is there similar syntax to php's $$variable in python

Question

is there similar syntax to php's $$variable in python? what I am actually trying is to load a model based on a value.

for example, if the value is Song, I would like to import Song module. I know I can use if statements or lambada, but something similar to php's $$variable will be much convenient.

what I am after is something similar to this.

from mypackage.models import [*variable] 

then in the views

def xyz(request): 
    xz = [*variable].objects.all() 

*variable is a value that is defined in a settings or can come from comandline. it can be any model in the project.

Answer 1

def load_module_attr (path):
    modname, attr = path.rsplit ('.', 1)
    mod = __import__ (modname, {}, {}, [attr])
    return getattr (mod, attr)

def my_view (request):
    model_name = "myapp.models.Song" # Get from command line, user, wherever
    model = load_module_attr (model_name)
    print model.objects.all()

Answer 2

I'm pretty sure you want __import__() .

Read this: docs.python.org: __import__

This function is invoked by the import statement. It can be replaced (by importing the builtins module and assigning to builtins.__import__ ) in order to change semantics of the import statement, but nowadays it is usually simpler to use import hooks (see PEP 302 ). Direct use of __import__() is rare, except in cases where you want to import a module whose name is only known at runtime.

Answer 3

It seems that you want to load all the potentially matchable modules/models on hand and according to request choose a particular one to use. You can "globals()" which returns dictionary of global level variables, indexable by string. So if you do something like globals()['Song'], it'd give you Song model. This is much like PHP's $$ except that it'll only grab variables of global scope. For local scope you'd have to call locals().

Here's some example code.

from models import Song, Lyrics, Composers, BlaBla

def xyz(request):
    try:
        modelname = get_model_name_somehow(request):
        model =globals()[modelname]
        model.objects.all()
    except KeyError:
        pass # Model/Module not loaded ... handle it the way you want to 

Answer 4

So you know the general concept, what you are trying to implement is known as "Reflective Programming".

You can see examples in several languages in the wikipedia entry here

http://en.wikipedia.org/wiki/Reflective_programming