[Zope] Checking for ID's before creating ZClass

Hello from rainy England, In my constructor for a ZClass I want to auto generate an ID consisting of a name followed by a incrementing sequence (port0, port1, port2...). How do I check for all existing id's in a folder? I tried doing it in a PythonMethod (or whatever they are called now!), calling hasattr() but failed. Another possibilty would be to loop on a try..<createInObject>..raise until successful, but that doesn't seem very zopish. In the source code for createInObjectManager I can see it getting the folder, but can't figure how to acheive that directly, Ivan