class Foo():
  def my_method(self):
    return 3107


class Bar():
  def my_method(self):
    return 7013

def factory(klass):
  if klass == 'Foo':
    return Foo()
  elif klass == 'bar':
    return Bar()

factory('Foo').my_method()
  => 3107


OR

print 'Foo'.constantize.my_method()
=> 3107