rosbags.rosbag1 package provides fast read-only access to raw messages stored in the legacy bag format. The rosbag1 support is built for a ROS2 world and some APIs and values perform normalizations to mimic ROS2 behavior and make messages originating from rosbag1 and rosbag2 behave identically. Most notably message types are internally renamed to match their ROS2 counterparts.
Instances of the
Writer class can create and write to new rosbag1 files. It is usually used as a context manager. Before the first message of a topic can be written, its topic must first be added to the bag. The following example shows the typical usage pattern:
from rosbags.rosbag1 import Writer from rosbags.serde import cdr_to_ros1, serialize_cdr from rosbags.typesys.types import std_msgs__msg__String as String # create writer instance and open for writing with Writer('/home/ros/rosbag_2020_03_24.bag') as writer: # add new connection topic = '/chatter' msgtype = String.__msgtype__ connection = writer.add_connection(topic, msgtype, latching=True) # serialize and write message message = String('hello world') timestamp = 42 writer.write(connection, timestamp, cdr_to_ros1(serialize_cdr(message, msgtype), msgtype))
Instances of the
Reader class are typically used as context managers and provide access to bag metadata and contents after the bag has been opened. The following example shows the typical usage pattern:
from rosbags.rosbag1 import Reader from rosbags.serde import deserialize_cdr, ros1_to_cdr # create reader instance with Reader('/home/ros/rosbag_2020_03_24.bag') as reader: # topic and msgtype information is available on .connections list for connection in reader.connections: print(connection.topic, connection.msgtype) # iterate over messages for connection, timestamp, rawdata in reader.messages(): if connection.topic == '/imu_raw/Imu': msg = deserialize_cdr(ros1_to_cdr(rawdata, connection.msgtype), connection.msgtype) print(msg.header.frame_id) # messages() accepts connection filters connections = [x for x in reader.connections if x.topic == '/imu_raw/Imu'] for connection, timestamp, rawdata in reader.messages(connections=connections): msg = deserialize_cdr(ros1_to_cdr(rawdata, connection.msgtype), connection.msgtype) print(msg.header.frame_id)