Flask中全局变量的实现

class AppContext(object):
"""The application context binds an application object implicitly
to the current thread or greenlet, similar to how the
:class:`RequestContext` binds request information. The application
context is also implicitly created if a request context is created
but the application is not on top of the individual application
context.
""" def __init__(self, app):
self.app = app
self.url_adapter = app.create_url_adapter(None)
self.g = app.app_ctx_globals_class() # Like request context, app contexts can be pushed multiple times
# but there a basic "refcount" is enough to track them.
self._refcnt = 0 def push(self):
"""Binds the app context to the current context."""
self._refcnt += 1
if hasattr(sys, 'exc_clear'):
sys.exc_clear()
_app_ctx_stack.push(self)
appcontext_pushed.send(self.app) def pop(self, exc=_sentinel):
"""Pops the app context."""
self._refcnt -= 1
if self._refcnt <= 0:
if exc is _sentinel:
exc = sys.exc_info()[1]
self.app.do_teardown_appcontext(exc)
rv = _app_ctx_stack.pop()
assert rv is self, 'Popped wrong app context. (%r instead of %r)' \
% (rv, self)
appcontext_popped.send(self.app) def __enter__(self):
self.push()
return self def __exit__(self, exc_type, exc_value, tb):
self.pop(exc_value) if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None:
reraise(exc_type, exc_value, tb)

def _lookup_app_object(name):
top = _app_ctx_stack.top
if top is None:
raise RuntimeError(_app_ctx_err_msg)
return getattr(top, name)def _find_app():
top = _app_ctx_stack.top
if top is None:
raise RuntimeError(_app_ctx_err_msg)
return top.app_app_ctx_stack = LocalStack()
current_app = LocalProxy(_find_app)

class Local(object):
__slots__ = ('__storage__', '__ident_func__') def __init__(self):
object.__setattr__(self, '__storage__', {})
object.__setattr__(self, '__ident_func__', get_ident) def __iter__(self):
return iter(self.__storage__.items()) def __call__(self, proxy):
"""Create a proxy for a name."""
return LocalProxy(self, proxy) def __release_local__(self):
self.__storage__.pop(self.__ident_func__(), None) def __getattr__(self, name):
try:
return self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name) def __setattr__(self, name, value):
ident = self.__ident_func__()
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value} def __delattr__(self, name):
try:
del self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)

class LocalStack(object): def __init__(self):
self._local = Local() def __release_local__(self):
self._local.__release_local__() def _get__ident_func__(self):
return self._local.__ident_func__ def _set__ident_func__(self, value):
object.__setattr__(self._local, '__ident_func__', value)
__ident_func__ = property(_get__ident_func__, _set__ident_func__)
del _get__ident_func__, _set__ident_func__ def __call__(self):
def _lookup():
rv = self.top
if rv is None:
raise RuntimeError('object unbound')
return rv
return LocalProxy(_lookup) def push(self, obj):
"""Pushes a new item to the stack"""
rv = getattr(self._local, 'stack', None)
if rv is None:
self._local.stack = rv = []
rv.append(obj)
return rv def pop(self):
"""Removes the topmost item from the stack, will return the
old value or `None` if the stack was already empty.
"""
stack = getattr(self._local, 'stack', None)
if stack is None:
return None
elif len(stack) == 1:
release_local(self._local)
return stack[-1]
else:
return stack.pop() @property
def top(self):
"""The topmost item on the stack. If the stack is empty,
`None` is returned.
"""
try:
return self._local.stack[-1]
except (AttributeError, IndexError):
return None

class LocalProxy(object): """Acts as a proxy for a werkzeug local. Forwards all operations to
a proxied object. The only operations not supported for forwarding
are right handed operands and any kind of assignment. Example usage:: from werkzeug.local import Local
l = Local() # these are proxies
request = l('request')
user = l('user') from werkzeug.local import LocalStack
_response_local = LocalStack() # this is a proxy
response = _response_local() Whenever something is bound to l.user / l.request the proxy objects
will forward all operations. If no object is bound a :exc:`RuntimeError`
will be raised. To create proxies to :class:`Local` or :class:`LocalStack` objects,
call the object as shown above. If you want to have a proxy to an
object looked up by a function, you can (as of Werkzeug 0.6.1) pass
a function to the :class:`LocalProxy` constructor:: session = LocalProxy(lambda: get_current_request().session) .. versionchanged:: 0.6.1
The class can be instanciated with a callable as well now.
"""
__slots__ = ('__local', '__dict__', '__name__') def __init__(self, local, name=None):
object.__setattr__(self, '_LocalProxy__local', local)
object.__setattr__(self, '__name__', name) def _get_current_object(self):
"""Return the current object. This is useful if you want the real
object behind the proxy at a time for performance reasons or because
you want to pass the object into a different context.
"""
if not hasattr(self.__local, '__release_local__'):
return self.__local()
try:
return getattr(self.__local, self.__name__)
except AttributeError:
raise RuntimeError('no object bound to %s' % self.__name__) @property
def __dict__(self):
try:
return self._get_current_object().__dict__
except RuntimeError:
raise AttributeError('__dict__') def __repr__(self):
try:
obj = self._get_current_object()
except RuntimeError:
return '<%s unbound>' % self.__class__.__name__
return repr(obj) def __bool__(self):
try:
return bool(self._get_current_object())
except RuntimeError:
return False def __unicode__(self):
try:
return unicode(self._get_current_object()) # noqa
except RuntimeError:
return repr(self) def __dir__(self):
try:
return dir(self._get_current_object())
except RuntimeError:
return [] def __getattr__(self, name):
if name == '__members__':
return dir(self._get_current_object())
return getattr(self._get_current_object(), name) def __setitem__(self, key, value):
self._get_current_object()[key] = value def __delitem__(self, key):
del self._get_current_object()[key] if PY2:
__getslice__ = lambda x, i, j: x._get_current_object()[i:j] def __setslice__(self, i, j, seq):
self._get_current_object()[i:j] = seq def __delslice__(self, i, j):
del self._get_current_object()[i:j] __setattr__ = lambda x, n, v: setattr(x._get_current_object(), n, v)
__delattr__ = lambda x, n: delattr(x._get_current_object(), n)
__str__ = lambda x: str(x._get_current_object())
__lt__ = lambda x, o: x._get_current_object() < o
__le__ = lambda x, o: x._get_current_object() <= o
__eq__ = lambda x, o: x._get_current_object() == o
__ne__ = lambda x, o: x._get_current_object() != o
__gt__ = lambda x, o: x._get_current_object() > o
__ge__ = lambda x, o: x._get_current_object() >= o
__cmp__ = lambda x, o: cmp(x._get_current_object(), o) # noqa
__hash__ = lambda x: hash(x._get_current_object())
__call__ = lambda x, *a, **kw: x._get_current_object()(*a, **kw)
__len__ = lambda x: len(x._get_current_object())
__getitem__ = lambda x, i: x._get_current_object()[i]
__iter__ = lambda x: iter(x._get_current_object())
__contains__ = lambda x, i: i in x._get_current_object()
__add__ = lambda x, o: x._get_current_object() + o
__sub__ = lambda x, o: x._get_current_object() - o
__mul__ = lambda x, o: x._get_current_object() * o
__floordiv__ = lambda x, o: x._get_current_object() // o
__mod__ = lambda x, o: x._get_current_object() % o
__divmod__ = lambda x, o: x._get_current_object().__divmod__(o)
__pow__ = lambda x, o: x._get_current_object() ** o
__lshift__ = lambda x, o: x._get_current_object() << o
__rshift__ = lambda x, o: x._get_current_object() >> o
__and__ = lambda x, o: x._get_current_object() & o
__xor__ = lambda x, o: x._get_current_object() ^ o
__or__ = lambda x, o: x._get_current_object() | o
__div__ = lambda x, o: x._get_current_object().__div__(o)
__truediv__ = lambda x, o: x._get_current_object().__truediv__(o)
__neg__ = lambda x: -(x._get_current_object())
__pos__ = lambda x: +(x._get_current_object())
__abs__ = lambda x: abs(x._get_current_object())
__invert__ = lambda x: ~(x._get_current_object())
__complex__ = lambda x: complex(x._get_current_object())
__int__ = lambda x: int(x._get_current_object())
__long__ = lambda x: long(x._get_current_object()) # noqa
__float__ = lambda x: float(x._get_current_object())
__oct__ = lambda x: oct(x._get_current_object())
__hex__ = lambda x: hex(x._get_current_object())
__index__ = lambda x: x._get_current_object().__index__()
__coerce__ = lambda x, o: x._get_current_object().__coerce__(x, o)
__enter__ = lambda x: x._get_current_object().__enter__()
__exit__ = lambda x, *a, **kw: x._get_current_object().__exit__(*a, **kw)
__radd__ = lambda x, o: o + x._get_current_object()
__rsub__ = lambda x, o: o - x._get_current_object()
__rmul__ = lambda x, o: o * x._get_current_object()
__rdiv__ = lambda x, o: o / x._get_current_object()
if PY2:
__rtruediv__ = lambda x, o: x._get_current_object().__rtruediv__(o)
else:
__rtruediv__ = __rdiv__
__rfloordiv__ = lambda x, o: o // x._get_current_object()
__rmod__ = lambda x, o: o % x._get_current_object()
__rdivmod__ = lambda x, o: x._get_current_object().__rdivmod__(o)