Question

I’m a complete nab with python.
But now I need a simple storage containing MyObject-objects for some project.
Each object contains a few StringProperties nothing fancy.

Now I want to get from my list of MyObjects, 10 random objects and store them in some other array.

So I went searching and found random.sample and started implemending it.

def get10RandomMyObjects():
    # waarders maken
    dict = {}
    myObjectsList = []

    # Lijst vullen
    myObjects = MyObject.all()

    randomMyObjects = random.sample(myObjects, 10)

    for o in randomMyObjects:
        dict_myObject = { }
        #some random property setting
        myObjectsList.append(dict_myObject)

    dict['myObjects'] = myObjectsList
    return dict

This is the error I get back:

 File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/random.py", line 314, in sample
    n = len(population)
TypeError: object of type 'Query' has no len()

So obviously something is wrong with the random.sample but my noobness can’t decypher what it is.
Anyone care to explain me why I can’t obtain those 10 random MyObjects I so desire?

Answer 1

random.sample() works on lists. Obviously, MyObject.all() does not return a list but a Query object. If Query is at least iterable then you can write:

myObjects = list(MyObject.all())

Otherwise, you have to create a list from MyObject.all() manually.