Can not import class from another path - ValueError: Empty module name

Question

I followed advice here on stackoverflow on how to import a class from a path outside of the root folder: How to dynamically load a Python class Does python have an equivalent to Java Class.forName()?

Unfortunately this raises the error: ValueError: Empty module name

It is my understanding that import should not return an empty module, like the load_source method from imp. So I do not understand this error nor how to approach it.

What am I implementing wrong here? Could you tilt me into the right direction here?

Thanks!

Code:

klass = __import__('..folder.module.Class_A')
some_object = klass()

class class_B(some_object):
    def run(self):
        print ('Test OK!')

Imported class (content of module):

class Class_A():
    def __init__(self, arg1, *args):
def run(self):
    pass

"__import__('..folder.module.Class_A')" is not what is suggested in your link. I suggest you reread it. — Veedrac
– Veedrac, Commented Sep 20, 2014 at 1:38

user3885927 · Accepted Answer · 2014-09-20 03:40:41Z

First of all you are not using import correctly.

Option 1:

According to https://docs.python.org/2/library/functions.html#import you should be doing:

klass = __import__('folder.module', globals(), locals(), ['Class_A'], -1)

Now if you want Class_A itself you should do:

some_object = klass.Class_A

Then you can inherit from it using:

class class_B(some_object):
    def run(self):
        print ('Test OK!')

Option 2:

from folder.module import Class_A

Then you can inherit from it using:

class class_B(Class_A):
    def run(self):
        print ('Test OK!')

Note: In folder.module folder should be a python package and module should be a python module

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