blob: 2877f8e101ef9c79e3afcb4a166632b9ff9b78f3 [file] [log] [blame]
from __future__ import absolute_import, division, print_function
import hashlib
import linecache
import sys
from operator import itemgetter
from . import _config
from ._compat import (
PY2,
iteritems,
isclass,
metadata_proxy,
set_closure_cell,
)
from .exceptions import (
DefaultAlreadySetError,
FrozenInstanceError,
NotAnAttrsClassError,
UnannotatedAttributeError,
)
# This is used at least twice, so cache it here.
_obj_setattr = object.__setattr__
_init_convert_pat = "__attr_convert_{}"
_init_factory_pat = "__attr_factory_{}"
_tuple_property_pat = " {attr_name} = property(itemgetter({index}))"
_empty_metadata_singleton = metadata_proxy({})
class _Nothing(object):
"""
Sentinel class to indicate the lack of a value when ``None`` is ambiguous.
All instances of `_Nothing` are equal.
"""
def __copy__(self):
return self
def __deepcopy__(self, _):
return self
def __eq__(self, other):
return other.__class__ == _Nothing
def __ne__(self, other):
return not self == other
def __repr__(self):
return "NOTHING"
def __hash__(self):
return 0xdeadbeef
NOTHING = _Nothing()
"""
Sentinel to indicate the lack of a value when ``None`` is ambiguous.
"""
def attrib(default=NOTHING, validator=None,
repr=True, cmp=True, hash=None, init=True,
convert=None, metadata={}, type=None):
"""
Create a new attribute on a class.
.. warning::
Does *not* do anything unless the class is also decorated with
:func:`attr.s`!
:param 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 :class:`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 ``attr.NOTHING``), a value
*must* be supplied when instantiating; otherwise a :exc:`TypeError`
will be raised.
The default can also be set using decorator notation as shown below.
:type default: Any value.
:param validator: :func:`callable` that is called by ``attrs``-generated
``__init__`` methods after the instance has been initialized. They
receive the initialized instance, the :class:`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
:func:`get_run_validators`.
The validator can also be set using decorator notation as shown below.
:type validator: ``callable`` or a ``list`` of ``callable``\ s.
:param bool repr: Include this attribute in the generated ``__repr__``
method.
:param bool cmp: Include this attribute in the generated comparison methods
(``__eq__`` et al).
:param hash: Include this attribute in the generated ``__hash__``
method. If ``None`` (default), mirror *cmp*'s value. This is the
correct behavior according the Python spec. Setting this value to
anything else than ``None`` is *discouraged*.
:type hash: ``bool`` or ``None``
:param bool init: 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.
:param callable convert: :func:`callable` that is called by
``attrs``-generated ``__init__`` methods to convert attribute's value
to the desired format. It is given the passed-in value, and 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.
:param metadata: An arbitrary mapping, to be used by third-party
components. See :ref:`extending_metadata`.
:param type: The type of the attribute. In Python 3.6 or greater, the
preferred method to specify the type is using a variable annotation
(see `PEP 526 <https://www.python.org/dev/peps/pep-0526/>`_).
This argument is provided for backward compatibility.
Regardless of the approach used, the type will be stored on
``Attribute.type``.
.. versionchanged:: 17.1.0 *validator* can be a ``list`` now.
.. versionchanged:: 17.1.0
*hash* is ``None`` and therefore mirrors *cmp* by default.
.. versionadded:: 17.3.0 *type*
"""
if hash is not None and hash is not True and hash is not False:
raise TypeError(
"Invalid value for hash. Must be True, False, or None."
)
return _CountingAttr(
default=default,
validator=validator,
repr=repr,
cmp=cmp,
hash=hash,
init=init,
convert=convert,
metadata=metadata,
type=type,
)
def _make_attr_tuple_class(cls_name, attr_names):
"""
Create a tuple subclass to hold `Attribute`s for an `attrs` class.
The subclass is a bare tuple with properties for names.
class MyClassAttributes(tuple):
__slots__ = ()
x = property(itemgetter(0))
"""
attr_class_name = "{}Attributes".format(cls_name)
attr_class_template = [
"class {}(tuple):".format(attr_class_name),
" __slots__ = ()",
]
if attr_names:
for i, attr_name in enumerate(attr_names):
attr_class_template.append(_tuple_property_pat.format(
index=i,
attr_name=attr_name,
))
else:
attr_class_template.append(" pass")
globs = {"itemgetter": itemgetter}
eval(compile("\n".join(attr_class_template), "", "exec"), globs)
return globs[attr_class_name]
# Tuple class for extracted attributes from a class definition.
# `super_attrs` is a subset of `attrs`.
_Attributes = _make_attr_tuple_class("_Attributes", [
"attrs", # all attributes to build dunder methods for
"super_attrs", # attributes that have been inherited from super classes
])
def _is_class_var(annot):
"""
Check whether *annot* is a typing.ClassVar.
The implementation is gross but importing `typing` is slow and there are
discussions to remove it from the stdlib alltogether.
"""
return str(annot).startswith("typing.ClassVar")
def _transform_attrs(cls, these, auto_attribs):
"""
Transform all `_CountingAttr`s on a class into `Attribute`s.
If *these* is passed, use that and don't look for them on the class.
Return an `_Attributes`.
"""
cd = cls.__dict__
anns = getattr(cls, "__annotations__", {})
if these is None and auto_attribs is False:
ca_list = sorted((
(name, attr)
for name, attr
in cd.items()
if isinstance(attr, _CountingAttr)
), key=lambda e: e[1].counter)
elif these is None and auto_attribs is True:
ca_names = {
name
for name, attr
in cd.items()
if isinstance(attr, _CountingAttr)
}
ca_list = []
annot_names = set()
for attr_name, type in anns.items():
if _is_class_var(type):
continue
annot_names.add(attr_name)
a = cd.get(attr_name, NOTHING)
if not isinstance(a, _CountingAttr):
if a is NOTHING:
a = attrib()
else:
a = attrib(default=a)
ca_list.append((attr_name, a))
unannotated = ca_names - annot_names
if len(unannotated) > 0:
raise UnannotatedAttributeError(
"The following `attr.ib`s lack a type annotation: " +
", ".join(sorted(
unannotated,
key=lambda n: cd.get(n).counter
)) + "."
)
else:
ca_list = sorted((
(name, ca)
for name, ca
in iteritems(these)
), key=lambda e: e[1].counter)
non_super_attrs = [
Attribute.from_counting_attr(
name=attr_name,
ca=ca,
type=anns.get(attr_name),
)
for attr_name, ca
in ca_list
]
# Walk *down* the MRO for attributes. While doing so, we collect the names
# of attributes we've seen in `take_attr_names` and ignore their
# redefinitions deeper in the hierarchy.
super_attrs = []
taken_attr_names = set(a.name for a in non_super_attrs)
for super_cls in cls.__mro__[1:-1]:
sub_attrs = getattr(super_cls, "__attrs_attrs__", None)
if sub_attrs is not None:
# We iterate over sub_attrs backwards so we can reverse the whole
# list in the end and get all attributes in the order they have
# been defined.
for a in reversed(sub_attrs):
if a.name not in taken_attr_names:
super_attrs.append(a)
taken_attr_names.add(a.name)
# Now reverse the list, such that the attributes are sorted by *descending*
# age. IOW: the oldest attribute definition is at the head of the list.
super_attrs.reverse()
attr_names = [a.name for a in super_attrs + non_super_attrs]
AttrsClass = _make_attr_tuple_class(cls.__name__, attr_names)
attrs = AttrsClass(
super_attrs + [
Attribute.from_counting_attr(
name=attr_name,
ca=ca,
type=anns.get(attr_name)
)
for attr_name, ca
in ca_list
]
)
had_default = False
for a in attrs:
if had_default is True and a.default is NOTHING and a.init is True:
raise ValueError(
"No mandatory attributes allowed after an attribute with a "
"default value or factory. Attribute in question: {a!r}"
.format(a=a)
)
elif had_default is False and \
a.default is not NOTHING and \
a.init is not False:
had_default = True
return _Attributes((attrs, super_attrs))
def _frozen_setattrs(self, name, value):
"""
Attached to frozen classes as __setattr__.
"""
raise FrozenInstanceError()
def _frozen_delattrs(self, name):
"""
Attached to frozen classes as __delattr__.
"""
raise FrozenInstanceError()
class _ClassBuilder(object):
"""
Iteratively build *one* class.
"""
__slots__ = (
"_cls", "_cls_dict", "_attrs", "_super_names", "_attr_names", "_slots",
"_frozen", "_has_post_init",
)
def __init__(self, cls, these, slots, frozen, auto_attribs):
attrs, super_attrs = _transform_attrs(cls, these, auto_attribs)
self._cls = cls
self._cls_dict = dict(cls.__dict__) if slots else {}
self._attrs = attrs
self._super_names = set(a.name for a in super_attrs)
self._attr_names = tuple(a.name for a in attrs)
self._slots = slots
self._frozen = frozen or _has_frozen_superclass(cls)
self._has_post_init = bool(getattr(cls, "__attrs_post_init__", False))
self._cls_dict["__attrs_attrs__"] = self._attrs
if frozen:
self._cls_dict["__setattr__"] = _frozen_setattrs
self._cls_dict["__delattr__"] = _frozen_delattrs
def __repr__(self):
return "<_ClassBuilder(cls={cls})>".format(cls=self._cls.__name__)
def build_class(self):
"""
Finalize class based on the accumulated configuration.
Builder cannot be used anymore after calling this method.
"""
if self._slots is True:
return self._create_slots_class()
else:
return self._patch_original_class()
def _patch_original_class(self):
"""
Apply accumulated methods and return the class.
"""
cls = self._cls
super_names = self._super_names
# Clean class of attribute definitions (`attr.ib()`s).
for name in self._attr_names:
if name not in super_names and \
getattr(cls, name, None) is not None:
delattr(cls, name)
# Attach our dunder methods.
for name, value in self._cls_dict.items():
setattr(cls, name, value)
return cls
def _create_slots_class(self):
"""
Build and return a new class with a `__slots__` attribute.
"""
super_names = self._super_names
cd = {
k: v
for k, v in iteritems(self._cls_dict)
if k not in tuple(self._attr_names) + ("__dict__",)
}
# We only add the names of attributes that aren't inherited.
# Settings __slots__ to inherited attributes wastes memory.
cd["__slots__"] = tuple(
name
for name in self._attr_names
if name not in super_names
)
qualname = getattr(self._cls, "__qualname__", None)
if qualname is not None:
cd["__qualname__"] = qualname
attr_names = tuple(self._attr_names)
def slots_getstate(self):
"""
Automatically created by attrs.
"""
return tuple(getattr(self, name) for name in attr_names)
def slots_setstate(self, state):
"""
Automatically created by attrs.
"""
__bound_setattr = _obj_setattr.__get__(self, Attribute)
for name, value in zip(attr_names, state):
__bound_setattr(name, value)
# slots and frozen require __getstate__/__setstate__ to work
cd["__getstate__"] = slots_getstate
cd["__setstate__"] = slots_setstate
# Create new class based on old class and our methods.
cls = type(self._cls)(
self._cls.__name__,
self._cls.__bases__,
cd,
)
# The following is a fix for
# https://github.com/python-attrs/attrs/issues/102. On Python 3,
# if a method mentions `__class__` or uses the no-arg super(), the
# compiler will bake a reference to the class in the method itself
# as `method.__closure__`. Since we replace the class with a
# clone, we rewrite these references so it keeps working.
for item in cls.__dict__.values():
if isinstance(item, (classmethod, staticmethod)):
# Class- and staticmethods hide their functions inside.
# These might need to be rewritten as well.
closure_cells = getattr(item.__func__, "__closure__", None)
else:
closure_cells = getattr(item, "__closure__", None)
if not closure_cells: # Catch None or the empty list.
continue
for cell in closure_cells:
if cell.cell_contents is self._cls:
set_closure_cell(cell, cls)
return cls
def add_repr(self, ns):
self._cls_dict["__repr__"] = _make_repr(self._attrs, ns=ns)
return self
def add_str(self):
repr_ = self._cls_dict.get("__repr__")
if repr_ is None:
raise ValueError(
"__str__ can only be generated if a __repr__ exists."
)
self._cls_dict["__str__"] = repr_
return self
def make_unhashable(self):
self._cls_dict["__hash__"] = None
return self
def add_hash(self):
self._cls_dict["__hash__"] = _make_hash(self._attrs)
return self
def add_init(self):
self._cls_dict["__init__"] = _make_init(
self._attrs,
self._has_post_init,
self._frozen,
)
return self
def add_cmp(self):
cd = self._cls_dict
cd["__eq__"], cd["__ne__"], cd["__lt__"], cd["__le__"], cd["__gt__"], \
cd["__ge__"] = _make_cmp(self._attrs)
return self
def attrs(maybe_cls=None, these=None, repr_ns=None,
repr=True, cmp=True, hash=None, init=True,
slots=False, frozen=False, str=False, auto_attribs=False):
r"""
A class decorator that adds `dunder
<https://wiki.python.org/moin/DunderAlias>`_\ -methods according to the
specified attributes using :func:`attr.ib` or the *these* argument.
:param these: A dictionary of name to :func:`attr.ib` mappings. This is
useful to avoid the definition of your attributes within the class body
because you can't (e.g. 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.
:type these: :class:`dict` of :class:`str` to :func:`attr.ib`
:param str repr_ns: When using nested classes, there's no way in Python 2
to automatically detect that. Therefore it's possible to set the
namespace explicitly for a more meaningful ``repr`` output.
:param bool repr: Create a ``__repr__`` method with a human readable
representation of ``attrs`` attributes..
:param bool str: Create a ``__str__`` method that is identical to
``__repr__``. This is usually not necessary except for
:class:`Exception`\ s.
:param bool cmp: Create ``__eq__``, ``__ne__``, ``__lt__``, ``__le__``,
``__gt__``, and ``__ge__`` methods that compare the class as if it were
a tuple of its ``attrs`` attributes. But the attributes are *only*
compared, if the type of both classes is *identical*!
:param hash: If ``None`` (default), the ``__hash__`` method is generated
according how *cmp* and *frozen* are set.
1. If *both* are True, ``attrs`` will generate a ``__hash__`` for you.
2. If *cmp* is True and *frozen* is False, ``__hash__`` will be set to
None, marking it unhashable (which it is).
3. If *cmp* is False, ``__hash__`` will be left untouched meaning the
``__hash__`` method of the superclass will be used (if superclass 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 (e.g. 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.
See the `Python documentation \
<https://docs.python.org/3/reference/datamodel.html#object.__hash__>`_
and the `GitHub issue that led to the default behavior \
<https://github.com/python-attrs/attrs/issues/136>`_ for more details.
:type hash: ``bool`` or ``None``
:param bool init: Create a ``__init__`` method that initializes the
``attrs`` attributes. Leading underscores are stripped for the
argument name. If a ``__attrs_post_init__`` method exists on the
class, it will be called after the class is fully initialized.
:param bool slots: Create a slots_-style class that's more
memory-efficient. See :ref:`slots` for further ramifications.
:param bool frozen: Make instances immutable after initialization. If
someone attempts to modify a frozen instance,
:exc:`attr.exceptions.FrozenInstanceError` is raised.
Please note:
1. This is achieved by installing a custom ``__setattr__`` method
on your class so you can't implement an own one.
2. True immutability is impossible in Python.
3. This *does* have a minor a runtime performance :ref:`impact
<how-frozen>` 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)``.
.. _slots: https://docs.python.org/3/reference/datamodel.html#slots
:param bool auto_attribs: If True, collect `PEP 526`_-annotated attributes
(Python 3.6 and later only) from the class body.
In this case, you **must** annotate every field. If ``attrs``
encounters a field that is set to an :func:`attr.ib` but lacks a type
annotation, an :exc:`attr.exceptions.UnannotatedAttributeError` is
raised. Use ``field_name: typing.Any = attr.ib(...)`` if you don't
want to set a type.
If you assign a value to those attributes (e.g. ``x: int = 42``), that
value becomes the default value like if it were passed using
``attr.ib(default=42)``. Passing an instance of :class:`Factory` also
works as expected.
Attributes annotated as :data:`typing.ClassVar` are **ignored**.
.. _`PEP 526`: https://www.python.org/dev/peps/pep-0526/
.. versionadded:: 16.0.0 *slots*
.. versionadded:: 16.1.0 *frozen*
.. versionadded:: 16.3.0 *str*, and support for ``__attrs_post_init__``.
.. versionchanged::
17.1.0 *hash* supports ``None`` as value which is also the default
now.
.. versionadded:: 17.3.0 *auto_attribs*
"""
def wrap(cls):
if getattr(cls, "__class__", None) is None:
raise TypeError("attrs only works with new-style classes.")
builder = _ClassBuilder(cls, these, slots, frozen, auto_attribs)
if repr is True:
builder.add_repr(repr_ns)
if str is True:
builder.add_str()
if cmp is True:
builder.add_cmp()
if hash is not True and hash is not False and hash is not None:
# Can't use `hash in` because 1 == True for example.
raise TypeError(
"Invalid value for hash. Must be True, False, or None."
)
elif hash is False or (hash is None and cmp is False):
pass
elif hash is True or (hash is None and cmp is True and frozen is True):
builder.add_hash()
else:
builder.make_unhashable()
if init is True:
builder.add_init()
return builder.build_class()
# 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
else:
return wrap(maybe_cls)
_attrs = attrs
"""
Internal alias so we can use it in functions that take an argument called
*attrs*.
"""
if PY2:
def _has_frozen_superclass(cls):
"""
Check whether *cls* has a frozen ancestor by looking at its
__setattr__.
"""
return (
getattr(
cls.__setattr__, "__module__", None
) == _frozen_setattrs.__module__ and
cls.__setattr__.__name__ == _frozen_setattrs.__name__
)
else:
def _has_frozen_superclass(cls):
"""
Check whether *cls* has a frozen ancestor by looking at its
__setattr__.
"""
return cls.__setattr__ == _frozen_setattrs
def _attrs_to_tuple(obj, attrs):
"""
Create a tuple of all values of *obj*'s *attrs*.
"""
return tuple(getattr(obj, a.name) for a in attrs)
def _make_hash(attrs):
attrs = tuple(
a
for a in attrs
if a.hash is True or (a.hash is None and a.cmp is True)
)
def hash_(self):
"""
Automatically created by attrs.
"""
return hash(_attrs_to_tuple(self, attrs))
return hash_
def _add_hash(cls, attrs):
"""
Add a hash method to *cls*.
"""
cls.__hash__ = _make_hash(attrs)
return cls
def _make_cmp(attrs):
attrs = [a for a in attrs if a.cmp]
def attrs_to_tuple(obj):
"""
Save us some typing.
"""
return _attrs_to_tuple(obj, attrs)
def eq(self, other):
"""
Automatically created by attrs.
"""
if other.__class__ is self.__class__:
return attrs_to_tuple(self) == attrs_to_tuple(other)
else:
return NotImplemented
def ne(self, other):
"""
Automatically created by attrs.
"""
result = eq(self, other)
if result is NotImplemented:
return NotImplemented
else:
return not result
def lt(self, other):
"""
Automatically created by attrs.
"""
if isinstance(other, self.__class__):
return attrs_to_tuple(self) < attrs_to_tuple(other)
else:
return NotImplemented
def le(self, other):
"""
Automatically created by attrs.
"""
if isinstance(other, self.__class__):
return attrs_to_tuple(self) <= attrs_to_tuple(other)
else:
return NotImplemented
def gt(self, other):
"""
Automatically created by attrs.
"""
if isinstance(other, self.__class__):
return attrs_to_tuple(self) > attrs_to_tuple(other)
else:
return NotImplemented
def ge(self, other):
"""
Automatically created by attrs.
"""
if isinstance(other, self.__class__):
return attrs_to_tuple(self) >= attrs_to_tuple(other)
else:
return NotImplemented
return eq, ne, lt, le, gt, ge
def _add_cmp(cls, attrs=None):
"""
Add comparison methods to *cls*.
"""
if attrs is None:
attrs = cls.__attrs_attrs__
cls.__eq__, cls.__ne__, cls.__lt__, cls.__le__, cls.__gt__, cls.__ge__ = \
_make_cmp(attrs)
return cls
def _make_repr(attrs, ns):
"""
Make a repr method for *attr_names* adding *ns* to the full name.
"""
attr_names = tuple(
a.name
for a in attrs
if a.repr
)
def repr_(self):
"""
Automatically created by attrs.
"""
real_cls = self.__class__
if ns is None:
qualname = getattr(real_cls, "__qualname__", None)
if qualname is not None:
class_name = qualname.rsplit(">.", 1)[-1]
else:
class_name = real_cls.__name__
else:
class_name = ns + "." + real_cls.__name__
return "{0}({1})".format(
class_name,
", ".join(
name + "=" + repr(getattr(self, name))
for name in attr_names
)
)
return repr_
def _add_repr(cls, ns=None, attrs=None):
"""
Add a repr method to *cls*.
"""
if attrs is None:
attrs = cls.__attrs_attrs__
repr_ = _make_repr(attrs, ns)
cls.__repr__ = repr_
return cls
def _make_init(attrs, post_init, frozen):
attrs = [
a
for a in attrs
if a.init or a.default is not NOTHING
]
# We cache the generated init methods for the same kinds of attributes.
sha1 = hashlib.sha1()
sha1.update(repr(attrs).encode("utf-8"))
unique_filename = "<attrs generated init {0}>".format(
sha1.hexdigest()
)
script, globs = _attrs_to_script(
attrs,
frozen,
post_init,
)
locs = {}
bytecode = compile(script, unique_filename, "exec")
attr_dict = dict((a.name, a) for a in attrs)
globs.update({
"NOTHING": NOTHING,
"attr_dict": attr_dict,
})
if frozen is True:
# Save the lookup overhead in __init__ if we need to circumvent
# immutability.
globs["_cached_setattr"] = _obj_setattr
eval(bytecode, globs, locs)
init = locs["__init__"]
# In order of debuggers like PDB being able to step through the code,
# we add a fake linecache entry.
linecache.cache[unique_filename] = (
len(script),
None,
script.splitlines(True),
unique_filename
)
return init
def _add_init(cls, frozen):
"""
Add a __init__ method to *cls*. If *frozen* is True, make it immutable.
"""
cls.__init__ = _make_init(
cls.__attrs_attrs__,
getattr(cls, "__attrs_post_init__", False),
frozen,
)
return cls
def fields(cls):
"""
Returns the tuple of ``attrs`` attributes for a class.
The tuple also allows accessing the fields by their names (see below for
examples).
:param type cls: Class to introspect.
:raise TypeError: If *cls* is not a class.
:raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
class.
:rtype: tuple (with name accessors) of :class:`attr.Attribute`
.. versionchanged:: 16.2.0 Returned tuple allows accessing the fields
by name.
"""
if not isclass(cls):
raise TypeError("Passed object must be a class.")
attrs = getattr(cls, "__attrs_attrs__", None)
if attrs is None:
raise NotAnAttrsClassError(
"{cls!r} is not an attrs-decorated class.".format(cls=cls)
)
return attrs
def validate(inst):
"""
Validate all attributes on *inst* that have a validator.
Leaves all exceptions through.
:param inst: Instance of a class with ``attrs`` attributes.
"""
if _config._run_validators is False:
return
for a in fields(inst.__class__):
v = a.validator
if v is not None:
v(inst, a, getattr(inst, a.name))
def _attrs_to_script(attrs, frozen, post_init):
"""
Return a script of an initializer for *attrs* and a dict of globals.
The globals are expected by the generated script.
If *frozen* is True, we cannot set the attributes directly so we use
a cached ``object.__setattr__``.
"""
lines = []
if frozen is True:
lines.append(
# Circumvent the __setattr__ descriptor to save one lookup per
# assignment.
"_setattr = _cached_setattr.__get__(self, self.__class__)"
)
def fmt_setter(attr_name, value_var):
return "_setattr('%(attr_name)s', %(value_var)s)" % {
"attr_name": attr_name,
"value_var": value_var,
}
def fmt_setter_with_converter(attr_name, value_var):
conv_name = _init_convert_pat.format(attr_name)
return "_setattr('%(attr_name)s', %(conv)s(%(value_var)s))" % {
"attr_name": attr_name,
"value_var": value_var,
"conv": conv_name,
}
else:
def fmt_setter(attr_name, value):
return "self.%(attr_name)s = %(value)s" % {
"attr_name": attr_name,
"value": value,
}
def fmt_setter_with_converter(attr_name, value_var):
conv_name = _init_convert_pat.format(attr_name)
return "self.%(attr_name)s = %(conv)s(%(value_var)s)" % {
"attr_name": attr_name,
"value_var": value_var,
"conv": conv_name,
}
args = []
attrs_to_validate = []
# This is a dictionary of names to validator and converter callables.
# Injecting this into __init__ globals lets us avoid lookups.
names_for_globals = {}
for a in attrs:
if a.validator:
attrs_to_validate.append(a)
attr_name = a.name
arg_name = a.name.lstrip("_")
has_factory = isinstance(a.default, Factory)
if has_factory and a.default.takes_self:
maybe_self = "self"
else:
maybe_self = ""
if a.init is False:
if has_factory:
init_factory_name = _init_factory_pat.format(a.name)
if a.convert is not None:
lines.append(fmt_setter_with_converter(
attr_name,
init_factory_name + "({0})".format(maybe_self)))
conv_name = _init_convert_pat.format(a.name)
names_for_globals[conv_name] = a.convert
else:
lines.append(fmt_setter(
attr_name,
init_factory_name + "({0})".format(maybe_self)
))
names_for_globals[init_factory_name] = a.default.factory
else:
if a.convert is not None:
lines.append(fmt_setter_with_converter(
attr_name,
"attr_dict['{attr_name}'].default"
.format(attr_name=attr_name)
))
conv_name = _init_convert_pat.format(a.name)
names_for_globals[conv_name] = a.convert
else:
lines.append(fmt_setter(
attr_name,
"attr_dict['{attr_name}'].default"
.format(attr_name=attr_name)
))
elif a.default is not NOTHING and not has_factory:
args.append(
"{arg_name}=attr_dict['{attr_name}'].default".format(
arg_name=arg_name,
attr_name=attr_name,
)
)
if a.convert is not None:
lines.append(fmt_setter_with_converter(attr_name, arg_name))
names_for_globals[_init_convert_pat.format(a.name)] = a.convert
else:
lines.append(fmt_setter(attr_name, arg_name))
elif has_factory:
args.append("{arg_name}=NOTHING".format(arg_name=arg_name))
lines.append("if {arg_name} is not NOTHING:"
.format(arg_name=arg_name))
init_factory_name = _init_factory_pat.format(a.name)
if a.convert is not None:
lines.append(" " + fmt_setter_with_converter(attr_name,
arg_name))
lines.append("else:")
lines.append(" " + fmt_setter_with_converter(
attr_name,
init_factory_name + "({0})".format(maybe_self)
))
names_for_globals[_init_convert_pat.format(a.name)] = a.convert
else:
lines.append(" " + fmt_setter(attr_name, arg_name))
lines.append("else:")
lines.append(" " + fmt_setter(
attr_name,
init_factory_name + "({0})".format(maybe_self)
))
names_for_globals[init_factory_name] = a.default.factory
else:
args.append(arg_name)
if a.convert is not None:
lines.append(fmt_setter_with_converter(attr_name, arg_name))
names_for_globals[_init_convert_pat.format(a.name)] = a.convert
else:
lines.append(fmt_setter(attr_name, arg_name))
if attrs_to_validate: # we can skip this if there are no validators.
names_for_globals["_config"] = _config
lines.append("if _config._run_validators is True:")
for a in attrs_to_validate:
val_name = "__attr_validator_{}".format(a.name)
attr_name = "__attr_{}".format(a.name)
lines.append(" {}(self, {}, self.{})".format(
val_name, attr_name, a.name))
names_for_globals[val_name] = a.validator
names_for_globals[attr_name] = a
if post_init:
lines.append("self.__attrs_post_init__()")
return """\
def __init__(self, {args}):
{lines}
""".format(
args=", ".join(args),
lines="\n ".join(lines) if lines else "pass",
), names_for_globals
class Attribute(object):
"""
*Read-only* representation of an attribute.
:attribute name: The name of the attribute.
Plus *all* arguments of :func:`attr.ib`.
"""
__slots__ = (
"name", "default", "validator", "repr", "cmp", "hash", "init",
"convert", "metadata", "type"
)
def __init__(self, name, default, validator, repr, cmp, hash, init,
convert=None, metadata=None, type=None):
# Cache this descriptor here to speed things up later.
bound_setattr = _obj_setattr.__get__(self, Attribute)
bound_setattr("name", name)
bound_setattr("default", default)
bound_setattr("validator", validator)
bound_setattr("repr", repr)
bound_setattr("cmp", cmp)
bound_setattr("hash", hash)
bound_setattr("init", init)
bound_setattr("convert", convert)
bound_setattr("metadata", (metadata_proxy(metadata) if metadata
else _empty_metadata_singleton))
bound_setattr("type", type)
def __setattr__(self, name, value):
raise FrozenInstanceError()
@classmethod
def from_counting_attr(cls, name, ca, type=None):
# type holds the annotated value. deal with conflicts:
if type is None:
type = ca.type
elif ca.type is not None:
raise ValueError(
"Type annotation and type argument cannot both be present"
)
inst_dict = {
k: getattr(ca, k)
for k
in Attribute.__slots__
if k not in (
"name", "validator", "default", "type"
) # exclude methods
}
return cls(name=name, validator=ca._validator, default=ca._default,
type=type, **inst_dict)
# Don't use _add_pickle since fields(Attribute) doesn't work
def __getstate__(self):
"""
Play nice with pickle.
"""
return tuple(getattr(self, name) if name != "metadata"
else dict(self.metadata)
for name in self.__slots__)
def __setstate__(self, state):
"""
Play nice with pickle.
"""
bound_setattr = _obj_setattr.__get__(self, Attribute)
for name, value in zip(self.__slots__, state):
if name != "metadata":
bound_setattr(name, value)
else:
bound_setattr(name, metadata_proxy(value) if value else
_empty_metadata_singleton)
_a = [Attribute(name=name, default=NOTHING, validator=None,
repr=True, cmp=True, hash=(name != "metadata"), init=True)
for name in Attribute.__slots__]
Attribute = _add_hash(
_add_cmp(_add_repr(Attribute, attrs=_a), attrs=_a),
attrs=[a for a in _a if a.hash]
)
class _CountingAttr(object):
"""
Intermediate representation of attributes that uses a counter to preserve
the order in which the attributes have been defined.
*Internal* data structure of the attrs library. Running into is most
likely the result of a bug like a forgotten `@attr.s` decorator.
"""
__slots__ = ("counter", "_default", "repr", "cmp", "hash", "init",
"metadata", "_validator", "convert", "type")
__attrs_attrs__ = tuple(
Attribute(name=name, default=NOTHING, validator=None,
repr=True, cmp=True, hash=True, init=True)
for name
in ("counter", "_default", "repr", "cmp", "hash", "init",)
) + (
Attribute(name="metadata", default=None, validator=None,
repr=True, cmp=True, hash=False, init=True),
)
cls_counter = 0
def __init__(self, default, validator, repr, cmp, hash, init, convert,
metadata, type):
_CountingAttr.cls_counter += 1
self.counter = _CountingAttr.cls_counter
self._default = default
# If validator is a list/tuple, wrap it using helper validator.
if validator and isinstance(validator, (list, tuple)):
self._validator = and_(*validator)
else:
self._validator = validator
self.repr = repr
self.cmp = cmp
self.hash = hash
self.init = init
self.convert = convert
self.metadata = metadata
self.type = type
def validator(self, meth):
"""
Decorator that adds *meth* to the list of validators.
Returns *meth* unchanged.
.. versionadded:: 17.1.0
"""
if self._validator is None:
self._validator = meth
else:
self._validator = and_(self._validator, meth)
return meth
def default(self, meth):
"""
Decorator that allows to set the default for an attribute.
Returns *meth* unchanged.
:raises DefaultAlreadySetError: If default has been set before.
.. versionadded:: 17.1.0
"""
if self._default is not NOTHING:
raise DefaultAlreadySetError()
self._default = Factory(meth, takes_self=True)
return meth
_CountingAttr = _add_cmp(_add_repr(_CountingAttr))
@attrs(slots=True, init=False, hash=True)
class Factory(object):
"""
Stores a factory callable.
If passed as the default value to :func:`attr.ib`, the factory is used to
generate a new value.
:param callable factory: A callable that takes either none or exactly one
mandatory positional argument depending on *takes_self*.
:param bool takes_self: Pass the partially initialized instance that is
being initialized as a positional argument.
.. versionadded:: 17.1.0 *takes_self*
"""
factory = attrib()
takes_self = attrib()
def __init__(self, factory, takes_self=False):
"""
`Factory` is part of the default machinery so if we want a default
value here, we have to implement it ourselves.
"""
self.factory = factory
self.takes_self = takes_self
def make_class(name, attrs, bases=(object,), **attributes_arguments):
"""
A quick way to create a new class called *name* with *attrs*.
:param name: The name for the new class.
:type name: str
:param attrs: A list of names or a dictionary of mappings of names to
attributes.
:type attrs: :class:`list` or :class:`dict`
:param tuple bases: Classes that the new class will subclass.
:param attributes_arguments: Passed unmodified to :func:`attr.s`.
:return: A new class with *attrs*.
:rtype: type
.. versionadded:: 17.1.0 *bases*
"""
if isinstance(attrs, dict):
cls_dict = attrs
elif isinstance(attrs, (list, tuple)):
cls_dict = dict((a, attrib()) for a in attrs)
else:
raise TypeError("attrs argument must be a dict or a list.")
post_init = cls_dict.pop("__attrs_post_init__", None)
type_ = type(
name,
bases,
{} if post_init is None else {"__attrs_post_init__": post_init}
)
# For pickling to work, the __module__ variable needs to be set to the
# frame where the class is created. Bypass this step in environments where
# sys._getframe is not defined (Jython for example) or sys._getframe is not
# defined for arguments greater than 0 (IronPython).
try:
type_.__module__ = sys._getframe(1).f_globals.get(
"__name__", "__main__",
)
except (AttributeError, ValueError):
pass
return _attrs(these=cls_dict, **attributes_arguments)(type_)
# These are required by within this module so we define them here and merely
# import into .validators.
@attrs(slots=True, hash=True)
class _AndValidator(object):
"""
Compose many validators to a single one.
"""
_validators = attrib()
def __call__(self, inst, attr, value):
for v in self._validators:
v(inst, attr, value)
def and_(*validators):
"""
A validator that composes multiple validators into one.
When called on a value, it runs all wrapped validators.
:param validators: Arbitrary number of validators.
:type validators: callables
.. versionadded:: 17.1.0
"""
vals = []
for validator in validators:
vals.extend(
validator._validators if isinstance(validator, _AndValidator)
else [validator]
)
return _AndValidator(tuple(vals))