rosbags.rosbag2

Rosbags support for rosbag2 files.

Readers and writers provide access to metadata and raw message content saved in the rosbag2 format.

class rosbags.rosbag2.Reader(path)

Bases: object

Reader for rosbag2 files.

It implements all necessary features to access metadata and message streams.

Version history:

  • Version 1: Initial format.

  • Version 2: Changed field sizes in C++ implementation.

  • Version 3: Added compression.

  • Version 4: Added QoS metadata to topics, changed relative file paths.

  • Version 5: Added per file metadata.

  • Version 6: Added custom_data dict to metadata.

  • Version 7: Added type_description_hash to topic metadata.

  • Version 8: Added ros_distro to metadata.

  • Version 9: Changed QoS metadata serialization and enums.

Parameters:

path (Path | str)

close()

Close rosbag2.

Return type:

None

property compression_format: str | None

Compression format.

property compression_mode: str | None

Compression mode.

property duration: int

Duration in nanoseconds between earliest and latest messages.

property end_time: int

Timestamp in nanoseconds after the latest message.

property message_count: int

Total message count.

messages(connections=(), start=None, stop=None)

Read messages from bag.

Parameters:

  • connections (Iterable[Connection]) – Iterable with connections to filter for. An empty iterable disables filtering on connections.

  • start (int | None) – Yield only messages at or after this timestamp (ns).

  • stop (int | None) – Yield only messages before this timestamp (ns).

Yields:

tuples of connection, timestamp (ns), and rawdata.

Raises:

ReaderError – If reader was not opened.

Return type:

Generator[tuple[Connection, int, bytes], None, None]

open()

Open rosbag2.

Return type:

None

property ros_distro: str | None

ROS distribution.

property start_time: int

Timestamp in nanoseconds of the earliest message.

property topics: dict[str, TopicInfo]

Topic information.

exception rosbags.rosbag2.ReaderError

Bases: Exception

Reader Error.

class rosbags.rosbag2.Writer(path, *, version=None)

Bases: object

Rosbag2 writer.

This class implements writing of rosbag2 files in version 8. It should be used as a contextmanager.

Parameters:

  • path (Path | str)

  • version (Literal[8, 9] | None)

class CompressionFormat(value, names=<not given>, *values, module=None, qualname=None, type=None, start=1, boundary=None)

Bases: IntEnum

Compession formats.

class CompressionMode(value, names=<not given>, *values, module=None, qualname=None, type=None, start=1, boundary=None)

Bases: IntEnum

Compession modes.

add_connection(topic, msgtype, *, typestore=None, msgdef=None, rihs01=None, serialization_format='cdr', offered_qos_profiles=())

Add a connection.

This function can only be called after opening a bag.

Parameters:

  • topic (str) – Topic name.

  • msgtype (str) – Message type.

  • typestore (Typestore | None) – Typestore.

  • msgdef (str | None) – Message definiton.

  • rihs01 (str | None) – Message hash.

  • serialization_format (str) – Serialization format.

  • offered_qos_profiles (Sequence[Qos] | str) – QOS Profile.

Return type:

Connection

Returns:

Connection object.

Raises:

WriterError – Bag not open or topic previously registered.

close()

Close rosbag2 after writing.

Closes open database transactions and writes metadata.yaml.

Return type:

None

open()

Open rosbag2 for writing.

Create base directory and open database connection.

Return type:

None

set_compression(mode, fmt)

Enable compression on bag.

This function has to be called before opening.

Parameters:

  • mode (CompressionMode) – Compression mode to use, either ‘file’ or ‘message’.

  • fmt (CompressionFormat) – Compressor to use, currently only ‘zstd’.

Raises:

WriterError – Bag already open.

Return type:

None

set_custom_data(key, value)

Set key value pair in custom_data.

Parameters:

  • key (str) – Key to set.

  • value (str) – Value to set.

Raises:

WriterError – If value has incorrect type.

Return type:

None

write(connection, timestamp, data)

Write message to rosbag2.

Parameters:

  • connection (Connection) – Connection to write message to.

  • timestamp (int) – Message timestamp (ns).

  • data (bytes | memoryview) – Serialized message data.

Raises:

WriterError – Bag not open or topic not registered.

Return type:

None

exception rosbags.rosbag2.WriterError

Bases: Exception

Writer Error.