From 01b2b8c689cf2dfcfee5e21fe1b8277b09f5e8d8 Mon Sep 17 00:00:00 2001
From: Doug Hellmann <doug.hellmann@dreamhost.com>
Date: Wed, 14 Mar 2012 16:50:46 -0400
Subject: [PATCH] A utility function to import a class from a module given
 syntax such as used by nose and setuptools entry points.

---
 devstack/importer.py   | 19 +++++++++++++++++++
 tests/test_importer.py | 13 +++++++++++++
 2 files changed, 32 insertions(+)
 create mode 100644 devstack/importer.py
 create mode 100644 tests/test_importer.py

diff --git a/devstack/importer.py b/devstack/importer.py
new file mode 100644
index 00000000..31204f42
--- /dev/null
+++ b/devstack/importer.py
@@ -0,0 +1,19 @@
+
+
+def import_entry_point(fullname):
+    """Given a name import the class and return it.
+
+    The name should be in dotted.path:ClassName syntax.
+    """
+    if ':' not in fullname:
+        raise ValueError('Invalid entry point specifier %r' % fullname)
+    module_name, ignore, classname = fullname.partition(':')
+    try:
+        module = __import__(module_name)
+        for submodule in module_name.split('.')[1:]:
+            module = getattr(module, submodule)
+        cls = getattr(module, classname)
+    except (ImportError, AttributeError) as err:
+        raise RuntimeError('Could not load entry point %s: %s' %
+                           (fullname, err))
+    return cls
diff --git a/tests/test_importer.py b/tests/test_importer.py
new file mode 100644
index 00000000..07e80ea7
--- /dev/null
+++ b/tests/test_importer.py
@@ -0,0 +1,13 @@
+
+from devstack import importer
+from devstack import distro
+
+
+def test_function():
+    f = importer.import_entry_point('devstack.importer:import_entry_point')
+    assert f == importer.import_entry_point
+
+
+def test_class():
+    c = importer.import_entry_point('devstack.distro:Distro')
+    assert c == distro.Distro