from random import randint

varss = [{'id': x, 'parent': randint(0, 10)} for x in range(10)]
vars_ = [{'id': x, 'parent': None} for x in range(10, 15)]
vars_ += varss


def pretty(d, indent=0):
    if isinstance(d, list):
        for x in  d: 
            pretty(x, indent + 1)
    else:
        for key, value in d.iteritems():
            print ('\t' * indent + str(key))
            if isinstance(value, dict):
                pretty(value, indent + 1)
            else:
                print('\t' * (indent + 1) + str(value))
    

def sort_tree(items):
    res = []
    first_column = [x for x in items if x.get('id') == 0 or
                    x.get('parent') is None]
    first_column = sorted(
        first_column, key=lambda y: y.get('id'))  # reverse=True
    items_dict = {}
    for x in items:
        x['children'] = []
        items_dict[x['id']] = x
    items = sorted(items, key=lambda y: y.get('id'))
    for x in items:
        id = x.get('parent')
        if not id:
            continue
        items_dict[id]["children"].append(x)
    print(items)
    return first_column 
# print(vars_)
print(pretty(sort_tree(vars_)))