from __future__ import absolute_import, division, print_function
import hashlib
import linecache
from . import _config
from ._compat import exec_, iteritems, isclass, iterkeys
from .exceptions import FrozenInstanceError
# This is used at least twice, so cache it here.
_obj_setattr = object.__setattr__
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 attr(default=NOTHING, validator=None,
repr=True, cmp=True, hash=True, init=True,
convert=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 datatypes 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.
:type default: Any value.
:param callable 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.
They can be globally disabled and re-enabled using
:func:`get_run_validators`.
: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 bool hash: Include this attribute in the generated ``__hash__``
method.
: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.
"""
return _CountingAttr(
default=default,
validator=validator,
repr=repr,
cmp=cmp,
hash=hash,
init=init,
convert=convert,
)
def _transform_attrs(cls, these):
"""
Transforms all `_CountingAttr`s on a class into `Attribute`s and saves the
list as a tuple in `__attrs_attrs__`.
If *these* is passed, use that and don't look for them on the class.
"""
super_cls = []
for c in reversed(cls.__mro__[1:-1]):
sub_attrs = getattr(c, "__attrs_attrs__", None)
if sub_attrs is not None:
super_cls.extend(a for a in sub_attrs if a not in super_cls)
if these is None:
ca_list = [(name, attr)
for name, attr
in cls.__dict__.items()
if isinstance(attr, _CountingAttr)]
else:
ca_list = [(name, ca)
for name, ca
in iteritems(these)]
cls.__attrs_attrs__ = tuple(super_cls + [
Attribute.from_counting_attr(name=attr_name, ca=ca)
for attr_name, ca
in sorted(ca_list, key=lambda e: e[1].counter)
])
had_default = False
for a in cls.__attrs_attrs__:
if these is None and a not in super_cls:
setattr(cls, a.name, a)
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
def _frozen_setattrs(self, name, value):
"""
Attached to frozen classes as __setattr__.
"""
raise FrozenInstanceError()
def attributes(maybe_cls=None, these=None, repr_ns=None,
repr=True, cmp=True, hash=True, init=True,
slots=False, frozen=False):
"""
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 (e.g. if you want to use
:class:`properties <property>`).
If *these* is not `None`, the class body is *ignored*.
: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
represantation of ``attrs`` attributes..
: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 bool hash: Create a ``__hash__`` method that returns the
:func:`hash` of a tuple of all ``attrs`` attribute values.
:param bool init: Create a ``__init__`` method that initialiazes the
``attrs`` attributes. Leading underscores are stripped for the
argument name.
: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``.
.. _slots: https://docs.python.org/3.5/reference/datamodel.html#slots
.. versionadded:: 16.0.0 *slots*
.. versionadded:: 16.1.0 *frozen*
"""
def wrap(cls):
if getattr(cls, "__class__", None) is None:
raise TypeError("attrs only works with new-style classes.")
if slots:
# Only need this later if we're using slots.
if these is None:
ca_list = [name
for name, attr
in cls.__dict__.items()
if isinstance(attr, _CountingAttr)]
else:
ca_list = list(iterkeys(these))
_transform_attrs(cls, these)
if repr is True:
cls = _add_repr(cls, ns=repr_ns)
if cmp is True:
cls = _add_cmp(cls)
if hash is True:
cls = _add_hash(cls)
if init is True:
cls = _add_init(cls, frozen)
if frozen is True:
cls.__setattr__ = _frozen_setattrs
if slots is True:
cls_dict = dict(cls.__dict__)
cls_dict["__slots__"] = tuple(ca_list)
for ca_name in ca_list:
# It might not actually be in there, e.g. if using 'these'.
cls_dict.pop(ca_name, None)
cls_dict.pop('__dict__', None)
if repr_ns is None:
cls_name = getattr(cls, "__qualname__", cls.__name__)
else:
cls_name = cls.__name__
cls = type(cls_name, cls.__bases__, cls_dict)
return cls
# attrs_or class type depends on the usage of the decorator. It's a class
# if it's used as `@attributes` but ``None`` if used # as `@attributes()`.
if maybe_cls is None:
return wrap
else:
return wrap(maybe_cls)
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 _add_hash(cls, attrs=None):
"""
Add a hash method to *cls*.
"""
if attrs is None:
attrs = [a for a in cls.__attrs_attrs__ if a.hash]
def hash_(self):
"""
Automatically created by attrs.
"""
return hash(_attrs_to_tuple(self, attrs))
cls.__hash__ = hash_
return cls
def _add_cmp(cls, attrs=None):
"""
Add comparison methods to *cls*.
"""
if attrs is None:
attrs = [a for a in cls.__attrs_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
cls.__eq__ = eq
cls.__ne__ = ne
cls.__lt__ = lt
cls.__le__ = le
cls.__gt__ = gt
cls.__ge__ = ge
return cls
def _add_repr(cls, ns=None, attrs=None):
"""
Add a repr method to *cls*.
"""
if attrs is None:
attrs = [a for a in cls.__attrs_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(a.name + "=" + repr(getattr(self, a.name))
for a in attrs)
)
cls.__repr__ = repr_
return cls
def _add_init(cls, frozen):
"""
Add a __init__ method to *cls*. If *frozen* is True, make it immutable.
"""
attrs = [a for a in cls.__attrs_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)
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,
"validate": validate,
"_convert": _convert
})
if frozen is True:
# Save the lookup overhead in __init__ if we need to circumvent
# immutability.
globs["_cached_setattr"] = _obj_setattr
exec_(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
)
cls.__init__ = init
return cls
def fields(cls):
"""
Returns the tuple of ``attrs`` attributes for a class.
:param type cls: Class to introspect.
:raise TypeError: If *cls* is not a class.
:raise ValueError: If *cls* is not an ``attrs`` class.
:rtype: tuple of :class:`attr.Attribute`
"""
if not isclass(cls):
raise TypeError("Passed object must be a class.")
attrs = getattr(cls, "__attrs_attrs__", None)
if attrs is None:
raise ValueError("{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__):
if a.validator is not None:
a.validator(inst, a, getattr(inst, a.name))
def _convert(inst):
"""
Convert all attributes on *inst* that have a converter.
Leaves all exceptions through.
:param inst: Instance of a class with ``attrs`` attributes.
"""
for a in inst.__class__.__attrs_attrs__:
if a.convert is not None:
setattr(inst, a.name, a.convert(getattr(inst, a.name)))
def _attrs_to_script(attrs, frozen):
"""
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):
return "_setattr('%(attr_name)s', %(value)s)" % {
"attr_name": attr_name,
"value": value,
}
else:
def fmt_setter(attr_name, value):
return "self.%(attr_name)s = %(value)s" % {
"attr_name": attr_name,
"value": value,
}
args = []
has_convert = False
attrs_to_validate = []
# This is a dictionary of names to validator callables. Injecting
# this into __init__ globals lets us avoid lookups.
validators_for_globals = {}
for a in attrs:
if a.validator is not None:
attrs_to_validate.append(a)
if a.convert is not None:
has_convert = True
attr_name = a.name
arg_name = a.name.lstrip("_")
if a.init is False:
if isinstance(a.default, Factory):
lines.append(fmt_setter(
attr_name,
"attr_dict['{attr_name}'].default.factory()"
.format(attr_name=attr_name)
))
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 isinstance(a.default, Factory):
args.append(
"{arg_name}=attr_dict['{attr_name}'].default".format(
arg_name=arg_name,
attr_name=attr_name,
)
)
lines.append(fmt_setter(attr_name, arg_name))
elif a.default is not NOTHING and isinstance(a.default, Factory):
args.append("{arg_name}=NOTHING".format(arg_name=arg_name))
lines.append("if {arg_name} is not NOTHING:"
.format(arg_name=arg_name))
lines.append(" " + fmt_setter(attr_name, arg_name))
lines.append("else:")
lines.append(" " + fmt_setter(
attr_name,
"attr_dict['{attr_name}'].default.factory()"
.format(attr_name=attr_name)
))
else:
args.append(arg_name)
lines.append(fmt_setter(attr_name, arg_name))
if has_convert:
lines.append("_convert(self)")
if attrs_to_validate: # we can skip this if there are no validators.
validators_for_globals["_config"] = _config
lines.append("if _config._run_validators is False:")
lines.append(" return")
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))
validators_for_globals[val_name] = a.validator
validators_for_globals[attr_name] = a
return """\
def __init__(self, {args}):
{lines}
""".format(
args=", ".join(args),
lines="\n ".join(lines) if lines else "pass",
), validators_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')
_optional = {"convert": None}
def __init__(self, name, default, validator, repr, cmp, hash, init,
convert=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)
def __setattr__(self, name, value):
raise FrozenInstanceError()
@classmethod
def from_counting_attr(cls, name, ca):
return cls(name=name,
**dict((k, getattr(ca, k))
for k
in Attribute.__slots__
if k != "name"))
_a = [Attribute(name=name, default=NOTHING, validator=None,
repr=True, cmp=True, hash=True, init=True)
for name in Attribute.__slots__]
Attribute = _add_hash(
_add_cmp(_add_repr(Attribute, attrs=_a), attrs=_a), attrs=_a
)
class _CountingAttr(object):
"""
Intermediate representation of attributes that uses a counter to preserve
the order in which the attributes have been defined.
"""
__attrs_attrs__ = [
Attribute(name=name, default=NOTHING, validator=None,
repr=True, cmp=True, hash=True, init=True)
for name
in ("counter", "default", "repr", "cmp", "hash", "init",)
]
counter = 0
def __init__(self, default, validator, repr, cmp, hash, init, convert):
_CountingAttr.counter += 1
self.counter = _CountingAttr.counter
self.default = default
self.validator = validator
self.repr = repr
self.cmp = cmp
self.hash = hash
self.init = init
self.convert = convert
_CountingAttr = _add_cmp(_add_repr(_CountingAttr))
@attributes(slots=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.
"""
factory = attr()
def make_class(name, attrs, **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 attributes_arguments: Passed unmodified to :func:`attr.s`.
:return: A new class with *attrs*.
:rtype: type
"""
if isinstance(attrs, dict):
cls_dict = attrs
elif isinstance(attrs, (list, tuple)):
cls_dict = dict((a, attr()) for a in attrs)
else:
raise TypeError("attrs argument must be a dict or a list.")
return attributes(**attributes_arguments)(type(name, (object,), cls_dict))