Dynamic loading of classes

Question

My goal is to load dynamically my different subclasses and execute them. To call my script, I am using this:

python Plugin.py Nmap execute google.com

Or

python Plugin.py Dig execute google.com

Here it's the code

Parent Class: Plugin.py

class Plugin(object)
    def __init__(self):
        self.sName = ''
    def execPlugin(self):
        return 'something'
def main():
    # get the name of the plugin
    sPlugin = sys.argv[1]
    # create the object
    mMod = __import__(sPlugin, fromlist=[sPlugin])
    mInstance = getattr(mMod, sPlugin)
    oPlugin = mInstance()
    print oPlugin
    print type(oPlugin)
    if (sys.argv[2] == 'execute'):
        # then execute it
        return oPlugin.execPlugin(sys.argv[3])
if __name__ == '__main__':
    main()

Sub Class located in Nmap/Nmap.py

class Nmap(Plugin):
    def __init__(self):
        self.sName = 'Nmap'
    def execPlugin(self):
        return 'something else'

Sub Class located in Dig/Dig.py

class Dig(Plugin):
    def __init__(self):
        self.sName = 'Dig'
    def execPlugin(self):
        return 'yeahhh'

My problem is located in

oPlugin = mInstance()

With the following error

TypeError: 'module' object is not callable

I tried so many things but nothing worked. How can I solve my problem?

Why are Nmap.py and Dig.py in subdirectories? Do they have __init__.py files, and what's in those? You probably want another level of getattr to get the classes rather than the modules, or to simplify your structure. — jonrsharpe
– jonrsharpe, Commented Nov 4, 2015 at 16:00
Possible duplicate of TypeError: 'module' object is not callable — Ethan Bierlein
– Ethan Bierlein, Commented Nov 4, 2015 at 16:03
What happens if you e.g. from Nmap import Nmap in the __init__.py in /Nmap? I think that would fix it. — jonrsharpe
– jonrsharpe, Commented Nov 4, 2015 at 16:04
Then it's because you're importing the directory Nmap, not the file Nmap.py, as mMod, and therefore when you getattr from mMod you get Nmap.py not the class Nmap. Consider renaming to avoid this - modules should have snake_case names, only classes are CamelCase. — jonrsharpe
– jonrsharpe, Commented Nov 4, 2015 at 16:10

jonrsharpe · Accepted Answer · 2015-11-04 16:14:21Z

1

You have a structure like:

Plugin.py
/Nmap
    __init__.py
    Nmap.py
        # class Nmap(Plugin): ...

In Plugin.py, when you do mMod = __import__(sPlugin, fromlist=[sPlugin]) where sPlugin == 'Nmap', this makes mMod refer to the directory /Nmap, not the file Nmap.py (note that both files and directories can be modules in Python). Hence mInstance = getattr(mMod, sPlugin) makes mInstance the file Nmap.py rather than the class Nmap.

There are two ways to fix this, either:

Use the __init__.py in /Nmap to bring the class "up" one level, i.e. include from Nmap import Nmap; or
Add an extra level of getattr into Plugin.py.

Additionally, you should follow the style guide's naming conventions, which might have helped you track the issue down faster.

answered Nov 4, 2015 at 16:14

jonrsharpe

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1 Comment

David Over a year ago

You rock's ;). Thank you very much And yes, you're right, I will change my directory name :)

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