{"id":5818,"library":"rosbags","title":"Rosbags","description":"Rosbags is a pure Python library designed to read, modify, convert, and write rosbag files for both ROS 1 and ROS 2. It offers high-level interfaces, support for various rosbag formats (rosbag1 and rosbag2), an extensible type system with serializers and deserializers, and efficient conversion capabilities. The library is actively maintained with regular releases. The current version is 0.11.0.","status":"active","version":"0.11.0","language":"en","source_language":"en","source_url":"https://github.com/ternaris/rosbags","tags":["ros","rosbag","ros1","ros2","robotics","data-logging","serialization","deserialization","converter","mcap","cdr"],"install":[{"cmd":"pip install rosbags","lang":"bash","label":"Install latest version"}],"dependencies":[{"reason":"Requires Python 3.10 or newer.","package":"python","optional":false},{"reason":"Used for numerical data types and operations.","package":"numpy","optional":false},{"reason":"Used for YAML parsing, especially for metadata files.","package":"ruamel-yaml","optional":false},{"reason":"Optional dependency for LZ4 compression, used for Python < 3.14.","package":"lz4","optional":true},{"reason":"Optional dependency for LZ4 compression, used for Python >= 3.14.","package":"safelz4","optional":true},{"reason":"Optional dependency for Zstandard compression.","package":"zstandard","optional":true},{"reason":"Required for type hints, version >=4.5.","package":"typing-extensions","optional":false}],"imports":[{"note":"Primary high-level interface for reading rosbag files.","symbol":"AnyReader","correct":"from rosbags.highlevel import AnyReader"},{"note":"Used to access predefined message type stores (e.g., ROS2_FOXY).","symbol":"Stores","correct":"from rosbags.typesys import Stores"},{"note":"Function to retrieve a message type store.","symbol":"get_typestore","correct":"from rosbags.typesys import get_typestore"},{"note":"Specific reader for ROS2 bag files when high-level AnyReader is not sufficient.","symbol":"Reader","correct":"from rosbags.rosbag2 import Reader"},{"note":"The import path for Serde-related modules changed. Direct import from `rosbags.serde` is now preferred. Older paths like `rosbags.serde.serdes` were deprecated around version 0.9.20.","wrong":"from rosbags.serde.serdes import Serde","symbol":"Serde","correct":"from rosbags.serde import Serde"}],"quickstart":{"code":"from pathlib import Path\nfrom rosbags.highlevel import AnyReader\nfrom rosbags.typesys import Stores, get_typestore\n\n# Replace with the actual path to your rosbag file/directory\n# For testing, you can create a dummy bag file or use an existing one.\n# Example: bagpath = Path('./path/to/my_rosbag')\n# Ensure the path points to the directory containing a ROS2 bag or a ROS1 .bag file.\nbagpath = Path('test_rosbag_dir') # Placeholder, modify as needed\n\n# Create a type store to use if the bag has no message definitions or for custom types.\n# ROS2_FOXY is an example; choose the appropriate ROS distribution if needed.\ntypestore = get_typestore(Stores.ROS2_FOXY)\n\ntry:\n    # Create reader instance and open for reading.\n    with AnyReader([bagpath], default_typestore=typestore) as reader:\n        # Filter connections (topics) if desired. Here, we read all messages.\n        # connections = [x for x in reader.connections if x.topic == '/imu_raw/Imu']\n        \n        print(f\"Found {len(reader.connections)} connections (topics) in the bag.\")\n        for connection in reader.connections:\n            print(f\"  Topic: {connection.topic}, Type: {connection.msgtype}\")\n\n        message_count = 0\n        for connection, timestamp, rawdata in reader.messages():\n            # Deserialize the message data\n            msg = reader.deserialize(rawdata, connection.msgtype)\n            # Access message fields (example for a common message type)\n            # This assumes your message type has a 'header' and 'frame_id'\n            # Adapt based on the actual message types in your bag.\n            try:\n                if hasattr(msg, 'header') and hasattr(msg.header, 'frame_id'):\n                    print(f\"[{timestamp}] Topic: {connection.topic}, Frame ID: {msg.header.frame_id}\")\n                else:\n                    print(f\"[{timestamp}] Topic: {connection.topic}, Message: {msg}\")\n            except AttributeError:\n                print(f\"[{timestamp}] Topic: {connection.topic}, Message: {msg}\") # Fallback for messages without header\n            message_count += 1\n            if message_count >= 10: # Limit output for brevity\n                print(\"... (truncated after 10 messages)\")\n                break\nexcept FileNotFoundError:\n    print(f\"Error: Bag file or directory not found at {bagpath}. Please create or specify a valid path.\")\nexcept Exception as e:\n    print(f\"An error occurred: {e}\")\n","lang":"python","description":"This quickstart demonstrates how to open a rosbag file (ROS1 or ROS2), iterate through its messages, and deserialize them using the high-level `AnyReader` interface. It includes explicit handling for type stores, which is crucial for correct message deserialization, especially if the bag does not contain complete message definitions or for custom message types. Remember to replace `test_rosbag_dir` with the actual path to your rosbag."},"warnings":[{"fix":"Update your imports to the new structure, typically importing directly from `rosbags.serde` or using the high-level `AnyReader` and its `deserialize` method which handles these internally. The official documentation's quickstart demonstrates the recommended approach using `rosbags.highlevel` and `rosbags.typesys`.","message":"The import paths for serialization/deserialization modules were refactored, specifically affecting imports from `rosbags.serde.serdes`. Code relying on these old paths will break.","severity":"breaking","affected_versions":">=0.9.20 (released 2024-02-29)"},{"fix":"Always provide a `default_typestore` (e.g., `get_typestore(Stores.ROS2_FOXY)`) to `AnyReader` or `Reader` instances. For custom message types, ensure they are registered with the `Typestore` or included in a custom message definition path.","message":"When reading rosbag files, especially those without embedded message definitions or containing custom message types, `rosbags` requires an explicit `Typestore` to correctly deserialize messages. Failing to provide an appropriate `default_typestore` can lead to deserialization errors or incorrect message interpretation.","severity":"gotcha","affected_versions":"All versions"},{"fix":"Utilize the iterator-based approach (e.g., `reader.messages()`) to process messages one by one rather than loading all messages at once. Filter connections using `reader.connections` to only process relevant topics. Ensure your processing logic within the loop is memory-efficient.","message":"While `rosbags` itself is designed for efficient handling of bag files, processing extremely large rosbag files (e.g., hundreds of GBs or millions of messages) without care can still lead to high memory consumption, especially if users attempt to load all messages or connections into memory simultaneously. Iterators are provided for a reason.","severity":"gotcha","affected_versions":"All versions"}],"env_vars":null,"last_verified":"2026-04-14T00:00:00.000Z","next_check":"2026-07-13T00:00:00.000Z"}