Find the python packages on which a ros package depends on

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There's a few ways to get a list of packages a ROS package depends on, but you may have to do some more work to figure out if they're a Python package.

If you just want to check first level dependencies online, you can look at the dependencies tab for the package on index.ros.org.

https://index.ros.org/p/rospack/#noet...

If the ROS package is installable via apt, you can use apt depends ros-noetic-pkgname to get the first level of dependencies:

$ ros-noetic-rospack
  Depends: libboost-filesystem1.71.0
  Depends: libboost-program-options1.71.0
  Depends: libc6 (>= 2.14)
  Depends: libgcc-s1 (>= 3.0)
  Depends: libpython3.8 (>= 3.8.2)
  Depends: libstdc++6 (>= 5.2)
  Depends: libtinyxml2-6a (>= 5.0.0)
  Depends: libboost-filesystem-dev
  Depends: libboost-program-options-dev
  Depends: libboost-system-dev
  Depends: libtinyxml2-dev
  Depends: pkg-config
    pkgconf
  Depends: python3-catkin-pkg-modules
  Depends: python3-dev
  Depends: python3-rosdep-modules
  Depends: ros-noetic-ros-environment

If you want to find all dependencies of it's dependencies, you can use the --recurse option

$ apt depends --recurse --no-recommends --no-suggests --no-conflicts --no-breaks --no-replaces --no-enhances ros-noetic-rospack
... lots of output ...

If you want to find all dependencies that depend on Python or Python 3, you can use py3-ready with the --target and --dot options, and then visualize that with graphviz.

py3-ready check-apt --dot --target python3 ros-noetic-rospack

That can work with packages in a sourced catkin workspace too

py3-ready check-package --dot --target python3 my_ros_package