python3中import tf报错，记录，ubuntu18.04环境，树莓派。
1、编辑.bashrc文件，注释
# source ~/你的workspace/devel/setup.bash
2、安装catkin build
sudo apt-get install python-catkin-tools
3、创建一个新的仓库，并做好配置，arm板/usr/lib/aarch64-linux-gnu/libpython3.6m.so，x86板/usr/lib/x86_64-linux-gnu/libpython3.6m.so
mkdir ~/secondary_build_ws && cd ~/secondary_build_ws && catkin config -DPYTHON_EXECUTABLE=/usr/bin/python3 -DPYTHON_INCLUDE_DIR=/usr/include/python3.6m -DPYTHON_LIBRARY=/usr/lib/aarch64-linux-gnu/libpython3.6m.so && catkin config --install
4、clone仓库geometry2
mkdir src && cd src && git clone -b melodic-devel https://github.com/ros/geometry2
5、编译
cd ..
catkin build
如果编译时报错No module named em，则需要安装empy：
pip install empy pip3 install empy
6、编译完成后一定执行下，否则报ImportError: dynamic module does not define module export function (PyInit__tf2）
source ~/secondary_build_ws/devel/setup.bash --extend
就OK了。
最后添加到.bashrc中，一定要注意顺序：
source /opt/ros/melodic/setup.bash source ~/你的workspace/devel/setup.bash source ~/secondary_build_ws/devel/setup.bash --extend export PYTHONPATH=~/secondary_build_ws/devel/lib/python3/dist-packages:$PYTHONPATH
文章参考地址：https://zhuanlan.zhihu.com/p/578530492