Source code for vmware.vapi.lib.load

"""
Convenience methods for dynamic loading
"""

__author__ = 'VMware, Inc.'
__copyright__ = 'Copyright 2011-2014 VMware, Inc.  All rights reserved. -- VMware Confidential'

import logging
import six

from vmware.vapi.settings import config

logger = logging.getLogger(__name__)


def dynamic_import(constructor):
    """
    Dynamically import a module and get the specified module attribute

    :type    constructor: :class:`str`
    :param   constructor: Fully qualified module attribute
    :rtype:  :class:`object`
    :return: Python object
    """
    target_attr = None
    if constructor:
        if isinstance(constructor, six.string_types):
            try:
                module_name, fn = constructor.rsplit('.', 1)
                module = __import__(module_name, globals(), locals(), [fn])
                target_attr = getattr(module, fn)
            except ImportError as err:
                logger.exception('Import failed: %s: module %s fn %s',
                                 str(err), module_name, fn)
                target_attr = None
            except AttributeError as err:
                logger.exception('Import failed: Module %s has no %s',
                                 module_name, fn)
                target_attr = None
    return target_attr


def import_multiple_classes(section, property_key):
    """
    Import multiple class names provided in the config file

    :type  section: :class:`str`
    :param section: Name of the section in the config file
    :type  property_key: :class:`str`
    :param property_key: Name of the property in the config file
    :rtype: :class:`list` of :class:`str`
    :return: List of class references
    """
    cfg = config.cfg
    classes = []
    if cfg and cfg.has_section(section) and cfg.has_option(section,
                                                           property_key):
        class_names = cfg.get(section, property_key).split(',')
        for class_name in class_names:
            class_name = class_name.strip()
            class_ref = dynamic_import(class_name)
            if class_ref is not None:
                classes.append(class_ref())

    return classes