add import_object_ns function

To support bp:virt-driver-cleanup, there is a desire to have shorter
driver strings (i.e. libvirt.LibvirtDriver instead of
nova.virt.libvirt.LibvirtDriver). One way to support this is with
a new import_object variant that takes a namespace to load from.

If the code fails to load the driver in the prefered namespace it
will also try loading the full driver path, before throwing an
exception.

Change-Id: Ib97c92f38685ca89f29890f8015fc413acc744f8

1 files changed, 13 insertions, 0 deletions

diff --git a/openstack/common/importutils.py b/openstack/common/importutils.py
index 7654af5..933b54d 100644
--- a/openstack/common/importutils.py
+++ b/openstack/common/importutils.py
@@ -38,6 +38,19 @@ def import_object(import_str, *args, **kwargs):
     return import_class(import_str)(*args, **kwargs)
 
 
+def import_object_ns(name_space, import_str, *args, **kwargs):
+    """
+    Import a class and return an instance of it, first by trying
+    to find the class in a default namespace, then failing back to
+    a full path if not found in the default namespace.
+    """
+    import_value = "%s.%s" % (name_space, import_str)
+    try:
+        return import_class(import_value)(*args, **kwargs)
+    except ImportError:
+        return import_class(import_str)(*args, **kwargs)
+
+
 def import_module(import_str):
     """Import a module."""
     __import__(import_str)