text: """Event loop and event loop policy."""
  
  __all__ = ['AbstractEventLoopPolicy',
             'AbstractEventLoop', 'AbstractServer',
             'Handle', 'TimerHandle',
             'get_event_loop_policy', 'set_event_loop_policy',
             'get_event_loop', 'set_event_loop', 'new_event_loop',
             'get_child_watcher', 'set_child_watcher',
             ]
  
  import subprocess
  import threading
  import socket
  
  
  class Handle:
      """Object returned by callback registration methods."""
  
      __slots__ = ['_callback', '_args', '_cancelled', '_loop']
  
      def __init__(self, callback, args, loop):
          assert not isinstance(callback, Handle), 'A Handle is not a callback'
          self._loop = loop
          self._callback = callback
          self._args = args
          self._cancelled = False
  
      def __repr__(self):
          res = 'Handle({}, {})'.format(self._callback, self._args)
          if self._cancelled:
              res += '<cancelled>'
          return res
  
      def cancel(self):
          self._cancelled = True
  
      def _run(self):
          try:
              self._callback(*self._args)
          except Exception as exc:
              msg = 'Exception in callback {}{!r}'.format(self._callback,
                                                          self._args)
              self._loop.call_exception_handler({
                  'message': msg,
                  'exception': exc,
                  'handle': self,
              })
          self = None  # Needed to break cycles when an exception occurs.
  
  
  class TimerHandle(Handle):
      """Object returned by timed callback registration methods."""
  
      __slots__ = ['_when']
  
      def __init__(self, when, callback, args, loop):
          assert when is not None
          super().__init__(callback, args, loop)
  
          self._when = when
  
      def __repr__(self):
          res = 'TimerHandle({}, {}, {})'.format(self._when,
                                                 self._callback,
                                                 self._args)
          if self._cancelled:
              res += '<cancelled>'
  
          return res
  
      def __hash__(self):
          return hash(self._when)
  
      def __lt__(self, other):
          return self._when < other._when
  
      def __le__(self, other):
          if self._when < other._when:
              return True
          return self.__eq__(other)
  
      def __gt__(self, other):
          return self._when > other._when
  
      def __ge__(self, other):
          if self._when > other._when:
              return True
          return self.__eq__(other)
  
      def __eq__(self, other):
          if isinstance(other, TimerHandle):
              return (self._when == other._when and
                      self._callback == other._callback and
                      self._args == other._args and
                      self._cancelled == other._cancelled)
          return NotImplemented
  
      def __ne__(self, other):
          equal = self.__eq__(other)
          return NotImplemented if equal is NotImplemented else not equal
  
  
  class AbstractServer:
      """Abstract server returned by create_server()."""
  
      def close(self):
          """Stop serving.  This leaves existing connections open."""
          return NotImplemented
  
      def wait_closed(self):
          """Coroutine to wait until service is closed."""
          return NotImplemented
  
  
  class AbstractEventLoop:
      """Abstract event loop."""
  
      # Running and stopping the event loop.
  
      def run_forever(self):
          """Run the event loop until stop() is called."""
          raise NotImplementedError
  
      def run_until_complete(self, future):
          """Run the event loop until a Future is done.
  
          Return the Future's result, or raise its exception.
          """
          raise NotImplementedError
  
      def stop(self):
          """Stop the event loop as soon as reasonable.
  
          Exactly how soon that is may depend on the implementation, but
          no more I/O callbacks should be scheduled.
          """
          raise NotImplementedError
  
      def is_running(self):
          """Return whether the event loop is currently running."""
          raise NotImplementedError
  
      def close(self):
          """Close the loop.
  
          The loop should not be running.
  
          This is idempotent and irreversible.
  
          No other methods should be called after this one.
          """
          raise NotImplementedError
  
      # Methods scheduling callbacks.  All these return Handles.
  
      def call_soon(self, callback, *args):
          return self.call_later(0, callback, *args)
  
      def call_later(self, delay, callback, *args):
          raise NotImplementedError
  
      def call_at(self, when, callback, *args):
          raise NotImplementedError
  
      def time(self):
          raise NotImplementedError
  
      # Methods for interacting with threads.
  
      def call_soon_threadsafe(self, callback, *args):
          raise NotImplementedError
  
      def run_in_executor(self, executor, callback, *args):
          raise NotImplementedError
  
      def set_default_executor(self, executor):
          raise NotImplementedError
  
      # Network I/O methods returning Futures.
  
      def getaddrinfo(self, host, port, *, family=0, type=0, proto=0, flags=0):
          raise NotImplementedError
  
      def getnameinfo(self, sockaddr, flags=0):
          raise NotImplementedError
  
      def create_connection(self, protocol_factory, host=None, port=None, *,
                            ssl=None, family=0, proto=0, flags=0, sock=None,
                            local_addr=None, server_hostname=None):
          raise NotImplementedError
  
      def create_server(self, protocol_factory, host=None, port=None, *,
                        family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE,
                        sock=None, backlog=100, ssl=None, reuse_address=None):
          """A coroutine which creates a TCP server bound to host and port.
  
          The return value is a Server object which can be used to stop
          the service.
  
          If host is an empty string or None all interfaces are assumed
          and a list of multiple sockets will be returned (most likely
          one for IPv4 and another one for IPv6).
  
          family can be set to either AF_INET or AF_INET6 to force the
          socket to use IPv4 or IPv6. If not set it will be determined
          from host (defaults to AF_UNSPEC).
  
          flags is a bitmask for getaddrinfo().
  
          sock can optionally be specified in order to use a preexisting
          socket object.
  
          backlog is the maximum number of queued connections passed to
          listen() (defaults to 100).
  
          ssl can be set to an SSLContext to enable SSL over the
          accepted connections.
  
          reuse_address tells the kernel to reuse a local socket in
          TIME_WAIT state, without waiting for its natural timeout to
          expire. If not specified will automatically be set to True on
          UNIX.
          """
          raise NotImplementedError
  
      def create_unix_connection(self, protocol_factory, path, *,
                                 ssl=None, sock=None,
                                 server_hostname=None):
          raise NotImplementedError
  
      def create_unix_server(self, protocol_factory, path, *,
                             sock=None, backlog=100, ssl=None):
          """A coroutine which creates a UNIX Domain Socket server.
  
          The return value is a Server object, which can be used to stop
          the service.
  
          path is a str, representing a file systsem path to bind the
          server socket to.
  
          sock can optionally be specified in order to use a preexisting
          socket object.
  
          backlog is the maximum number of queued connections passed to
          listen() (defaults to 100).
  
          ssl can be set to an SSLContext to enable SSL over the
          accepted connections.
          """
          raise NotImplementedError
  
      def create_datagram_endpoint(self, protocol_factory,
                                   local_addr=None, remote_addr=None, *,
                                   family=0, proto=0, flags=0):
          raise NotImplementedError
  
      # Pipes and subprocesses.
  
      def connect_read_pipe(self, protocol_factory, pipe):
          """Register read pipe in event loop.
  
          protocol_factory should instantiate object with Protocol interface.
          pipe is file-like object already switched to nonblocking.
          Return pair (transport, protocol), where transport support
          ReadTransport interface."""
          # The reason to accept file-like object instead of just file descriptor
          # is: we need to own pipe and close it at transport finishing
          # Can got complicated errors if pass f.fileno(),
          # close fd in pipe transport then close f and vise versa.
          raise NotImplementedError
  
      def connect_write_pipe(self, protocol_factory, pipe):
          """Register write pipe in event loop.
  
          protocol_factory should instantiate object with BaseProtocol interface.
          Pipe is file-like object already switched to nonblocking.
          Return pair (transport, protocol), where transport support
          WriteTransport interface."""
          # The reason to accept file-like object instead of just file descriptor
          # is: we need to own pipe and close it at transport finishing
          # Can got complicated errors if pass f.fileno(),
          # close fd in pipe transport then close f and vise versa.
          raise NotImplementedError
  
      def subprocess_shell(self, protocol_factory, cmd, *, stdin=subprocess.PIPE,
                           stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                           **kwargs):
          raise NotImplementedError
  
      def subprocess_exec(self, protocol_factory, *args, stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                          **kwargs):
          raise NotImplementedError
  
      # Ready-based callback registration methods.
      # The add_*() methods return None.
      # The remove_*() methods return True if something was removed,
      # False if there was nothing to delete.
  
      def add_reader(self, fd, callback, *args):
          raise NotImplementedError
  
      def remove_reader(self, fd):
          raise NotImplementedError
  
      def add_writer(self, fd, callback, *args):
          raise NotImplementedError
  
      def remove_writer(self, fd):
          raise NotImplementedError
  
      # Completion based I/O methods returning Futures.
  
      def sock_recv(self, sock, nbytes):
          raise NotImplementedError
  
      def sock_sendall(self, sock, data):
          raise NotImplementedError
  
      def sock_connect(self, sock, address):
          raise NotImplementedError
  
      def sock_accept(self, sock):
          raise NotImplementedError
  
      # Signal handling.
  
      def add_signal_handler(self, sig, callback, *args):
          raise NotImplementedError
  
      def remove_signal_handler(self, sig):
          raise NotImplementedError
  
      # Error handlers.
  
      def set_exception_handler(self, handler):
          raise NotImplementedError
  
      def default_exception_handler(self, context):
          raise NotImplementedError
  
      def call_exception_handler(self, context):
          raise NotImplementedError
  
      # Debug flag management.
  
      def get_debug(self):
          raise NotImplementedError
  
      def set_debug(self, enabled):
          raise NotImplementedError
  
  
  class AbstractEventLoopPolicy:
      """Abstract policy for accessing the event loop."""
  
      def get_event_loop(self):
          """XXX"""
          raise NotImplementedError
  
      def set_event_loop(self, loop):
          """XXX"""
          raise NotImplementedError
  
      def new_event_loop(self):
          """XXX"""
          raise NotImplementedError
  
      # Child processes handling (Unix only).
  
      def get_child_watcher(self):
          """XXX"""
          raise NotImplementedError
  
      def set_child_watcher(self, watcher):
          """XXX"""
          raise NotImplementedError
  
  
  class BaseDefaultEventLoopPolicy(AbstractEventLoopPolicy):
      """Default policy implementation for accessing the event loop.
  
      In this policy, each thread has its own event loop.  However, we
      only automatically create an event loop by default for the main
      thread; other threads by default have no event loop.
  
      Other policies may have different rules (e.g. a single global
      event loop, or automatically creating an event loop per thread, or
      using some other notion of context to which an event loop is
      associated).
      """
  
      _loop_factory = None
  
      class _Local(threading.local):
          _loop = None
          _set_called = False
  
      def __init__(self):
          self._local = self._Local()
  
      def get_event_loop(self):
          """Get the event loop.
  
          This may be None or an instance of EventLoop.
          """
          if (self._local._loop is None and
              not self._local._set_called and
              isinstance(threading.current_thread(), threading._MainThread)):
              self.set_event_loop(self.new_event_loop())
          assert self._local._loop is not None, \
                 ('There is no current event loop in thread %r.' %
                  threading.current_thread().name)
          return self._local._loop
  
      def set_event_loop(self, loop):
          """Set the event loop."""
          self._local._set_called = True
          assert loop is None or isinstance(loop, AbstractEventLoop)
          self._local._loop = loop
  
      def new_event_loop(self):
          """Create a new event loop.
  
          You must call set_event_loop() to make this the current event
          loop.
          """
          return self._loop_factory()
  
  
  # Event loop policy.  The policy itself is always global, even if the
  # policy's rules say that there is an event loop per thread (or other
  # notion of context).  The default policy is installed by the first
  # call to get_event_loop_policy().
  _event_loop_policy = None
  
  # Lock for protecting the on-the-fly creation of the event loop policy.
  _lock = threading.Lock()
  
  
  def _init_event_loop_policy():
      global _event_loop_policy
      with _lock:
          if _event_loop_policy is None:  # pragma: no branch
              from . import DefaultEventLoopPolicy
              _event_loop_policy = DefaultEventLoopPolicy()
  
  
  def get_event_loop_policy():
      """XXX"""
      if _event_loop_policy is None:
          _init_event_loop_policy()
      return _event_loop_policy
  
  
  def set_event_loop_policy(policy):
      """XXX"""
      global _event_loop_policy
      assert policy is None or isinstance(policy, AbstractEventLoopPolicy)
      _event_loop_policy = policy
  
  
  def get_event_loop():
      """XXX"""
      return get_event_loop_policy().get_event_loop()
  
  
  def set_event_loop(loop):
      """XXX"""
      get_event_loop_policy().set_event_loop(loop)
  
  
  def new_event_loop():
      """XXX"""
      return get_event_loop_policy().new_event_loop()
  
  
  def get_child_watcher():
      """XXX"""
      return get_event_loop_policy().get_child_watcher()
  
  
  def set_child_watcher(watcher):
      """XXX"""
      return get_event_loop_policy().set_child_watcher(watcher)
  