Viewing file:  _utilities.py (4.35 KB) -rw-r--r--
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from weakref import ref
from blinker._saferef import BoundMethodWeakref
try:
callable
except NameError:
def callable(object):
return hasattr(object, '__call__')
try:
from collections import defaultdict
except:
class defaultdict(dict):
def __init__(self, default_factory=None, *a, **kw):
if (default_factory is not None and
not hasattr(default_factory, '__call__')):
raise TypeError('first argument must be callable')
dict.__init__(self, *a, **kw)
self.default_factory = default_factory
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
return self.__missing__(key)
def __missing__(self, key):
if self.default_factory is None:
raise KeyError(key)
self[key] = value = self.default_factory()
return value
def __reduce__(self):
if self.default_factory is None:
args = tuple()
else:
args = self.default_factory,
return type(self), args, None, None, self.items()
def copy(self):
return self.__copy__()
def __copy__(self):
return type(self)(self.default_factory, self)
def __deepcopy__(self, memo):
import copy
return type(self)(self.default_factory,
copy.deepcopy(self.items()))
def __repr__(self):
return 'defaultdict(%s, %s)' % (self.default_factory,
dict.__repr__(self))
try:
from contextlib import contextmanager
except ImportError:
def contextmanager(fn):
def oops(*args, **kw):
raise RuntimeError("Python 2.5 or above is required to use "
"context managers.")
oops.__name__ = fn.__name__
return oops
class _symbol(object):
def __init__(self, name):
"""Construct a new named symbol."""
self.__name__ = self.name = name
def __reduce__(self):
return symbol, (self.name,)
def __repr__(self):
return self.name
_symbol.__name__ = 'symbol'
class symbol(object):
"""A constant symbol.
>>> symbol('foo') is symbol('foo')
True
>>> symbol('foo')
foo
A slight refinement of the MAGICCOOKIE=object() pattern. The primary
advantage of symbol() is its repr(). They are also singletons.
Repeated calls of symbol('name') will all return the same instance.
"""
symbols = {}
def __new__(cls, name):
try:
return cls.symbols[name]
except KeyError:
return cls.symbols.setdefault(name, _symbol(name))
try:
text = (str, unicode)
except NameError:
text = str
def hashable_identity(obj):
if hasattr(obj, '__func__'):
return (id(obj.__func__), id(obj.__self__))
elif hasattr(obj, 'im_func'):
return (id(obj.im_func), id(obj.im_self))
elif isinstance(obj, text):
return obj
else:
return id(obj)
WeakTypes = (ref, BoundMethodWeakref)
class annotatable_weakref(ref):
"""A weakref.ref that supports custom instance attributes."""
def reference(object, callback=None, **annotations):
"""Return an annotated weak ref."""
if callable(object):
weak = callable_reference(object, callback)
else:
weak = annotatable_weakref(object, callback)
for key, value in annotations.items():
setattr(weak, key, value)
return weak
def callable_reference(object, callback=None):
"""Return an annotated weak ref, supporting bound instance methods."""
if hasattr(object, 'im_self') and object.im_self is not None:
return BoundMethodWeakref(target=object, on_delete=callback)
elif hasattr(object, '__self__') and object.__self__ is not None:
return BoundMethodWeakref(target=object, on_delete=callback)
return annotatable_weakref(object, callback)
class lazy_property(object):
"""A @property that is only evaluated once."""
def __init__(self, deferred):
self._deferred = deferred
self.__doc__ = deferred.__doc__
def __get__(self, obj, cls):
if obj is None:
return self
value = self._deferred(obj)
setattr(obj, self._deferred.__name__, value)
return value
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