Question

I have a module from a child package that is imported dynamically; how can I iterate over the classes that it contains?

I have been importing the module and listing the names like this:

package = current_module.__name__
package = package[:package.rindex(".")] # get the package
package = "%s.sub.%s"%(package,name) # make the name of the child
print "(loading package %s)"%package
module = __import__(package) # this succeeds
for name,obj in inspect.getmembers(module):
    print name,type(obj)

This only prints module attributes and not the class types that the module defines:

__builtins__ <type 'dict'>
__doc__ <type 'NoneType'>
__file__ <type 'str'>
__name__ <type 'str'>
__package__ <type 'NoneType'>
__path__ <type 'list'>
imported_package <type 'module'>

---

It seems that my classes are not in the __dict__ unless the fromlist is non-empty! The values in the from-list don’t seem to be validated though; [""] seems to work just fine, and suddenly the classes show up!

Can anyone explain why this is?

(Standard ubuntu python 2.7.1+ (r271:86832)

Answer 1

Example: to create a dict that maps the names to the classes:

dict([(name, cls) for name, cls in mod.__dict__.items() if isinstance(cls, type)])

where mod is the loaded module