lazy_debug.py

class DebugMeta(type):
    def __bool__(self):
        global is_debug
        return is_debug

class DEBUG(object, metaclass=DebugMeta):
    def __init__(self, message):
        if not type(self):
            return
        print(message() if callable(message) else message)


def compute(arg):
    print('computing!')
    return arg


is_debug = True
DEBUG and DEBUG(compute('one'))
DEBUG(lambda: compute('two'))

is_debug = False
DEBUG and DEBUG(compute('three'))
DEBUG(lambda: compute('four'))