server.py 文件源码

def install_missing_requirements(module):
    """
    Some of the modules require external packages to be installed. This gets
    the list from the `REQUIREMENTS` module attribute and attempts to
    install the requirements using pip.
    :param module: GPIO module
    :type module: ModuleType
    :return: None
    :rtype: NoneType
    """
    reqs = getattr(module, "REQUIREMENTS", [])
    if not reqs:
        _LOG.info("Module %r has no extra requirements to install." % module)
        return
    import pkg_resources
    pkgs_installed = pkg_resources.WorkingSet()
    pkgs_required = []
    for req in reqs:
        if pkgs_installed.find(pkg_resources.Requirement.parse(req)) is None:
            pkgs_required.append(req)
    if pkgs_required:
        from pip.commands.install import InstallCommand
        from pip.status_codes import SUCCESS
        cmd = InstallCommand()
        result = cmd.main(pkgs_required)
        if result != SUCCESS:
            raise CannotInstallModuleRequirements(
                "Unable to install packages for module %r (%s)..." % (
                    module, pkgs_required))