erer¶
1. Background¶
The core functions of Cyber RT are developed in C++. We also provide more python interfaces to help developers build their own utilities for specific projects.
2. Cyber RT Python Interfaces¶
The python interfaces of Cyber RT are wrapper the corresponding C++ interfaces. The implementation doesn’t rely on other third-party tools, e.g. swig, which makes it easier to maintain.
3. Overview of Python Interfaces in Cyber RT¶
So far, the python interfaces covers:
access the information of channels
server/client communication
query informatoin in record files
read and write from/to record files
Time/Duration/Rate related operations
Timer
3.1 Read/Write of Channels¶
Steps shown as below:
First create a Node；
Create corresponding reader or writer;
If write to a channel, use write interface in writer.
If read from a channel, use the spin interface in the node, and process the messages in your callback function
The interfaces are shown below:
class Node:
"""
Class for cyber 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 is
received. If args is set, the function must
accept 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 writer wrapper.
"""
def write(self, data):
"""
writer msg string
"""
3.2 Record Interfaces¶
Read from record：
Create a RecordReader;
Read messages from Record;
Write to record：
Create a RecordWriter
Write messages to record；
The interfaces are shown below:
class RecordReader(object):
"""
Class for cyber 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 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 Interfaces¶
class Time(object):
@staticmethod
def now():
time_now = Time(_CYBER_TIME.PyTime_now())
return time_now
@staticmethod
def mono_time():
mono_time = Time(_CYBER_TIME.PyTime_mono_time())
return mono_time
def 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 Interfaces¶
class Timer(object):
def set_option(self, period, callback, oneshot=0):
"""
set the option of timer.
@param period The period of the timer, unit is ms.
@param callback The tasks that the timer needs to perform.
@param oneshot 1:perform the callback only after the first timing cycle
0:perform the callback every timed period
"""
def start(self):
def stop(self):
4. Examples¶
4.1 Read from Channel (in cyber/python/cyber_py3/examples/listener.py)¶
from cyber_py3 import cyber
from cyber.proto.unit_test_pb2 import ChatterBenchmark
def 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()
4.2 Write to Channel(in cyber/python/cyber_py3/examples/talker.py)¶
import time
from cyber_py3 import cyber
from cyber.proto.unit_test_pb2 import ChatterBenchmark
def test_talker_class():
"""
Test talker.
"""
msg = ChatterBenchmark()
msg.content = "py:talker:send Alex!"
msg.stamp = 9999
msg.seq = 0
print(msg)
test_node = cyber.Node("node_name1")
g_count = 1
writer = test_node.create_writer("channel/chatter", ChatterBenchmark, 6)
while not cyber.is_shutdown():
time.sleep(1)
g_count = g_count + 1
msg.seq = g_count
msg.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()
4.3 Read and Write Messages from/to Record File(in cyber/python/cyber_py3/examples/record.py)¶
"""
Module for example of record.
Run with:
bazel run //cyber/python/cyber_py3/examples:record
"""
import time
from google.protobuf.descriptor_pb2 import FileDescriptorProto
from cyber.proto.unit_test_pb2 import Chatter
from cyber.python.cyber_py3 import record
from modules.common.util.testdata.simple_pb2 import SimpleMessage
MSG_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!')
return
print('+++ Begin to writer +++')
# Writer 2 SimpleMessage
msg = SimpleMessage()
msg.text = "AAAAAA"
file_desc = msg.DESCRIPTOR.file
proto = FileDescriptorProto()
file_desc.CopyToProto(proto)
proto.name = file_desc.name
desc_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 Chatter
msg = Chatter()
msg.timestamp = 99999
msg.lidar_timestamp = 100
msg.seq = 1
file_desc = msg.DESCRIPTOR.file
proto = FileDescriptorProto()
file_desc.CopyToProto(proto)
proto.name = file_desc.name
desc_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 = 2
fwriter.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 = 0
for channel_name, msg, datatype, timestamp in freader.read_messages():
count += 1
print('=' * 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)