ament_virtualenv

Python virtual environment wrapper package, based on catkin_virtualenv.

This package provides a mechanism to:

• choose that the target package should be run in a virtual Python environment of the desired version
• export python library requirements in requirements.txt format via package.xml.
• bundle a virtualenv within a ament package, inheriting requirements from any dependencies.
• wrap python scripts and tests in a ament package with a virtualenv loader.

At build time, Python commands and CMake macros provided by this package will create a virtualenv, and create wrapper scripts for Python scripts installed by the in the target package. Both will be included in the release.

This library is GPL licensed due to the inclusion of dh_virtualenv.

Exporting python requirements

The package containing python modules with external library dependencies should define a requirements.txt:

GitPython>=2.1.5
psutil>=5.2.2
wrapt>=1.10.10

Add an export to package.xml:

<export>
  <pip_requirements>requirements.txt</pip_requirements>
</export>

If your package uses ament_python as build tool, add the following to your setup.py file:

import setuptools.command.install
import ament_virtualenv.install

class InstallCommand(setuptools.command.install.install):
    def run(self):
        super().run()
        ament_virtualenv.install.install_venv(
            install_base=self.install_base,
            package_name=package_name,
            python_version='2'
        )
        # instead of self.install_base we may also use:
        # self.config_vars['platbase'] or self.config_vars['base']
        # Exchange the python_version with '3' if your package uses Python3.
        return

setup(
    cmdclass={
        'install': InstallCommand
    },

If your package uses ament_cmake as build tool, add the following to your CMakeLists.txt:

find_package(ament_cmake_virtualenv REQUIRED)
ament_generate_virtualenv(PYTHON_VERSION 2)
# Exchange the python_version with '3' if your package uses Python3.

# Tell ament to install your Python module:
ament_python_install_module(path/to/my/module.py)
# ... or a whole folder containing a Python package:
ament_python_install_package(path/to/your/package)

# Tell ament also to copy the requirements.txt file
install(FILES requirements.txt
  DESTINATION ${CMAKE_INSTALL_PREFIX}/share/${PROJECT_NAME})

Finally, add an build dependency on ament_virtualenv to your package.xml.

If you're using ament_python as build tool:

<build_depend>ament_virtualenv</build_depend>

If you're using ament_cmake as build tool:

<build_depend>ament_cmake_virtualenv</build_depend>

If an ament package exports dependencies in a requirements.txt file, any dependent ament package that bundles a virtualenv (see below) will inherit those dependencies. Note that the requirements installation does not do any dependency resolution - similar to how pip operates, the topmost dependency declaration 'wins' (pypa/pip#988).

Additional CMake Options

The following options are supported by ament_generate_virtualenv():

ament_generate_virtualenv(
  # Select an alternative version of the python interpreter - it must be installed on the system. Minor version is optional.
  PYTHON_VERSION 3.7  # Default 3

  # Choose not to use underlying system packages. This excludes any python packages installed by apt or system-pip from the environment.
  USE_SYSTEM_PACKAGES FALSE  # Default TRUE

  # Disable including pip requirements from catkin dependencies of this package.
  ISOLATE_REQUIREMENTS TRUE  # Default FALSE

  # Provide extra arguments to the underlying pip invocation
  EXTRA_PIP_ARGS
    --no-binary=:all:
    -vvv
)