# SPDX-License-Identifier: MIT
import copy
from ._compat import PY_3_9_PLUS, get_generic_base
from ._make import NOTHING, _obj_setattr, fields
from .exceptions import AttrsAttributeNotFoundError
def asdict(
inst,
recurse=True,
filter=None,
dict_factory=dict,
retain_collection_types=False,
value_serializer=None,
):
"""
Return the *attrs* attribute values of *inst* as a dict.
Optionally recurse into other *attrs*-decorated classes.
:param inst: Instance of an *attrs*-decorated class.
:param bool recurse: Recurse into classes that are also
*attrs*-decorated.
:param callable filter: A callable whose return code determines whether an
attribute or element is included (``True``) or dropped (``False``). Is
called with the `attrs.Attribute` as the first argument and the
value as the second argument.
:param callable dict_factory: A callable to produce dictionaries from. For
example, to produce ordered dictionaries instead of normal Python
dictionaries, pass in ``collections.OrderedDict``.
:param bool retain_collection_types: Do not convert to ``list`` when
encountering an attribute whose type is ``tuple`` or ``set``. Only
meaningful if ``recurse`` is ``True``.
:param Optional[callable] value_serializer: A hook that is called for every
attribute or dict key/value. It receives the current instance, field
and value and must return the (updated) value. The hook is run *after*
the optional *filter* has been applied.
:rtype: return type of *dict_factory*
:raise attrs.exceptions.NotAnAttrsClassError: If *cls* is not an *attrs*
class.
.. versionadded:: 16.0.0 *dict_factory*
.. versionadded:: 16.1.0 *retain_collection_types*
.. versionadded:: 20.3.0 *value_serializer*
.. versionadded:: 21.3.0 If a dict has a collection for a key, it is
serialized as a tuple.
"""
attrs = fields(inst.__class__)
rv = dict_factory()
for a in attrs:
v = getattr(inst, a.name)
if filter is not None and not filter(a, v):
continue
if value_serializer is not None:
v = value_serializer(inst, a, v)
if recurse is True:
if has(v.__class__):
rv[a.name] = asdict(
v,
recurse=True,
filter=filter,
dict_factory=dict_factory,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
)
elif isinstance(v, (tuple, list, set, frozenset)):
cf = v.__class__ if retain_collection_types is True else list
items = [
_asdict_anything(
i,
is_key=False,
filter=filter,
dict_factory=dict_factory,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
)
for i in v
]
try:
rv[a.name] = cf(items)
except TypeError:
if not issubclass(cf, tuple):
raise
# Workaround for TypeError: cf.__new__() missing 1 required
# positional argument (which appears, for a namedturle)
rv[a.name] = cf(*items)
elif isinstance(v, dict):
df = dict_factory
rv[a.name] = df(
(
_asdict_anything(
kk,
is_key=True,
filter=filter,
dict_factory=df,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
),
_asdict_anything(
vv,
is_key=False,
filter=filter,
dict_factory=df,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
),
)
for kk, vv in v.items()
)
else:
rv[a.name] = v
else:
rv[a.name] = v
return rv
def _asdict_anything(
val,
is_key,
filter,
dict_factory,
retain_collection_types,
value_serializer,
):
"""
``asdict`` only works on attrs instances, this works on anything.
"""
if getattr(val.__class__, "__attrs_attrs__", None) is not None:
# Attrs class.
rv = asdict(
val,
recurse=True,
filter=filter,
dict_factory=dict_factory,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
)
elif isinstance(val, (tuple, list, set, frozenset)):
if retain_collection_types is True:
cf = val.__class__
elif is_key:
cf = tuple
else:
cf = list
rv = cf(
[
_asdict_anything(
i,
is_key=False,
filter=filter,
dict_factory=dict_factory,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
)
for i in val
]
)
elif isinstance(val, dict):
df = dict_factory
rv = df(
(
_asdict_anything(
kk,
is_key=True,
filter=filter,
dict_factory=df,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
),
_asdict_anything(
vv,
is_key=False,
filter=filter,
dict_factory=df,
retain_collection_types=retain_collection_types,
value_serializer=value_serializer,
),
)
for kk, vv in val.items()
)
else:
rv = val
if value_serializer is not None:
rv = value_serializer(None, None, rv)
return rv
def astuple(
inst,
recurse=True,
filter=None,
tuple_factory=tuple,
retain_collection_types=False,
):
"""
Return the *attrs* attribute values of *inst* as a tuple.
Optionally recurse into other *attrs*-decorated classes.
:param inst: Instance of an *attrs*-decorated class.
:param bool recurse: Recurse into classes that are also
*attrs*-decorated.
:param callable filter: A callable whose return code determines whether an
attribute or element is included (``True``) or dropped (``False``). Is
called with the `attrs.Attribute` as the first argument and the
value as the second argument.
:param callable tuple_factory: A callable to produce tuples from. For
example, to produce lists instead of tuples.
:param bool retain_collection_types: Do not convert to ``list``
or ``dict`` when encountering an attribute which type is
``tuple``, ``dict`` or ``set``. Only meaningful if ``recurse`` is
``True``.
:rtype: return type of *tuple_factory*
:raise attrs.exceptions.NotAnAttrsClassError: If *cls* is not an *attrs*
class.
.. versionadded:: 16.2.0
"""
attrs = fields(inst.__class__)
rv = []
retain = retain_collection_types # Very long. :/
for a in attrs:
v = getattr(inst, a.name)
if filter is not None and not filter(a, v):
continue
if recurse is True:
if has(v.__class__):
rv.append(
astuple(
v,
recurse=True,
filter=filter,
tuple_factory=tuple_factory,
retain_collection_types=retain,
)
)
elif isinstance(v, (tuple, list, set, frozenset)):
cf = v.__class__ if retain is True else list
items = [
astuple(
j,
recurse=True,
filter=filter,
tuple_factory=tuple_factory,
retain_collection_types=retain,
)
if has(j.__class__)
else j
for j in v
]
try:
rv.append(cf(items))
except TypeError:
if not issubclass(cf, tuple):
raise
# Workaround for TypeError: cf.__new__() missing 1 required
# positional argument (which appears, for a namedturle)
rv.append(cf(*items))
elif isinstance(v, dict):
df = v.__class__ if retain is True else dict
rv.append(
df(
(
astuple(
kk,
tuple_factory=tuple_factory,
retain_collection_types=retain,
)
if has(kk.__class__)
else kk,
astuple(
vv,
tuple_factory=tuple_factory,
retain_collection_types=retain,
)
if has(vv.__class__)
else vv,
)
for kk, vv in v.items()
)
)
else:
rv.append(v)
else:
rv.append(v)
return rv if tuple_factory is list else tuple_factory(rv)
[docs]
def has(cls):
"""
Check whether *cls* is a class with *attrs* attributes.
:param type cls: Class to introspect.
:raise TypeError: If *cls* is not a class.
:rtype: bool
"""
attrs = getattr(cls, "__attrs_attrs__", None)
if attrs is not None:
return True
# No attrs, maybe it's a specialized generic (A[str])?
generic_base = get_generic_base(cls)
if generic_base is not None:
generic_attrs = getattr(generic_base, "__attrs_attrs__", None)
if generic_attrs is not None:
# Stick it on here for speed next time.
cls.__attrs_attrs__ = generic_attrs
return generic_attrs is not None
return False
[docs]
def assoc(inst, **changes):
"""
Copy *inst* and apply *changes*.
This is different from `evolve` that applies the changes to the arguments
that create the new instance.
`evolve`'s behavior is preferable, but there are `edge cases`_ where it
doesn't work. Therefore `assoc` is deprecated, but will not be removed.
.. _`edge cases`: https://github.com/python-attrs/attrs/issues/251
:param inst: Instance of a class with *attrs* attributes.
:param changes: Keyword changes in the new copy.
:return: A copy of inst with *changes* incorporated.
:raise attrs.exceptions.AttrsAttributeNotFoundError: If *attr_name*
couldn't be found on *cls*.
:raise attrs.exceptions.NotAnAttrsClassError: If *cls* is not an *attrs*
class.
.. deprecated:: 17.1.0
Use `attrs.evolve` instead if you can.
This function will not be removed du to the slightly different approach
compared to `attrs.evolve`.
"""
new = copy.copy(inst)
attrs = fields(inst.__class__)
for k, v in changes.items():
a = getattr(attrs, k, NOTHING)
if a is NOTHING:
msg = f"{k} is not an attrs attribute on {new.__class__}."
raise AttrsAttributeNotFoundError(msg)
_obj_setattr(new, k, v)
return new
[docs]
def evolve(*args, **changes):
"""
Create a new instance, based on the first positional argument with
*changes* applied.
:param inst: Instance of a class with *attrs* attributes.
:param changes: Keyword changes in the new copy.
:return: A copy of inst with *changes* incorporated.
:raise TypeError: If *attr_name* couldn't be found in the class
``__init__``.
:raise attrs.exceptions.NotAnAttrsClassError: If *cls* is not an *attrs*
class.
.. versionadded:: 17.1.0
.. deprecated:: 23.1.0
It is now deprecated to pass the instance using the keyword argument
*inst*. It will raise a warning until at least April 2024, after which
it will become an error. Always pass the instance as a positional
argument.
"""
# Try to get instance by positional argument first.
# Use changes otherwise and warn it'll break.
if args:
try:
(inst,) = args
except ValueError:
msg = f"evolve() takes 1 positional argument, but {len(args)} were given"
raise TypeError(msg) from None
else:
try:
inst = changes.pop("inst")
except KeyError:
msg = "evolve() missing 1 required positional argument: 'inst'"
raise TypeError(msg) from None
import warnings
warnings.warn(
"Passing the instance per keyword argument is deprecated and "
"will stop working in, or after, April 2024.",
DeprecationWarning,
stacklevel=2,
)
cls = inst.__class__
attrs = fields(cls)
for a in attrs:
if not a.init:
continue
attr_name = a.name # To deal with private attributes.
init_name = a.alias
if init_name not in changes:
changes[init_name] = getattr(inst, attr_name)
return cls(**changes)
[docs]
def resolve_types(
cls, globalns=None, localns=None, attribs=None, include_extras=True
):
"""
Resolve any strings and forward annotations in type annotations.
This is only required if you need concrete types in `Attribute`'s *type*
field. In other words, you don't need to resolve your types if you only
use them for static type checking.
With no arguments, names will be looked up in the module in which the class
was created. If this is not what you want, e.g. if the name only exists
inside a method, you may pass *globalns* or *localns* to specify other
dictionaries in which to look up these names. See the docs of
`typing.get_type_hints` for more details.
:param type cls: Class to resolve.
:param Optional[dict] globalns: Dictionary containing global variables.
:param Optional[dict] localns: Dictionary containing local variables.
:param Optional[list] attribs: List of attribs for the given class.
This is necessary when calling from inside a ``field_transformer``
since *cls* is not an *attrs* class yet.
:param bool include_extras: Resolve more accurately, if possible.
Pass ``include_extras`` to ``typing.get_hints``, if supported by the
typing module. On supported Python versions (3.9+), this resolves the
types more accurately.
:raise TypeError: If *cls* is not a class.
:raise attrs.exceptions.NotAnAttrsClassError: If *cls* is not an *attrs*
class and you didn't pass any attribs.
:raise NameError: If types cannot be resolved because of missing variables.
:returns: *cls* so you can use this function also as a class decorator.
Please note that you have to apply it **after** `attrs.define`. That
means the decorator has to come in the line **before** `attrs.define`.
.. versionadded:: 20.1.0
.. versionadded:: 21.1.0 *attribs*
.. versionadded:: 23.1.0 *include_extras*
"""
# Since calling get_type_hints is expensive we cache whether we've
# done it already.
if getattr(cls, "__attrs_types_resolved__", None) != cls:
import typing
kwargs = {"globalns": globalns, "localns": localns}
if PY_3_9_PLUS:
kwargs["include_extras"] = include_extras
hints = typing.get_type_hints(cls, **kwargs)
for field in fields(cls) if attribs is None else attribs:
if field.name in hints:
# Since fields have been frozen we must work around it.
_obj_setattr(field, "type", hints[field.name])
# We store the class we resolved so that subclasses know they haven't
# been resolved.
cls.__attrs_types_resolved__ = cls
# Return the class so you can use it as a decorator too.
return cls
