# SPDX-License-Identifier: MIT
import copy
from ._compat import PY_3_9_PLUS, get_generic_base
from ._make import _OBJ_SETATTR, NOTHING, 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.
Args:
inst: Instance of an *attrs*-decorated class.
recurse (bool): Recurse into classes that are also *attrs*-decorated.
filter (~typing.Callable):
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.
dict_factory (~typing.Callable):
A callable to produce dictionaries from. For example, to produce
ordered dictionaries instead of normal Python dictionaries, pass in
``collections.OrderedDict``.
retain_collection_types (bool):
Do not convert to `list` when encountering an attribute whose type
is `tuple` or `set`. Only meaningful if *recurse* is `True`.
value_serializer (typing.Callable | None):
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.
Returns:
Return type of *dict_factory*.
Raises:
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.
Args:
inst: Instance of an *attrs*-decorated class.
recurse (bool):
Recurse into classes that are also *attrs*-decorated.
filter (~typing.Callable):
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.
tuple_factory (~typing.Callable):
A callable to produce tuples from. For example, to produce lists
instead of tuples.
retain_collection_types (bool):
Do not convert to `list` or `dict` when encountering an attribute
which type is `tuple`, `dict` or `set`. Only meaningful if
*recurse* is `True`.
Returns:
Return type of *tuple_factory*
Raises:
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.
Args:
cls (type): Class to introspect.
Raises:
TypeError: If *cls* is not a class.
Returns:
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
Args:
inst: Instance of a class with *attrs* attributes.
changes: Keyword changes in the new copy.
Returns:
A copy of inst with *changes* incorporated.
Raises:
attrs.exceptions.AttrsAttributeNotFoundError:
If *attr_name* couldn't be found on *cls*.
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`, though.
"""
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.
Args:
inst:
Instance of a class with *attrs* attributes. *inst* must be passed
as a positional argument.
changes:
Keyword changes in the new copy.
Returns:
A copy of inst with *changes* incorporated.
Raises:
TypeError:
If *attr_name* couldn't be found in the class ``__init__``.
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.
.. versionchanged:: 24.1.0
*inst* can't be passed as a keyword argument anymore.
"""
try:
(inst,) = args
except ValueError:
msg = (
f"evolve() takes 1 positional argument, but {len(args)} were given"
)
raise TypeError(msg) from None
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 :class:`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, for example, 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.
Args:
cls (type): Class to resolve.
globalns (dict | None): Dictionary containing global variables.
localns (dict | None): Dictionary containing local variables.
attribs (list | None):
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.
include_extras (bool):
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.
Raises:
TypeError: If *cls* is not a class.
attrs.exceptions.NotAnAttrsClassError:
If *cls* is not an *attrs* class and you didn't pass any attribs.
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
