{value!r} is not a valid {cls.__qualname__}. '
f'Expected one of {all_values}'
)
def __eq__(self, other: str) -> bool:
return super().__eq__(other.lower())
def __hash__(self) -> int: # pylint: disable=useless-super-delegation
# Somehow `hash` is not defined automatically (maybe because of
# the `__eq__`, so define it explicitly.
return super().__hash__()
# Pytype is confused by EnumMeta.__iter__ vs str.__iter__
if typing.TYPE_CHECKING:
@classmethod
def __iter__(cls):
return type(enum.Enum).__iter__(cls)
def is_namedtuple(x) -> bool:
"""Returns `True` if the value is instance of `NamedTuple`.
This is using some heuristic by checking for a `._field` attribute.
Args:
x: Object to check
Returns:
`True` if the object is a `namedtuple`
"""
return isinstance(x, tuple) and hasattr(type(x), '_fields')
def issubclass_(
cls: Any,
types: Union[type[Any], tuple[type[Any], ...]],
) -> bool:
"""Like `issubclass`, but do not raise error if value is not `type`."""
return isinstance(cls, type) and issubclass(cls, types)
def _wrap_init(init_fn):
"""`__init__` wrapper."""
@functools.wraps(init_fn)
def new_init(self, *args, **kwargs):
# Do NOT use `hasattr` to support children with custom `__getattr__`
if '_epy_is_init_done' in self.__dict__:
# `_epy_is_init_done` already created, so it means we're
# a `super().__init__` call.
return init_fn(self, *args, **kwargs)
object.__setattr__(self, '_epy_is_init_done', False)
init_fn(self, *args, **kwargs)
object.__setattr__(self, '_epy_is_init_done', True)
return new_init
def _wrap_setattr(setattr_fn):
"""`__setattr__` wrapper."""
@functools.wraps(setattr_fn)
def new_setattr(self, name, value):
if not hasattr(self, '_epy_is_init_done'):
raise ValueError(
'Child of `@epy.frozen` class should be `@epy.frozen` too. (Error'
f' raised by {type(self)})'
)
if not self._epy_is_init_done: # pylint: disable=protected-access
return setattr_fn(self, name, value)
else:
raise AttributeError(
f'Cannot assign {name!r} in `@epy.frozen` class {type(self)}'
)
return new_setattr
def frozen(cls: _Cls) -> _Cls:
"""Class decorator which prevent mutating attributes after `__init__`.
Example:
```python
@epy.frozen
class A:
def __init__(self):
self.x = 123
a = A()
a.x = 456 # AttributeError
```
Supports inheritance, child classes should explicitly be marked as
`@epy.frozen` if they mutate additional attributes in `__init__`.
Args:
cls: The class to freeze.
Returns:
cls: The class object
"""
if not isinstance(cls, type):
raise TypeError(f'{cls.__name__} is not')
cls.__init__ = _wrap_init(cls.__init__)
cls.__setattr__ = _wrap_setattr(cls.__setattr__)
return cls
def normalize_str_to_list(x: Optional[StrOrStrList]) -> list[str]:
if x is None:
return []
elif isinstance(x, str):
return [v.strip() for v in x.split(',')]
elif not isinstance(x, (list, tuple)):
raise TypeError(f'Expected list. Got: {x!r}')
else: # list/tuple
return list(x)
def wraps_cls(wrapped: type[Any]) -> Callable[[_Cls], _Cls]:
"""Equivalent of `functools.wraps` but for classes."""
def decorator(cls):
cls.__name__ = wrapped.__name__
cls.__qualname__ = wrapped.__qualname__
cls.__doc__ = wrapped.__doc__
cls.__module__ = wrapped.__module__
return cls
return decorator
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