py3rosmsgs

1.18.2 verified Sat May 09 auth: no python

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.

pip install py3rosmsgs

Common errors

error ImportError: cannot import name 'Header' from 'std_msgs' ↓

cause Incorrect import path: using `import std_msgs` and then `std_msgs.Header` instead of `from std_msgs.msg import Header`.

fix

Use from std_msgs.msg import Header.

error AttributeError: module 'genpy' has no attribute 'Time' ↓

cause genpy installed but not imported, or an incompatible version of genpy is installed (e.g., Python 2 version).

fix

Ensure genpy is installed: pip install genpy and import it: import genpy. For Python 3, use genpy>=0.6.0.

error ImportError: No module named 'std_msgs' ↓

cause py3rosmsgs not installed or not activated in the environment.

fix

Install py3rosmsgs: pip install py3rosmsgs or source your ROS workspace.

Warnings

breaking 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). ↓

fix Install the version corresponding to your ROS distro. For ROS Noetic, use py3rosmsgs >= 1.18.0.

gotcha 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. ↓

fix Install rospy (usually part of ROS desktop-full) and source your ROS setup.bash before running Python.

deprecated Some message fields may be deprecated in newer ROS versions; check ROS message documentation before relying on specific fields. ↓

fix Refer to ROS wiki for the message specification of your ROS distribution.

Install

pip install py3rosmsgs==1.18.2

Imports

std_msgs.msg.Header
wrong
```
import Header
```
correct
```
from std_msgs.msg import Header
```
Must import from the correct ROS package, not directly. Use the standard ROS import pattern.
geometry_msgs.msg.Pose
wrong
```
from geometry_msgs import Pose
```
correct
```
from geometry_msgs.msg import Pose
```
ROS message classes are under the .msg submodule.

sensor_msgs.msg.Image

wrong

import sensor_msgs.msg.Image as Image

correct

from sensor_msgs.msg import Image

AttributeError if not imported correctly.

genpy
```
import genpy
```
genpy is a dependency that should be automatically installed; no direct import needed for messages.

Quickstart

Basic usage: import common message types and create instances.

from std_msgs.msg import Header
from geometry_msgs.msg import Pose, Point, Quaternion
import genpy
# Create a ROS message
header = Header()
header.stamp = genpy.Time.now()
header.frame_id = 'map'
pose = Pose()
pose.position.x = 1.0
pose.position.y = 2.0
pose.position.z = 0.0
pose.orientation.x = 0.0
pose.orientation.y = 0.0
pose.orientation.z = 0.0
pose.orientation.w = 1.0
print('Header:', header)
print('Pose:', pose)