Peeking into a class' API usage by smashing over __getattribute__

peek.py

from collections import namedtuple, defaultdict
from operator import itemgetter


ClassUsage = namedtuple('ClassUsage', 'cls attrs')
AttributeUsage = namedtuple('AttributeUsage', 'name count')
attrname = itemgetter(0)
attrcount = itemgetter(1)


def print_handler(data):
    print(data)


def peek(handler=None):
    if handler is None:
        handler = print_handler
    def class_decorator(cls):
        def printer(self, item):
            if not item.startswith('_'):
                if not hasattr(cls, "_attributes_used"):
                    cls._attributes_used = defaultdict(int)
                cls._attributes_used[item] += 1
                out = tuple(
                    AttributeUsage(name=attrname(x), count=attrcount(x))
                    for x in sorted(cls._attributes_used.items(), key=attrname)
                )
                usage = ClassUsage(cls=cls, attrs=out)
                handler(usage)
            return super(cls, self).__getattribute__(item)
        setattr(cls, '__getattribute__', printer)
        return cls
    return class_decorator


@peek()  # I can't figure out how to get rid of the parens :(
class Lol(...):
  pass

In an ideal world, one could do:

@peek
class Lol(...):

and it'd Just Work, defaulting to the print handler.
In reality, without the parens, handler is Lol, not None so one has to provide () to ensure immediate evaluation