https://cyber-rt.readthedocs.io/en/latest/CyberRT_Python_API.html
https://cyber-rt.readthedocs.io/en/latest/api/pythonapi.html

1. 背景

Cyber RT 核心代码是由 C++ 开发，同时为了方便开发者，提供了 Python 接口。

2. Cyber RT Python 接口实现思路

Cyber RT Python 接口的实现思路是在 Cyber RT C++ 实现的基础上，做了一层 Python 的封装，由 Python 来调用 C++ 的实现函数。Cyber RT 中 Python Wrapper 的实现没有使用 swig 等第三方工具，完全自主实现，以此保证代码的高可维护性和可读性。

3. 主要接口

目前提供的主要接口包括：

channel 读、写
server/client 通信
record 信息查询
record 文件读、写
Time/Duration/Rate 时间操作
Timer 定时器

3.1 Channel 读写接口

使用步骤是：

首先创建 Node;
创建对应的 reader 或 writer；
如果是向 channel 写数据，调用 writer 的 write 接口；
如果是从 channel 读数据，调用 node 的 spin，并在回调函数 callback 中对消息进行处理；

接口定义如下：

class Node:"""Class for Cyber RT Node wrapper."""def create_writer(self, name, data_type, qos_depth=1):"""create a topic writer for send message to topic.@param self@param name str: topic name@param data_type proto: message class for serialization"""def create_reader(self, name, data_type, callback, args=None):"""create a topic reader for receive message from topic.@param self@param name str: topic name@param data_type proto: message class for serialization@callback fn: function to call (fn(data)) when data isreceived. If args is set, the function mustaccept the args as a second argument,i.e. fn(data, args)@args any: additional arguments to pass to the callback"""def create_client(self, name, request_data_type, response_data_type):""""""def create_service(self, name, req_data_type, res_data_type, callback, args=None):def spin(self):"""spin in wait and process message.@param self"""class Writer(object):"""Class for Cyber RT writer wrapper."""def write(self, data):"""writer msg string"""

3.2 Record 接口

Record 读的操作是：

创建一个 RecordReader;
对 Record 进行迭代读；

Record 写的操作是：

创建一个 RecordReader;
对 Record 进行写消息；

接口定义如下：

class RecordReader(object):"""Class for Cyber RT RecordReader wrapper."""def read_messages(self, start_time=0, end_time=18446744073709551615):"""read message from bag file.@param self@param start_time:@param end_time:@return: generator of (message, data_type, timestamp)"""def get_messagenumber(self, channel_name):"""return message count."""def get_messagetype(self, channel_name):"""return message type."""def get_protodesc(self, channel_name):"""return message protodesc."""def get_headerstring(self):"""return message header string."""def reset(self):"""return reset."""return _Cyber_RECORD.PyRecordReader_Reset(self.record_reader)def get_channellist(self):"""return channel list."""return _Cyber_RECORD.PyRecordReader_GetChannelList(self.record_reader)class RecordWriter(object):"""Class for Cyber RT RecordWriter wrapper."""def open(self, path):"""open record file for write."""def write_channel(self, channel_name, type_name, proto_desc):"""writer channel by channelname,typename,protodesc"""def write_message(self, channel_name, data, time, raw = True):"""writer msg:channelname,data,time,is data raw"""def set_size_fileseg(self, size_kilobytes):"""return filesegment size."""def set_intervaltime_fileseg(self, time_sec):"""return file interval time."""def get_messagenumber(self, channel_name):"""return message count."""def get_messagetype(self, channel_name):"""return message type."""def get_protodesc(self, channel_name):"""return message protodesc."""

3.3 Time 接口

class Time(object):@staticmethoddef now():time_now = Time(_CYBER_TIME.PyTime_now())return time_now@staticmethoddef mono_time():mono_time = Time(_CYBER_TIME.PyTime_mono_time())return mono_timedef to_sec(self):return _CYBER_TIME.PyTime_to_sec(self.time)def to_nsec(self):return _CYBER_TIME.PyTime_to_nsec(self.time)def sleep_until(self, nanoseconds):return _CYBER_TIME.PyTime_sleep_until(self.time, nanoseconds)

3.4 Timer 接口


class Timer(object):def set_option(self, period, callback, oneshot=0):'''period The period of the timer, unit is mscallback The tasks that the timer needs to performoneshot 1: perform the callback only after the first timing cycle0:perform the callback every timed period'''def start(self):def stop(self):

4. 例子

4.1 读 channel （参见 cyber/python/cyber_py3/examples/listener.py)

"""Module for example of listener."""
from cyber.python.cyber_py3 import cyber
from cyber.proto.unit_test_pb2 import ChatterBenchmarkdef callback(data):"""Reader message callback."""print("=" * 80)print("py:reader callback msg->:")print(data)print("=" * 80)def test_listener_class():"""Reader message."""print("=" * 120)test_node = cyber.Node("listener")test_node.create_reader("channel/chatter", ChatterBenchmark, callback)test_node.spin()if __name__ == '__main__':cyber.init()test_listener_class()cyber.shutdown()

在 apollo 镜像中执行命令

export PYTHONPATH=/apollo/bazel-bin/cyber/python/internal:/apollo:/apollo/cyber/proto

在 /apollo/cyber 目录下执行

python -m grpc_tools.protoc -I=./proto --python_out=./proto --grpc_python_out=./proto  ./proto/unit_test.proto

用于生成以下两个文件 unit_test_pb2.py 和 unit_test_pb2_grpc.py。

4.2 写 channel（参见 cyber/python/cyber_py3/examples/talker.py)

"""Module for example of talker."""
import timefrom cyber.python.cyber_py3 import cyber
from cyber.proto.unit_test_pb2 import ChatterBenchmarkdef test_talker_class():"""Test talker."""msg = ChatterBenchmark()msg.content = "py:talker:send Alex!"msg.stamp = 9999msg.seq = 0print(msg)test_node = cyber.Node("node_name1")g_count = 1writer = test_node.create_writer("channel/chatter", ChatterBenchmark, 6)while not cyber.is_shutdown():time.sleep(1)g_count = g_count + 1msg.seq = g_countmsg.content = "I am python talker."print("=" * 80)print("write msg -> %s" % msg)writer.write(msg)if __name__ == '__main__':cyber.init("talker_sample")test_talker_class()cyber.shutdown()

分别执行

python cyber/python/cyber_py3/examples/listener.py

和

python cyber/python/cyber_py3/examples/talker.py

listener.py 打印如下：

========================================================================================================================
================================================================================
py:reader callback msg->:
stamp: 9999
seq: 2
content: "I am python talker."================================================================================
================================================================================
py:reader callback msg->:
stamp: 9999
seq: 3
content: "I am python talker."================================================================================

talker.py 打印如下：

stamp: 9999
seq: 0
content: "py:talker:send Alex!"================================================================================
write msg -> stamp: 9999
seq: 2
content: "I am python talker."================================================================================
write msg -> stamp: 9999
seq: 3
content: "I am python talker."================================================================================

4.3 读写消息到 Record 文件（参见 cyber/python/cyber_py3/examples/record.py)

"""
Module for example of record.
Run with:bazel run //cyber/python/cyber_py3/examples:record
"""import timefrom google.protobuf.descriptor_pb2 import FileDescriptorProtofrom cyber.proto.unit_test_pb2 import Chatter
from cyber.python.cyber_py3 import record
from modules.common.util.testdata.simple_pb2 import SimpleMessageMSG_TYPE = "apollo.common.util.test.SimpleMessage"
MSG_TYPE_CHATTER = "apollo.cyber.proto.Chatter"def test_record_writer(writer_path):"""Record writer."""fwriter = record.RecordWriter()fwriter.set_size_fileseg(0)fwriter.set_intervaltime_fileseg(0)if not fwriter.open(writer_path):print('Failed to open record writer!')returnprint('+++ Begin to writer +++')# Writer 2 SimpleMessagemsg = SimpleMessage()msg.text = "AAAAAA"file_desc = msg.DESCRIPTOR.fileproto = FileDescriptorProto()file_desc.CopyToProto(proto)proto.name = file_desc.namedesc_str = proto.SerializeToString()print(msg.DESCRIPTOR.full_name)fwriter.write_channel('simplemsg_channel', msg.DESCRIPTOR.full_name, desc_str)fwriter.write_message('simplemsg_channel', msg, 990, False)fwriter.write_message('simplemsg_channel', msg.SerializeToString(), 991)# Writer 2 Chattermsg = Chatter()msg.timestamp = 99999msg.lidar_timestamp = 100msg.seq = 1file_desc = msg.DESCRIPTOR.fileproto = FileDescriptorProto()file_desc.CopyToProto(proto)proto.name = file_desc.namedesc_str = proto.SerializeToString()print(msg.DESCRIPTOR.full_name)fwriter.write_channel('chatter_a', msg.DESCRIPTOR.full_name, desc_str)fwriter.write_message('chatter_a', msg, 992, False)msg.seq = 2fwriter.write_message("chatter_a", msg.SerializeToString(), 993)fwriter.close()def test_record_reader(reader_path):"""Record reader."""freader = record.RecordReader(reader_path)time.sleep(1)print('+' * 80)print('+++ Begin to read +++')count = 0for channel_name, msg, datatype, timestamp in freader.read_messages():count += 1print('=' * 80)print('read [%d] messages' % count)print('channel_name -> %s' % channel_name)print('msgtime -> %d' % timestamp)print('msgnum -> %d' % freader.get_messagenumber(channel_name))print('msgtype -> %s' % datatype)print('message is -> %s' % msg)print('***After parse(if needed),the message is ->')if datatype == MSG_TYPE:msg_new = SimpleMessage()msg_new.ParseFromString(msg)print(msg_new)elif datatype == MSG_TYPE_CHATTER:msg_new = Chatter()msg_new.ParseFromString(msg)print(msg_new)if __name__ == '__main__':test_record_file = "/tmp/test_writer.record"print('Begin to write record file: {}'.format(test_record_file))test_record_writer(test_record_file)print('Begin to read record file: {}'.format(test_record_file))test_record_reader(test_record_file)

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