/usr/lib/python2.7/dist-packages/eventlet/event.py is in python-eventlet 0.13.0-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 | from eventlet import hubs
from eventlet.support import greenlets as greenlet
__all__ = ['Event']
class NOT_USED:
def __repr__(self):
return 'NOT_USED'
NOT_USED = NOT_USED()
class Event(object):
"""An abstraction where an arbitrary number of coroutines
can wait for one event from another.
Events are similar to a Queue that can only hold one item, but differ
in two important ways:
1. calling :meth:`send` never unschedules the current greenthread
2. :meth:`send` can only be called once; create a new event to send again.
They are good for communicating results between coroutines, and
are the basis for how
:meth:`GreenThread.wait() <eventlet.greenthread.GreenThread.wait>`
is implemented.
>>> from eventlet import event
>>> import eventlet
>>> evt = event.Event()
>>> def baz(b):
... evt.send(b + 1)
...
>>> _ = eventlet.spawn_n(baz, 3)
>>> evt.wait()
4
"""
_result = None
_exc = None
def __init__(self):
self._waiters = set()
self.reset()
def __str__(self):
params = (self.__class__.__name__, hex(id(self)),
self._result, self._exc, len(self._waiters))
return '<%s at %s result=%r _exc=%r _waiters[%d]>' % params
def reset(self):
# this is kind of a misfeature and doesn't work perfectly well,
# it's better to create a new event rather than reset an old one
# removing documentation so that we don't get new use cases for it
assert self._result is not NOT_USED, 'Trying to re-reset() a fresh event.'
self._result = NOT_USED
self._exc = None
def ready(self):
""" Return true if the :meth:`wait` call will return immediately.
Used to avoid waiting for things that might take a while to time out.
For example, you can put a bunch of events into a list, and then visit
them all repeatedly, calling :meth:`ready` until one returns ``True``,
and then you can :meth:`wait` on that one."""
return self._result is not NOT_USED
def has_exception(self):
return self._exc is not None
def has_result(self):
return self._result is not NOT_USED and self._exc is None
def poll(self, notready=None):
if self.ready():
return self.wait()
return notready
# QQQ make it return tuple (type, value, tb) instead of raising
# because
# 1) "poll" does not imply raising
# 2) it's better not to screw up caller's sys.exc_info() by default
# (e.g. if caller wants to calls the function in except or finally)
def poll_exception(self, notready=None):
if self.has_exception():
return self.wait()
return notready
def poll_result(self, notready=None):
if self.has_result():
return self.wait()
return notready
def wait(self):
"""Wait until another coroutine calls :meth:`send`.
Returns the value the other coroutine passed to
:meth:`send`.
>>> from eventlet import event
>>> import eventlet
>>> evt = event.Event()
>>> def wait_on():
... retval = evt.wait()
... print "waited for", retval
>>> _ = eventlet.spawn(wait_on)
>>> evt.send('result')
>>> eventlet.sleep(0)
waited for result
Returns immediately if the event has already
occured.
>>> evt.wait()
'result'
"""
current = greenlet.getcurrent()
if self._result is NOT_USED:
self._waiters.add(current)
try:
return hubs.get_hub().switch()
finally:
self._waiters.discard(current)
if self._exc is not None:
current.throw(*self._exc)
return self._result
def send(self, result=None, exc=None):
"""Makes arrangements for the waiters to be woken with the
result and then returns immediately to the parent.
>>> from eventlet import event
>>> import eventlet
>>> evt = event.Event()
>>> def waiter():
... print 'about to wait'
... result = evt.wait()
... print 'waited for', result
>>> _ = eventlet.spawn(waiter)
>>> eventlet.sleep(0)
about to wait
>>> evt.send('a')
>>> eventlet.sleep(0)
waited for a
It is an error to call :meth:`send` multiple times on the same event.
>>> evt.send('whoops')
Traceback (most recent call last):
...
AssertionError: Trying to re-send() an already-triggered event.
Use :meth:`reset` between :meth:`send` s to reuse an event object.
"""
assert self._result is NOT_USED, 'Trying to re-send() an already-triggered event.'
self._result = result
if exc is not None and not isinstance(exc, tuple):
exc = (exc, )
self._exc = exc
hub = hubs.get_hub()
for waiter in self._waiters:
hub.schedule_call_global(
0, self._do_send, self._result, self._exc, waiter)
def _do_send(self, result, exc, waiter):
if waiter in self._waiters:
if exc is None:
waiter.switch(result)
else:
waiter.throw(*exc)
def send_exception(self, *args):
"""Same as :meth:`send`, but sends an exception to waiters.
The arguments to send_exception are the same as the arguments
to ``raise``. If a single exception object is passed in, it
will be re-raised when :meth:`wait` is called, generating a
new stacktrace.
>>> from eventlet import event
>>> evt = event.Event()
>>> evt.send_exception(RuntimeError())
>>> evt.wait()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "eventlet/event.py", line 120, in wait
current.throw(*self._exc)
RuntimeError
If it's important to preserve the entire original stack trace,
you must pass in the entire :func:`sys.exc_info` tuple.
>>> import sys
>>> evt = event.Event()
>>> try:
... raise RuntimeError()
... except RuntimeError:
... evt.send_exception(*sys.exc_info())
...
>>> evt.wait()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "eventlet/event.py", line 120, in wait
current.throw(*self._exc)
File "<stdin>", line 2, in <module>
RuntimeError
Note that doing so stores a traceback object directly on the
Event object, which may cause reference cycles. See the
:func:`sys.exc_info` documentation.
"""
# the arguments and the same as for greenlet.throw
return self.send(None, args)
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