#!/usr/bin/env python3

from operator import itemgetter
import json

items = [
    {
        'url': 'http://aaa/',
        'user': 'xxx',
        'quota': 100,
    },
    {
        'url': 'http://aaa/',
        'user': 'yyy',
        'quota': 200,
    },
    {
        'url': 'http://bbb/',
        'user': 'xxx',
        'quota': 100,
    },
    {
        'url': 'http://bbb/',
        'user': 'yyy',
        'quota': 200,
    },
]

keyspec = [
    (itemgetter('url'), False),
    (itemgetter('user'), True),
]

def keygen(ks):
    class _:
        def __init__(self, v): self.v = v
        def __eq__(self, o): return o.v == self.v
        def __lt__(self, o): return o.v < self.v
    return lambda x: [ _(k(x)) if r else k(x) for k, r in ks ]

items.sort(key=keygen(keyspec))

print(json.dumps(items, indent=4))