# SPDX-License-Identifier: MIT """ These are keyword-only APIs that call `attr.s` and `attr.ib` with different default values. """ from functools import partial from . import setters from ._funcs import asdict as _asdict from ._funcs import astuple as _astuple from ._make import ( _DEFAULT_ON_SETATTR, NOTHING, _frozen_setattrs, attrib, attrs, ) from .exceptions import UnannotatedAttributeError def define( maybe_cls=None, *, these=None, repr=None, unsafe_hash=None, hash=None, init=None, slots=True, frozen=False, weakref_slot=True, str=False, auto_attribs=None, kw_only=False, cache_hash=False, auto_exc=True, eq=None, order=False, auto_detect=True, getstate_setstate=None, on_setattr=None, field_transformer=None, match_args=True, ): r""" A class decorator that adds :term:`dunder methods` according to :term:`fields ` specified using :doc:`type annotations `, `field()` calls, or the *these* argument. Since *attrs* patches or replaces an existing class, you cannot use `object.__init_subclass__` with *attrs* classes, because it runs too early. As a replacement, you can define ``__attrs_init_subclass__`` on your class. It will be called by *attrs* classes that subclass it after they're created. See also :ref:`init-subclass`. Args: slots (bool): Create a :term:`slotted class ` that's more memory-efficient. Slotted classes are generally superior to the default dict classes, but have some gotchas you should know about, so we encourage you to read the :term:`glossary entry `. auto_detect (bool): Instead of setting the *init*, *repr*, *eq*, and *hash* arguments explicitly, assume they are set to True **unless any** of the involved methods for one of the arguments is implemented in the *current* class (meaning, it is *not* inherited from some base class). So, for example by implementing ``__eq__`` on a class yourself, *attrs* will deduce ``eq=False`` and will create *neither* ``__eq__`` *nor* ``__ne__`` (but Python classes come with a sensible ``__ne__`` by default, so it *should* be enough to only implement ``__eq__`` in most cases). Passing True or False` to *init*, *repr*, *eq*, *cmp*, or *hash* overrides whatever *auto_detect* would determine. auto_exc (bool): If the class subclasses `BaseException` (which implicitly includes any subclass of any exception), the following happens to behave like a well-behaved Python exception class: - the values for *eq*, *order*, and *hash* are ignored and the instances compare and hash by the instance's ids [#]_ , - all attributes that are either passed into ``__init__`` or have a default value are additionally available as a tuple in the ``args`` attribute, - the value of *str* is ignored leaving ``__str__`` to base classes. .. [#] Note that *attrs* will *not* remove existing implementations of ``__hash__`` or the equality methods. It just won't add own ones. on_setattr (~typing.Callable | list[~typing.Callable] | None | ~typing.Literal[attrs.setters.NO_OP]): A callable that is run whenever the user attempts to set an attribute (either by assignment like ``i.x = 42`` or by using `setattr` like ``setattr(i, "x", 42)``). It receives the same arguments as validators: the instance, the attribute that is being modified, and the new value. If no exception is raised, the attribute is set to the return value of the callable. If a list of callables is passed, they're automatically wrapped in an `attrs.setters.pipe`. If left None, the default behavior is to run converters and validators whenever an attribute is set. init (bool): Create a ``__init__`` method that initializes the *attrs* attributes. Leading underscores are stripped for the argument name, unless an alias is set on the attribute. .. seealso:: `init` shows advanced ways to customize the generated ``__init__`` method, including executing code before and after. repr(bool): Create a ``__repr__`` method with a human readable representation of *attrs* attributes. str (bool): Create a ``__str__`` method that is identical to ``__repr__``. This is usually not necessary except for `Exception`\ s. eq (bool | None): If True or None (default), add ``__eq__`` and ``__ne__`` methods that check two instances for equality. .. seealso:: `comparison` describes how to customize the comparison behavior going as far comparing NumPy arrays. order (bool | None): If True, add ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` methods that behave like *eq* above and allow instances to be ordered. They compare the instances as if they were tuples of their *attrs* attributes if and only if the types of both classes are *identical*. If `None` mirror value of *eq*. .. seealso:: `comparison` cmp (bool | None): Setting *cmp* is equivalent to setting *eq* and *order* to the same value. Must not be mixed with *eq* or *order*. unsafe_hash (bool | None): If None (default), the ``__hash__`` method is generated according how *eq* and *frozen* are set. 1. If *both* are True, *attrs* will generate a ``__hash__`` for you. 2. If *eq* is True and *frozen* is False, ``__hash__`` will be set to None, marking it unhashable (which it is). 3. If *eq* is False, ``__hash__`` will be left untouched meaning the ``__hash__`` method of the base class will be used. If the base class is `object`, this means it will fall back to id-based hashing. Although not recommended, you can decide for yourself and force *attrs* to create one (for example, if the class is immutable even though you didn't freeze it programmatically) by passing True or not. Both of these cases are rather special and should be used carefully. .. seealso:: - Our documentation on `hashing`, - Python's documentation on `object.__hash__`, - and the `GitHub issue that led to the default \ behavior `_ for more details. hash (bool | None): Deprecated alias for *unsafe_hash*. *unsafe_hash* takes precedence. cache_hash (bool): Ensure that the object's hash code is computed only once and stored on the object. If this is set to True, hashing must be either explicitly or implicitly enabled for this class. If the hash code is cached, avoid any reassignments of fields involved in hash code computation or mutations of the objects those fields point to after object creation. If such changes occur, the behavior of the object's hash code is undefined. frozen (bool): Make instances immutable after initialization. If someone attempts to modify a frozen instance, `attrs.exceptions.FrozenInstanceError` is raised. .. note:: 1. This is achieved by installing a custom ``__setattr__`` method on your class, so you can't implement your own. 2. True immutability is impossible in Python. 3. This *does* have a minor a runtime performance `impact ` when initializing new instances. In other words: ``__init__`` is slightly slower with ``frozen=True``. 4. If a class is frozen, you cannot modify ``self`` in ``__attrs_post_init__`` or a self-written ``__init__``. You can circumvent that limitation by using ``object.__setattr__(self, "attribute_name", value)``. 5. Subclasses of a frozen class are frozen too. kw_only (bool): Make all attributes keyword-only in the generated ``__init__`` (if *init* is False, this parameter is ignored). weakref_slot (bool): Make instances weak-referenceable. This has no effect unless *slots* is True. field_transformer (~typing.Callable | None): A function that is called with the original class object and all fields right before *attrs* finalizes the class. You can use this, for example, to automatically add converters or validators to fields based on their types. .. seealso:: `transform-fields` match_args (bool): If True (default), set ``__match_args__`` on the class to support :pep:`634` (*Structural Pattern Matching*). It is a tuple of all non-keyword-only ``__init__`` parameter names on Python 3.10 and later. Ignored on older Python versions. collect_by_mro (bool): If True, *attrs* collects attributes from base classes correctly according to the `method resolution order `_. If False, *attrs* will mimic the (wrong) behavior of `dataclasses` and :pep:`681`. See also `issue #428 `_. getstate_setstate (bool | None): .. note:: This is usually only interesting for slotted classes and you should probably just set *auto_detect* to True. If True, ``__getstate__`` and ``__setstate__`` are generated and attached to the class. This is necessary for slotted classes to be pickleable. If left None, it's True by default for slotted classes and False for dict classes. If *auto_detect* is True, and *getstate_setstate* is left None, and **either** ``__getstate__`` or ``__setstate__`` is detected directly on the class (meaning: not inherited), it is set to False (this is usually what you want). auto_attribs (bool | None): If True, look at type annotations to determine which attributes to use, like `dataclasses`. If False, it will only look for explicit :func:`field` class attributes, like classic *attrs*. If left None, it will guess: 1. If any attributes are annotated and no unannotated `attrs.field`\ s are found, it assumes *auto_attribs=True*. 2. Otherwise it assumes *auto_attribs=False* and tries to collect `attrs.field`\ s. If *attrs* decides to look at type annotations, **all** fields **must** be annotated. If *attrs* encounters a field that is set to a :func:`field` / `attr.ib` but lacks a type annotation, an `attrs.exceptions.UnannotatedAttributeError` is raised. Use ``field_name: typing.Any = field(...)`` if you don't want to set a type. .. warning:: For features that use the attribute name to create decorators (for example, :ref:`validators `), you still *must* assign :func:`field` / `attr.ib` to them. Otherwise Python will either not find the name or try to use the default value to call, for example, ``validator`` on it. Attributes annotated as `typing.ClassVar`, and attributes that are neither annotated nor set to an `field()` are **ignored**. these (dict[str, object]): A dictionary of name to the (private) return value of `field()` mappings. This is useful to avoid the definition of your attributes within the class body because you can't (for example, if you want to add ``__repr__`` methods to Django models) or don't want to. If *these* is not `None`, *attrs* will *not* search the class body for attributes and will *not* remove any attributes from it. The order is deduced from the order of the attributes inside *these*. Arguably, this is a rather obscure feature. .. versionadded:: 20.1.0 .. versionchanged:: 21.3.0 Converters are also run ``on_setattr``. .. versionadded:: 22.2.0 *unsafe_hash* as an alias for *hash* (for :pep:`681` compliance). .. versionchanged:: 24.1.0 Instances are not compared as tuples of attributes anymore, but using a big ``and`` condition. This is faster and has more correct behavior for uncomparable values like `math.nan`. .. versionadded:: 24.1.0 If a class has an *inherited* classmethod called ``__attrs_init_subclass__``, it is executed after the class is created. .. deprecated:: 24.1.0 *hash* is deprecated in favor of *unsafe_hash*. .. note:: The main differences to the classic `attr.s` are: - Automatically detect whether or not *auto_attribs* should be `True` (c.f. *auto_attribs* parameter). - Converters and validators run when attributes are set by default -- if *frozen* is `False`. - *slots=True* Usually, this has only upsides and few visible effects in everyday programming. But it *can* lead to some surprising behaviors, so please make sure to read :term:`slotted classes`. - *auto_exc=True* - *auto_detect=True* - *order=False* - Some options that were only relevant on Python 2 or were kept around for backwards-compatibility have been removed. """ def do_it(cls, auto_attribs): return attrs( maybe_cls=cls, these=these, repr=repr, hash=hash, unsafe_hash=unsafe_hash, init=init, slots=slots, frozen=frozen, weakref_slot=weakref_slot, str=str, auto_attribs=auto_attribs, kw_only=kw_only, cache_hash=cache_hash, auto_exc=auto_exc, eq=eq, order=order, auto_detect=auto_detect, collect_by_mro=True, getstate_setstate=getstate_setstate, on_setattr=on_setattr, field_transformer=field_transformer, match_args=match_args, ) def wrap(cls): """ Making this a wrapper ensures this code runs during class creation. We also ensure that frozen-ness of classes is inherited. """ nonlocal frozen, on_setattr had_on_setattr = on_setattr not in (None, setters.NO_OP) # By default, mutable classes convert & validate on setattr. if frozen is False and on_setattr is None: on_setattr = _DEFAULT_ON_SETATTR # However, if we subclass a frozen class, we inherit the immutability # and disable on_setattr. for base_cls in cls.__bases__: if base_cls.__setattr__ is _frozen_setattrs: if had_on_setattr: msg = "Frozen classes can't use on_setattr (frozen-ness was inherited)." raise ValueError(msg) on_setattr = setters.NO_OP break if auto_attribs is not None: return do_it(cls, auto_attribs) try: return do_it(cls, True) except UnannotatedAttributeError: return do_it(cls, False) # maybe_cls's type depends on the usage of the decorator. It's a class # if it's used as `@attrs` but `None` if used as `@attrs()`. if maybe_cls is None: return wrap return wrap(maybe_cls) mutable = define frozen = partial(define, frozen=True, on_setattr=None) def field( *, default=NOTHING, validator=None, repr=True, hash=None, init=True, metadata=None, type=None, converter=None, factory=None, kw_only=False, eq=None, order=None, on_setattr=None, alias=None, ): """ Create a new :term:`field` / :term:`attribute` on a class. .. warning:: Does **nothing** unless the class is also decorated with `attrs.define` (or similar)! Args: default: A value that is used if an *attrs*-generated ``__init__`` is used and no value is passed while instantiating or the attribute is excluded using ``init=False``. If the value is an instance of `attrs.Factory`, its callable will be used to construct a new value (useful for mutable data types like lists or dicts). If a default is not set (or set manually to `attrs.NOTHING`), a value *must* be supplied when instantiating; otherwise a `TypeError` will be raised. .. seealso:: `defaults` factory (~typing.Callable): Syntactic sugar for ``default=attr.Factory(factory)``. validator (~typing.Callable | list[~typing.Callable]): Callable that is called by *attrs*-generated ``__init__`` methods after the instance has been initialized. They receive the initialized instance, the :func:`~attrs.Attribute`, and the passed value. The return value is *not* inspected so the validator has to throw an exception itself. If a `list` is passed, its items are treated as validators and must all pass. Validators can be globally disabled and re-enabled using `attrs.validators.get_disabled` / `attrs.validators.set_disabled`. The validator can also be set using decorator notation as shown below. .. seealso:: :ref:`validators` repr (bool | ~typing.Callable): Include this attribute in the generated ``__repr__`` method. If True, include the attribute; if False, omit it. By default, the built-in ``repr()`` function is used. To override how the attribute value is formatted, pass a ``callable`` that takes a single value and returns a string. Note that the resulting string is used as-is, which means it will be used directly *instead* of calling ``repr()`` (the default). eq (bool | ~typing.Callable): If True (default), include this attribute in the generated ``__eq__`` and ``__ne__`` methods that check two instances for equality. To override how the attribute value is compared, pass a callable that takes a single value and returns the value to be compared. .. seealso:: `comparison` order (bool | ~typing.Callable): If True (default), include this attributes in the generated ``__lt__``, ``__le__``, ``__gt__`` and ``__ge__`` methods. To override how the attribute value is ordered, pass a callable that takes a single value and returns the value to be ordered. .. seealso:: `comparison` cmp(bool | ~typing.Callable): Setting *cmp* is equivalent to setting *eq* and *order* to the same value. Must not be mixed with *eq* or *order*. .. seealso:: `comparison` hash (bool | None): Include this attribute in the generated ``__hash__`` method. If None (default), mirror *eq*'s value. This is the correct behavior according the Python spec. Setting this value to anything else than None is *discouraged*. .. seealso:: `hashing` init (bool): Include this attribute in the generated ``__init__`` method. It is possible to set this to False and set a default value. In that case this attributed is unconditionally initialized with the specified default value or factory. .. seealso:: `init` converter (typing.Callable | Converter): A callable that is called by *attrs*-generated ``__init__`` methods to convert attribute's value to the desired format. If a vanilla callable is passed, it is given the passed-in value as the only positional argument. It is possible to receive additional arguments by wrapping the callable in a `Converter`. Either way, the returned value will be used as the new value of the attribute. The value is converted before being passed to the validator, if any. .. seealso:: :ref:`converters` metadata (dict | None): An arbitrary mapping, to be used by third-party code. .. seealso:: `extending-metadata`. type (type): The type of the attribute. Nowadays, the preferred method to specify the type is using a variable annotation (see :pep:`526`). This argument is provided for backwards-compatibility and for usage with `make_class`. Regardless of the approach used, the type will be stored on ``Attribute.type``. Please note that *attrs* doesn't do anything with this metadata by itself. You can use it as part of your own code or for `static type checking `. kw_only (bool): Make this attribute keyword-only in the generated ``__init__`` (if ``init`` is False, this parameter is ignored). on_setattr (~typing.Callable | list[~typing.Callable] | None | ~typing.Literal[attrs.setters.NO_OP]): Allows to overwrite the *on_setattr* setting from `attr.s`. If left None, the *on_setattr* value from `attr.s` is used. Set to `attrs.setters.NO_OP` to run **no** `setattr` hooks for this attribute -- regardless of the setting in `define()`. alias (str | None): Override this attribute's parameter name in the generated ``__init__`` method. If left None, default to ``name`` stripped of leading underscores. See `private-attributes`. .. versionadded:: 20.1.0 .. versionchanged:: 21.1.0 *eq*, *order*, and *cmp* also accept a custom callable .. versionadded:: 22.2.0 *alias* .. versionadded:: 23.1.0 The *type* parameter has been re-added; mostly for `attrs.make_class`. Please note that type checkers ignore this metadata. .. seealso:: `attr.ib` """ return attrib( default=default, validator=validator, repr=repr, hash=hash, init=init, metadata=metadata, type=type, converter=converter, factory=factory, kw_only=kw_only, eq=eq, order=order, on_setattr=on_setattr, alias=alias, ) def asdict(inst, *, recurse=True, filter=None, value_serializer=None): """ Same as `attr.asdict`, except that collections types are always retained and dict is always used as *dict_factory*. .. versionadded:: 21.3.0 """ return _asdict( inst=inst, recurse=recurse, filter=filter, value_serializer=value_serializer, retain_collection_types=True, ) def astuple(inst, *, recurse=True, filter=None): """ Same as `attr.astuple`, except that collections types are always retained and `tuple` is always used as the *tuple_factory*. .. versionadded:: 21.3.0 """ return _astuple( inst=inst, recurse=recurse, filter=filter, retain_collection_types=True )