python, instance dynamic module.class from given path package and call dynamic method

Question

package_path = '/home/foo/bar/'
module_class = 'hello.World'
method = 'something'

first, i want to import the hello module what it is inside of the package_path (/home/foo/bar/)

then, i must instantiate the class World at this module

and finally i should run the something() method on the new world_instance_object

any idea for do that?

Thank you so much!

this can be duplicate for stackoverflow.com/questions/67631/… — oleg
– oleg, Commented Sep 20, 2013 at 21:45
any way for import a package (not module) from path string and then, import the module.Class for them? — fj123x
– fj123x, Commented Sep 20, 2013 at 22:14
package and module are imported same way. class is module attribute, method is class atribute. Use getattr for obtaining object's attribute — oleg
– oleg, Commented Sep 20, 2013 at 22:17

kindall · Accepted Answer · 2013-09-22 01:57:36Z

To avoid having to manipulate sys.path and to keep all the extra modules you import from cluttering up sys.modules, I'd suggest using execfile() for this. Something like this (untested code):

import os.path

def load_and_call(package_path, module_class, method_name):
    module_name, class_name = module_class.split(".")
    module_globals = {}
    execfile(os.path.join(package_path, module_name + ".py"), module_globals)
    return getattr(module_globals[class_name](), method_name, lambda: None)()

You could add some code to cache the parsed objects using a dictionary, if a file will be used more than once (again, untested):

def load_and_call(package_path, module_class, method_name, _module_cache={}):
    module_name, class_name = module_class.split(".")
    py_path = os.path.join(package_path, module_name + ".py")
    module_globals = _module_cache.setdefault(py_path, {})
    if not module_globals:
        execfile(py_path, module_globals)
    return getattr(module_globals[class_name](), method_name, lambda: None)()

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