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from __future__ import absolute_import, division, print_function
import copy
import hashlib
import inspect
import linecache
from ._compat import exec_, iteritems
from . import _config
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 self.__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: Value that is used if an ``attrs``-generated
``__init__`` is used and no value is passed while instantiating. If
the value an instance of :class:`Factory`, it callable will be use to
construct a new value (useful for mutable datatypes like lists or
dicts).
: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.
: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(cl, 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(cl.__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 cl.__dict__.items()
if isinstance(attr, _CountingAttr)]
else:
ca_list = [(name, ca)
for name, ca
in iteritems(these)]
cl.__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 cl.__attrs_attrs__:
if these is None and a not in super_cls:
setattr(cl, a.name, a)
if had_default is True and a.default is NOTHING:
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:
had_default = True
def attributes(maybe_cl=None, these=None, repr_ns=None,
repr=True, cmp=True, hash=True, init=True):
"""
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 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 repr: Create a ``__repr__`` method with a human readable
represantation of ``attrs`` attributes..
:type repr: bool
:param 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*!
:type cmp: bool
:param hash: Create a ``__hash__`` method that returns the :func:`hash` of
a tuple of all ``attrs`` attribute values.
:type hash: bool
:param init: Create a ``__init__`` method that initialiazes the ``attrs``
attributes. Leading underscores are stripped for the argument name.
:type init: bool
"""
def wrap(cl):
if getattr(cl, "__class__", None) is None:
raise TypeError("attrs only works with new-style classes.")
_transform_attrs(cl, these)
if repr is True:
cl = _add_repr(cl, ns=repr_ns)
if cmp is True:
cl = _add_cmp(cl)
if hash is True:
cl = _add_hash(cl)
if init is True:
cl = _add_init(cl)
return cl
# 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_cl is None:
return wrap
else:
return wrap(maybe_cl)
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(cl, attrs=None):
"""
Add a hash method to *cl*.
"""
if attrs is None:
attrs = [a for a in cl.__attrs_attrs__ if a.hash]
def hash_(self):
"""
Automatically created by attrs.
"""
return hash(_attrs_to_tuple(self, attrs))
cl.__hash__ = hash_
return cl
def _add_cmp(cl, attrs=None):
"""
Add comparison methods to *cl*.
"""
if attrs is None:
attrs = [a for a in cl.__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
cl.__eq__ = eq
cl.__ne__ = ne
cl.__lt__ = lt
cl.__le__ = le
cl.__gt__ = gt
cl.__ge__ = ge
return cl
def _add_repr(cl, ns=None, attrs=None):
"""
Add a repr method to *cl*.
"""
if attrs is None:
attrs = [a for a in cl.__attrs_attrs__ if a.repr]
def repr_(self):
"""
Automatically created by attrs.
"""
real_cl = self.__class__
if ns is None:
qualname = getattr(real_cl, "__qualname__", None)
if qualname is not None:
class_name = qualname.rsplit(">.", 1)[-1]
else:
class_name = real_cl.__name__
else:
class_name = ns + "." + real_cl.__name__
return "{0}({1})".format(
class_name,
", ".join(a.name + "=" + repr(getattr(self, a.name))
for a in attrs)
)
cl.__repr__ = repr_
return cl
def _add_init(cl):
attrs = [a for a in cl.__attrs_attrs__ if a.init]
# 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 = _attrs_to_script(attrs)
locs = {}
bytecode = compile(script, unique_filename, "exec")
attr_dict = dict((a.name, a) for a in attrs)
exec_(bytecode, {"NOTHING": NOTHING,
"attr_dict": attr_dict,
"validate": validate,
"_convert": _convert}, 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
)
cl.__init__ = init
return cl
def fields(cl):
"""
Returns the tuple of ``attrs`` attributes for a class.
:param cl: Class to introspect.
:type cl: class
:raise TypeError: If *cl* is not a class.
:raise ValueError: If *cl* is not an ``attrs`` class.
:rtype: tuple of :class:`attr.Attribute`
"""
if not inspect.isclass(cl):
raise TypeError("Passed object must be a class.")
attrs = getattr(cl, "__attrs_attrs__", None)
if attrs is None:
raise ValueError("{cl!r} is not an attrs-decorated class.".format(
cl=cl
))
return copy.deepcopy(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 inst.__class__.__attrs_attrs__:
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 fields(inst.__class__):
if a.convert is not None:
setattr(inst, a.name, a.convert(getattr(inst, a.name)))
def _attrs_to_script(attrs):
"""
Return a valid Python script of an initializer for *attrs*.
"""
lines = []
args = []
has_validator = False
has_convert = False
for a in attrs:
if a.validator is not None:
has_validator = True
if a.convert is not None:
has_convert = True
attr_name = a.name
arg_name = a.name.lstrip("_")
if 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("self.{attr_name} = {arg_name}".format(
arg_name=arg_name,
attr_name=attr_name,
))
elif a.default is not NOTHING and isinstance(a.default, Factory):
args.append("{arg_name}=NOTHING".format(arg_name=arg_name))
lines.extend("""\
if {arg_name} is not NOTHING:
self.{attr_name} = {arg_name}
else:
self.{attr_name} = attr_dict["{attr_name}"].default.factory()"""
.format(attr_name=attr_name,
arg_name=arg_name)
.split("\n"))
else:
args.append(arg_name)
lines.append("self.{attr_name} = {arg_name}".format(
attr_name=attr_name,
arg_name=arg_name,
))
if has_convert:
lines.append("_convert(self)")
if has_validator:
lines.append("validate(self)")
return """\
def __init__(self, {args}):
{setters}
""".format(
args=", ".join(args),
setters="\n ".join(lines) if lines else "pass",
)
class Attribute(object):
"""
*Read-only* representation of an attribute.
:attribute name: The name of the attribute.
Plus *all* arguments of :func:`attr.ib`.
"""
_attributes = [
"name", "default", "validator", "repr", "cmp", "hash", "init",
"convert"
] # we can't use ``attrs`` so we have to cheat a little.
_optional = {"convert": None}
def __init__(self, **kw):
if len(kw) > len(Attribute._attributes):
raise TypeError("Too many arguments.")
for a in Attribute._attributes:
try:
setattr(self, a, kw[a])
except KeyError:
if a in Attribute._optional:
setattr(self, a, self._optional[a])
else:
raise TypeError("Missing argument '{arg}'.".format(arg=a))
@classmethod
def from_counting_attr(cl, name, ca):
return cl(name=name,
**dict((k, getattr(ca, k))
for k
in Attribute._attributes
if k != "name"))
_a = [Attribute(name=name, default=NOTHING, validator=None,
repr=True, cmp=True, hash=True, init=True)
for name in Attribute._attributes]
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
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):
cl_dict = attrs
elif isinstance(attrs, (list, tuple)):
cl_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,), cl_dict))
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