{"id":28075,"library":"py3rosmsgs","title":"py3rosmsgs","description":"Port of ROS 1.0 messages to Python 3, providing pre-compiled message definitions for common ROS packages (std_msgs, geometry_msgs, sensor_msgs, etc.). Version 1.18.2 is current; release cadence is tied to ROS releases. The library is a Python 3 runtime dependency for ROS1 nodes when using Python 3, and includes generated Python classes from ROS message definitions.","status":"active","version":"1.18.2","language":"python","source_language":"en","source_url":"https://github.com/ros/genpy","tags":["ros","robotics","messages","python3"],"install":[{"cmd":"pip install py3rosmsgs","lang":"bash","label":"Install from PyPI"},{"cmd":"pip install py3rosmsgs==1.18.2","lang":"bash","label":"Pin version"}],"dependencies":[],"imports":[{"note":"Must import from the correct ROS package, not directly. Use the standard ROS import pattern.","wrong":"import Header","symbol":"std_msgs.msg.Header","correct":"from std_msgs.msg import Header"},{"note":"ROS message classes are under the .msg submodule.","wrong":"from geometry_msgs import Pose","symbol":"geometry_msgs.msg.Pose","correct":"from geometry_msgs.msg import Pose"},{"note":"AttributeError if not imported correctly.","wrong":"import sensor_msgs.msg.Image as Image","symbol":"sensor_msgs.msg.Image","correct":"from sensor_msgs.msg import Image"},{"note":"genpy is a dependency that should be automatically installed; no direct import needed for messages.","wrong":"","symbol":"genpy","correct":"import genpy"}],"quickstart":{"code":"from std_msgs.msg import Header\nfrom geometry_msgs.msg import Pose, Point, Quaternion\nimport genpy\n# Create a ROS message\nheader = Header()\nheader.stamp = genpy.Time.now()\nheader.frame_id = 'map'\npose = Pose()\npose.position.x = 1.0\npose.position.y = 2.0\npose.position.z = 0.0\npose.orientation.x = 0.0\npose.orientation.y = 0.0\npose.orientation.z = 0.0\npose.orientation.w = 1.0\nprint('Header:', header)\nprint('Pose:', pose)","lang":"python","description":"Basic usage: import common message types and create instances."},"warnings":[{"fix":"Install the version corresponding to your ROS distro. For ROS Noetic, use py3rosmsgs >= 1.18.0.","message":"py3rosmsgs expects a specific ROS distribution; version mismatch can cause missing messages or incorrect field definitions. Ensure the installed version matches the ROS distribution (e.g., Melodic, Noetic).","severity":"breaking","affected_versions":"all"},{"fix":"Install rospy (usually part of ROS desktop-full) and source your ROS setup.bash before running Python.","message":"py3rosmsgs only provides message definitions; you still need rospy and a full ROS environment to publish/subscribe. Importing messages without rospy will not enable communication.","severity":"gotcha","affected_versions":"all"},{"fix":"Refer to ROS wiki for the message specification of your ROS distribution.","message":"Some message fields may be deprecated in newer ROS versions; check ROS message documentation before relying on specific fields.","severity":"deprecated","affected_versions":">=1.18.0"}],"env_vars":null,"last_verified":"2026-05-09T00:00:00.000Z","next_check":"2026-08-07T00:00:00.000Z","problems":[{"fix":"Use `from std_msgs.msg import Header`.","cause":"Incorrect import path: using `import std_msgs` and then `std_msgs.Header` instead of `from std_msgs.msg import Header`.","error":"ImportError: cannot import name 'Header' from 'std_msgs'"},{"fix":"Ensure genpy is installed: `pip install genpy` and import it: `import genpy`. For Python 3, use genpy>=0.6.0.","cause":"genpy installed but not imported, or an incompatible version of genpy is installed (e.g., Python 2 version).","error":"AttributeError: module 'genpy' has no attribute 'Time'"},{"fix":"Install py3rosmsgs: `pip install py3rosmsgs` or source your ROS workspace.","cause":"py3rosmsgs not installed or not activated in the environment.","error":"ImportError: No module named 'std_msgs'"}],"ecosystem":"pypi","meta_description":null,"install_score":null,"install_tag":null,"quickstart_score":null,"quickstart_tag":null}