zmq¶
Python bindings for 0MQ.
Basic Classes¶
Context
¶
-
class
zmq.
Context
(io_threads=1, **kwargs)¶ Create a zmq Context
A zmq Context creates sockets via its
ctx.socket
method.-
closed
¶ boolean - whether the context has been terminated. If True, you can no longer use this Context.
-
destroy
(linger=None)¶ ctx.destroy(linger=None)
Close all sockets associated with this context, and then terminate the context. If linger is specified, the LINGER sockopt of the sockets will be set prior to closing.
Warning
destroy involves calling
zmq_close()
, which is NOT threadsafe. If there are active sockets in other threads, this must not be called.
-
get
(option)¶ ctx.get(option)
Get the value of a context option.
See the 0MQ API documentation for zmq_ctx_get for details on specific options.
New in version libzmq-3.2.
New in version 13.0.
Parameters: option (int) – The option to get. Available values will depend on your version of libzmq. Examples include:
zmq.IO_THREADS, zmq.MAX_SOCKETS
Returns: optval – The value of the option as an integer. Return type: int
-
getsockopt
(opt)¶ get default socket options for new sockets created by this Context
New in version 13.0.
-
classmethod
instance
(io_threads=1)¶ Returns a global Context instance.
Most single-threaded applications have a single, global Context. Use this method instead of passing around Context instances throughout your code.
A common pattern for classes that depend on Contexts is to use a default argument to enable programs with multiple Contexts but not require the argument for simpler applications:
- class MyClass(object):
- def __init__(self, context=None):
- self.context = context or Context.instance()
-
set
(option, optval)¶ ctx.set(option, optval)
Set a context option.
See the 0MQ API documentation for zmq_ctx_set for details on specific options.
New in version libzmq-3.2.
New in version 13.0.
Parameters:
-
setsockopt
(opt, value)¶ set default socket options for new sockets created by this Context
New in version 13.0.
-
classmethod
shadow
(address)¶ Shadow an existing libzmq context
address is the integer address of the libzmq context or an FFI pointer to it.
New in version 14.1.
-
classmethod
shadow_pyczmq
(ctx)¶ Shadow an existing pyczmq context
ctx is the FFI zctx_t * pointer
New in version 14.1.
-
socket
(socket_type, **kwargs)¶ Create a Socket associated with this Context.
Parameters: - socket_type (int) – The socket type, which can be any of the 0MQ socket types: REQ, REP, PUB, SUB, PAIR, DEALER, ROUTER, PULL, PUSH, etc.
- kwargs – will be passed to the __init__ method of the socket class.
-
term
()¶ ctx.term()
Close or terminate the context.
This can be called to close the context by hand. If this is not called, the context will automatically be closed when it is garbage collected.
-
underlying
¶ The address of the underlying libzmq context
-
Socket
¶
-
class
zmq.
Socket
(*a, **kw)¶ The ZMQ socket object
To create a Socket, first create a Context:
ctx = zmq.Context.instance()
then call
ctx.socket(socket_type)
:s = ctx.socket(zmq.ROUTER)
-
closed
¶ boolean - whether the socket has been closed. If True, you can no longer use this Socket.
-
bind
(addr)¶ s.bind(addr)
Bind the socket to an address.
This causes the socket to listen on a network port. Sockets on the other side of this connection will use
Socket.connect(addr)
to connect to this socket.Parameters: addr (str) – The address string. This has the form ‘protocol://interface:port’, for example ‘tcp://127.0.0.1:5555’. Protocols supported include tcp, udp, pgm, epgm, inproc and ipc. If the address is unicode, it is encoded to utf-8 first.
-
bind_to_random_port
(addr, min_port=49152, max_port=65536, max_tries=100)¶ bind this socket to a random port in a range
If the port range is unspecified, the system will choose the port.
Parameters: - addr (str) – The address string without the port to pass to
Socket.bind()
. - min_port (int, optional) – The minimum port in the range of ports to try (inclusive).
- max_port (int, optional) – The maximum port in the range of ports to try (exclusive).
- max_tries (int, optional) – The maximum number of bind attempts to make.
Returns: port – The port the socket was bound to.
Return type: Raises: ZMQBindError
– if max_tries reached before successful bind- addr (str) – The address string without the port to pass to
-
close
(linger=None)¶ s.close(linger=None)
Close the socket.
If linger is specified, LINGER sockopt will be set prior to closing.
This can be called to close the socket by hand. If this is not called, the socket will automatically be closed when it is garbage collected.
-
connect
(addr)¶ s.connect(addr)
Connect to a remote 0MQ socket.
Parameters: addr (str) – The address string. This has the form ‘protocol://interface:port’, for example ‘tcp://127.0.0.1:5555’. Protocols supported are tcp, upd, pgm, inproc and ipc. If the address is unicode, it is encoded to utf-8 first.
-
disable_monitor
()¶ Shutdown the PAIR socket (created using get_monitor_socket) that is serving socket events.
New in version 14.4.
-
disconnect
(addr)¶ s.disconnect(addr)
Disconnect from a remote 0MQ socket (undoes a call to connect).
New in version libzmq-3.2.
New in version 13.0.
Parameters: addr (str) – The address string. This has the form ‘protocol://interface:port’, for example ‘tcp://127.0.0.1:5555’. Protocols supported are tcp, upd, pgm, inproc and ipc. If the address is unicode, it is encoded to utf-8 first.
-
get
(option)¶ s.get(option)
Get the value of a socket option.
See the 0MQ API documentation for details on specific options.
Parameters: option (int) – The option to get. Available values will depend on your version of libzmq. Examples include:
zmq.IDENTITY, HWM, LINGER, FD, EVENTS
Returns: optval – The value of the option as a bytestring or int. Return type: int or bytes
-
get_hwm
()¶ get the High Water Mark
On libzmq ≥ 3, this gets SNDHWM if available, otherwise RCVHWM
-
get_monitor_socket
(events=None, addr=None)¶ Return a connected PAIR socket ready to receive the event notifications.
New in version libzmq-4.0.
New in version 14.0.
Parameters: - events (bitfield (int) [default: ZMQ_EVENTS_ALL]) – The bitmask defining which events are wanted.
- addr (string [default: None]) – The optional endpoint for the monitoring sockets.
Returns: socket – The socket is already connected and ready to receive messages.
Return type: (PAIR)
-
get_string
(option, encoding='utf-8')¶ get the value of a socket option
See the 0MQ documentation for details on specific options.
Parameters: option (int) – The option to retrieve. Returns: optval – The value of the option as a unicode string. Return type: unicode string (unicode on py2, str on py3)
-
getsockopt
¶ s.get(option)
Get the value of a socket option.
See the 0MQ API documentation for details on specific options.
Parameters: option (int) – The option to get. Available values will depend on your version of libzmq. Examples include:
zmq.IDENTITY, HWM, LINGER, FD, EVENTS
Returns: optval – The value of the option as a bytestring or int. Return type: int or bytes
-
getsockopt_string
(option, encoding='utf-8')¶ get the value of a socket option
See the 0MQ documentation for details on specific options.
Parameters: option (int) – The option to retrieve. Returns: optval – The value of the option as a unicode string. Return type: unicode string (unicode on py2, str on py3)
-
hwm
¶ get the High Water Mark
On libzmq ≥ 3, this gets SNDHWM if available, otherwise RCVHWM
-
monitor
(addr, flags)¶ s.monitor(addr, flags)
Start publishing socket events on inproc. See libzmq docs for zmq_monitor for details.
While this function is available from libzmq 3.2, pyzmq cannot parse monitor messages from libzmq prior to 4.0.
Parameters: - addr (str) – The inproc url used for monitoring. Passing None as the addr will cause an existing socket monitor to be deregistered.
- events (int [default: zmq.EVENT_ALL]) – The zmq event bitmask for which events will be sent to the monitor.
-
poll
(timeout=None, flags=1)¶ poll the socket for events
The default is to poll forever for incoming events. Timeout is in milliseconds, if specified.
Parameters: - timeout (int [default: None]) – The timeout (in milliseconds) to wait for an event. If unspecified (or specified None), will wait forever for an event.
- flags (bitfield (int) [default: POLLIN]) – The event flags to poll for (any combination of POLLIN|POLLOUT). The default is to check for incoming events (POLLIN).
Returns: events – The events that are ready and waiting. Will be 0 if no events were ready by the time timeout was reached.
Return type: bitfield (int)
-
recv
(flags=0, copy=True, track=False)¶ s.recv(flags=0, copy=True, track=False)
Receive a message.
Parameters: - flags (int) – Any supported flag: NOBLOCK. If NOBLOCK is set, this method will raise a ZMQError with EAGAIN if a message is not ready. If NOBLOCK is not set, then this method will block until a message arrives.
- copy (bool) – Should the message be received in a copying or non-copying manner? If False a Frame object is returned, if True a string copy of message is returned.
- track (bool) – Should the message be tracked for notification that ZMQ has finished with it? (ignored if copy=True)
Returns: msg – The received message frame. If copy is False, then it will be a Frame, otherwise it will be bytes.
Return type: bytes, Frame
Raises: ZMQError
– for any of the reasons zmq_msg_recv might fail.
-
recv_json
(flags=0, **kwargs)¶ receive a Python object as a message using json to serialize
Keyword arguments are passed on to json.loads
Parameters: flags (int) – Any valid recv flag. Returns: obj – The Python object that arrives as a message. Return type: Python object
-
recv_multipart
(flags=0, copy=True, track=False)¶ receive a multipart message as a list of bytes or Frame objects
Parameters: - flags (int, optional) – Any supported flag: NOBLOCK. If NOBLOCK is set, this method will raise a ZMQError with EAGAIN if a message is not ready. If NOBLOCK is not set, then this method will block until a message arrives.
- copy (bool, optional) – Should the message frame(s) be received in a copying or non-copying manner? If False a Frame object is returned for each part, if True a copy of the bytes is made for each frame.
- track (bool, optional) – Should the message frame(s) be tracked for notification that ZMQ has finished with it? (ignored if copy=True)
Returns: msg_parts – A list of frames in the multipart message; either Frames or bytes, depending on copy.
Return type:
-
recv_pyobj
(flags=0)¶ receive a Python object as a message using pickle to serialize
Parameters: flags (int) – Any valid recv flag. Returns: obj – The Python object that arrives as a message. Return type: Python object
-
recv_string
(flags=0, encoding='utf-8')¶ receive a unicode string, as sent by send_string
Parameters: - flags (int) – Any valid recv flag.
- encoding (str [default: 'utf-8']) – The encoding to be used
Returns: s – The Python unicode string that arrives as encoded bytes.
Return type: unicode string (unicode on py2, str on py3)
-
send
(data, flags=0, copy=True, track=False)¶ s.send(data, flags=0, copy=True, track=False)
Send a message on this socket.
This queues the message to be sent by the IO thread at a later time.
Parameters: - data (object, str, Frame) – The content of the message.
- flags (int) – Any supported flag: NOBLOCK, SNDMORE.
- copy (bool) – Should the message be sent in a copying or non-copying manner.
- track (bool) – Should the message be tracked for notification that ZMQ has finished with it? (ignored if copy=True)
Returns: - None (if copy or not track) – None if message was sent, raises an exception otherwise.
- MessageTracker (if track and not copy) – a MessageTracker object, whose pending property will be True until the send is completed.
Raises: TypeError
– If a unicode object is passedValueError
– If track=True, but an untracked Frame is passed.ZMQError
– If the send does not succeed for any reason.
-
send_json
(obj, flags=0, **kwargs)¶ send a Python object as a message using json to serialize
Keyword arguments are passed on to json.dumps
Parameters: - obj (Python object) – The Python object to send
- flags (int) – Any valid send flag
-
send_multipart
(msg_parts, flags=0, copy=True, track=False)¶ send a sequence of buffers as a multipart message
The zmq.SNDMORE flag is added to all msg parts before the last.
Parameters: - msg_parts (iterable) – A sequence of objects to send as a multipart message. Each element can be any sendable object (Frame, bytes, buffer-providers)
- flags (int, optional) – SNDMORE is handled automatically for frames before the last.
- copy (bool, optional) – Should the frame(s) be sent in a copying or non-copying manner.
- track (bool, optional) – Should the frame(s) be tracked for notification that ZMQ has finished with it (ignored if copy=True).
Returns: - None (if copy or not track)
- MessageTracker (if track and not copy) – a MessageTracker object, whose pending property will be True until the last send is completed.
-
send_pyobj
(obj, flags=0, protocol=3)¶ send a Python object as a message using pickle to serialize
Parameters:
-
send_string
(u, flags=0, copy=True, encoding='utf-8')¶ send a Python unicode string as a message with an encoding
0MQ communicates with raw bytes, so you must encode/decode text (unicode on py2, str on py3) around 0MQ.
Parameters: - u (Python unicode string (unicode on py2, str on py3)) – The unicode string to send.
- flags (int, optional) – Any valid send flag.
- encoding (str [default: 'utf-8']) – The encoding to be used
-
set
(option, optval)¶ s.set(option, optval)
Set socket options.
See the 0MQ API documentation for details on specific options.
Parameters: - option (int) –
The option to set. Available values will depend on your version of libzmq. Examples include:
zmq.SUBSCRIBE, UNSUBSCRIBE, IDENTITY, HWM, LINGER, FD
- optval (int or bytes) – The value of the option to set.
Notes
Warning
All options other than zmq.SUBSCRIBE, zmq.UNSUBSCRIBE and zmq.LINGER only take effect for subsequent socket bind/connects.
- option (int) –
-
set_hwm
(value)¶ set the High Water Mark
On libzmq ≥ 3, this sets both SNDHWM and RCVHWM
Warning
New values only take effect for subsequent socket bind/connects.
-
set_string
(option, optval, encoding='utf-8')¶ set socket options with a unicode object
This is simply a wrapper for setsockopt to protect from encoding ambiguity.
See the 0MQ documentation for details on specific options.
Parameters:
-
setsockopt
¶ s.set(option, optval)
Set socket options.
See the 0MQ API documentation for details on specific options.
Parameters: - option (int) –
The option to set. Available values will depend on your version of libzmq. Examples include:
zmq.SUBSCRIBE, UNSUBSCRIBE, IDENTITY, HWM, LINGER, FD
- optval (int or bytes) – The value of the option to set.
Notes
Warning
All options other than zmq.SUBSCRIBE, zmq.UNSUBSCRIBE and zmq.LINGER only take effect for subsequent socket bind/connects.
- option (int) –
-
setsockopt_string
(option, optval, encoding='utf-8')¶ set socket options with a unicode object
This is simply a wrapper for setsockopt to protect from encoding ambiguity.
See the 0MQ documentation for details on specific options.
Parameters:
-
classmethod
shadow
(address)¶ Shadow an existing libzmq socket
address is the integer address of the libzmq socket or an FFI pointer to it.
New in version 14.1.
-
subscribe
(topic)¶ Subscribe to a topic
Only for SUB sockets.
New in version 15.3.
-
unbind
(addr)¶ s.unbind(addr)
Unbind from an address (undoes a call to bind).
New in version libzmq-3.2.
New in version 13.0.
Parameters: addr (str) – The address string. This has the form ‘protocol://interface:port’, for example ‘tcp://127.0.0.1:5555’. Protocols supported are tcp, upd, pgm, inproc and ipc. If the address is unicode, it is encoded to utf-8 first.
-
underlying
¶ The address of the underlying libzmq socket
-
unsubscribe
(topic)¶ Unsubscribe from a topic
Only for SUB sockets.
New in version 15.3.
-
Frame
¶
-
class
zmq.
Frame
¶ -
__copy__
()¶ Create a shallow copy of the message.
This does not copy the contents of the Frame, just the pointer. This will increment the 0MQ ref count of the message, but not the ref count of the Python object. That is only done once when the Python is first turned into a 0MQ message.
-
__getattr__
(key)¶ get zmq options by attribute
-
__setattr__
(key, value)¶ set zmq options by attribute
-
buffer
¶ A read-only buffer view of the message contents.
-
bytes
¶ The message content as a Python bytes object.
The first time this property is accessed, a copy of the message contents is made. From then on that same copy of the message is returned.
-
get
(option)¶ Get a Frame option or property.
See the 0MQ API documentation for zmq_msg_get and zmq_msg_gets for details on specific options.
New in version libzmq-3.2.
New in version 13.0.
Changed in version 14.3: add support for zmq_msg_gets (requires libzmq-4.1)
-
set
(option, value)¶ Set a Frame option.
See the 0MQ API documentation for zmq_msg_set for details on specific options.
New in version libzmq-3.2.
New in version 13.0.
-
MessageTracker
¶
-
class
zmq.
MessageTracker
(*towatch)¶ A class for tracking if 0MQ is done using one or more messages.
When you send a 0MQ message, it is not sent immediately. The 0MQ IO thread sends the message at some later time. Often you want to know when 0MQ has actually sent the message though. This is complicated by the fact that a single 0MQ message can be sent multiple times using different sockets. This class allows you to track all of the 0MQ usages of a message.
Parameters: towatch (Event, MessageTracker, Message instances.) – This objects to track. This class can track the low-level Events used by the Message class, other MessageTrackers or actual Messages. -
done
¶ Is 0MQ completely done with the message(s) being tracked?
-
wait
(timeout=-1)¶ mt.wait(timeout=-1)
Wait for 0MQ to be done with the message or until timeout.
Parameters: timeout (float [default: -1, wait forever]) – Maximum time in (s) to wait before raising NotDone. Returns: if done before timeout Return type: None Raises: NotDone
– if timeout reached before I am done.
-
Polling¶
Poller
¶
-
class
zmq.
Poller
¶ A stateful poll interface that mirrors Python’s built-in poll.
-
modify
(socket, flags=3)¶ Modify the flags for an already registered 0MQ socket or native fd.
-
poll
(timeout=None)¶ Poll the registered 0MQ or native fds for I/O.
Parameters: timeout (float, int) – The timeout in milliseconds. If None, no timeout (infinite). This is in milliseconds to be compatible with select.poll()
.Returns: events – The list of events that are ready to be processed. This is a list of tuples of the form (socket, event)
, where the 0MQ Socket or integer fd is the first element, and the poll event mask (POLLIN, POLLOUT) is the second. It is common to callevents = dict(poller.poll())
, which turns the list of tuples into a mapping ofsocket : event
.Return type: list of tuples
-
register
(socket, flags=POLLIN|POLLOUT)¶ p.register(socket, flags=POLLIN|POLLOUT)
Register a 0MQ socket or native fd for I/O monitoring.
register(s,0) is equivalent to unregister(s).
Parameters: - socket (zmq.Socket or native socket) – A zmq.Socket or any Python object having a
fileno()
method that returns a valid file descriptor. - flags (int) – The events to watch for. Can be POLLIN, POLLOUT or POLLIN|POLLOUT. If flags=0, socket will be unregistered.
- socket (zmq.Socket or native socket) – A zmq.Socket or any Python object having a
-
-
zmq.
select
(rlist, wlist, xlist, timeout=None) -> (rlist, wlist, xlist)¶ Return the result of poll as a lists of sockets ready for r/w/exception.
This has the same interface as Python’s built-in
select.select()
function.Parameters: - timeout (float, int, optional) – The timeout in seconds. If None, no timeout (infinite). This is in seconds to be
compatible with
select.select()
. - rlist (list of sockets/FDs) – sockets/FDs to be polled for read events
- wlist (list of sockets/FDs) – sockets/FDs to be polled for write events
- xlist (list of sockets/FDs) – sockets/FDs to be polled for error events
Returns: (rlist, wlist, xlist) – Lists correspond to sockets available for read/write/error events respectively.
Return type: tuple of lists of sockets (length 3)
- timeout (float, int, optional) – The timeout in seconds. If None, no timeout (infinite). This is in seconds to be
compatible with
Exceptions¶
ZMQError
¶
ContextTerminated
¶
-
class
zmq.
ContextTerminated
(errno='ignored', msg='ignored')¶ Wrapper for zmq.ETERM
New in version 13.0.
NotDone
¶
-
class
zmq.
NotDone
¶ Raised when timeout is reached while waiting for 0MQ to finish with a Message
See also
MessageTracker.wait
- object for tracking when ZeroMQ is done
ZMQBindError
¶
-
class
zmq.
ZMQBindError
¶ An error for
Socket.bind_to_random_port()
.See also
Socket.bind_to_random_port
Functions¶
-
zmq.
zmq_version
()¶ return the version of libzmq as a string
-
zmq.
pyzmq_version
()¶ return the version of pyzmq as a string
-
zmq.
zmq_version_info
()¶ Return the version of ZeroMQ itself as a 3-tuple of ints.
-
zmq.
pyzmq_version_info
()¶ return the pyzmq version as a tuple of at least three numbers
If pyzmq is a development version, inf will be appended after the third integer.
-
zmq.
has
()¶ Check for zmq capability by name (e.g. ‘ipc’, ‘curve’)
New in version libzmq-4.1.
New in version 14.1.
-
zmq.
device
(device_type, frontend, backend)¶ Start a zeromq device.
Deprecated since version libzmq-3.2: Use zmq.proxy
Parameters:
-
zmq.
proxy
(frontend, backend, capture)¶ Start a zeromq proxy (replacement for device).
New in version libzmq-3.2.
New in version 13.0.
Parameters:
-
zmq.
curve_keypair
()¶ generate a Z85 keypair for use with zmq.CURVE security
Requires libzmq (≥ 4.0) to have been built with CURVE support.
New in version libzmq-4.0.
New in version 14.0.
Returns: (public, secret) – The public and private keypair as 40 byte z85-encoded bytestrings. Return type: two bytestrings
-
zmq.
get_includes
()¶ Return a list of directories to include for linking against pyzmq with cython.
-
zmq.
get_library_dirs
()¶ Return a list of directories used to link against pyzmq’s bundled libzmq.