Question

I want a dict or tuple I can sort based on attributes of the objects I’m using as arguments for *arg. The way I’ve been trying to do it just gives me AttributeErrors, which leads me to believe I’m doing it weird.

def function(*arg):
    items = {}
    for thing in arg:
        items.update({thing.name:thing})


    while True:
        for thing in items:
        ## lots of other code here, basically just a game loop.
        ## Problem is that the 'turn order' is based on whatever
        ## Python decides the order of arguments is inside "items".
        ## I'd like to be able to sort the dict based on each object's
        ## attributes (ie, highest 'thing.speed' goes first in the while loop)

The problem is when I try to sort “items” based on an attribute of the objects I put into function(), it gives me “AttributeError: ‘str’ object has no attribute ‘attribute'”. Which leads me to believe I’m either unpacking *arg in a lousy way, or I’m trying to do something the wrong way.

while True:
    for thing in sorted(items, key=attrgetter('attribute')):

…doesn’t work either, keeps telling me I’m trying to manipulate a ‘str’ object. What am I not doing here?

Answer 1

arg already is a tuple you can sort by an attribute of each item:

def function(*args):
    for thing in sorted(args, key=attrgetter('attribute')):

When you iterate over a dict, as sorted is doing, you just get the keys, not the values. So, if you want to use a dict, you need to do:

def function(*args):
    # or use a dict comprehension on 2.7+ 
    items = dict((thing.name, thing) for thing in args)

    # or just items.values on 3+
    for thing in sorted(items.itervalues(), key=attrgetter('attribute')):

to actually sort the args by an attribute. If you want the keys of the dict available as well (not necessary here because the key is also an attribute of the item), use something like:

for name, thing in sorted(items.iteritems(), key=lambda item: item[1].attribute):