According to:

http://libvirt.org/html/libvirt-libvirt.html#virNetworkLookupByUUID

virNetworkLookupByUUID() expects a virConnectPtr as its first argument,
thus making it a method of the virConnect Python class.

Currently it's a method of libvirt.virNetwork.

@@ -805,13 +805,6 @@ class virNetwork:
         if ret == -1: raise libvirtError ('virNetworkGetAutostart() failed', net=self)
         return ret

-    def networkLookupByUUID(self, uuid):
-        """Try to lookup a network on the given hypervisor based on its UUID. """
-        ret = libvirtmod.virNetworkLookupByUUID(self._o, uuid)
-        if ret is None:raise libvirtError('virNetworkLookupByUUID() failed', net=self)
-        __tmp = virNetwork(self, _obj=ret)
-        return __tmp
-
 class virInterface:
     def __init__(self, conn, _obj=None):
         self._conn = conn
@@ -1689,6 +1682,13 @@ class virConnect:
         __tmp = virDomain(self,_obj=ret)
         return __tmp

+    def networkLookupByUUID(self, uuid):
+        """Try to lookup a network on the given hypervisor based on its UUID. """
+        ret = libvirtmod.virNetworkLookupByUUID(self._o, uuid)
+        if ret is None:raise libvirtError('virNetworkLookupByUUID() failed', conn=self)
+        __tmp = virNetwork(self, _obj=ret)
+        return __tmp
+