yaml.dump writes entire object, not just what's included in __repr__()

Say, I started with a short test program and trying the Monster class in the doc:

class Monster(yaml.YAMLObject):
    yaml_tag = u'!Monster'
    def __init__(self, name, hp, ac, attacks):
        self.name = name
        self.hp = hp
        self.ac = ac
        self.attacks = attacks
    def __repr__(self):
        return "%s(name=%r, hp=%r, ac=%r, attacks=%r)" % (
            self.__class__.__name__, self.name, self.hp, self.ac, self.attacks)

It worked fine at the beginning; but, when I started to enhance the class and include additional attributes, they all showed up in the YAML file…and, I would very much like to dictate what’s get written out…which I thought that was the purpose of the repr method.

How to only dump out hand-picked attributes?

[gsal]

Ha, nice! That was simple enought; got it working. Thanks.

[nitzmahone]

__repr__ is mainly about customizing how Python displays an object for human consumption when it’s printed, so it returns a string of whatever format you want (the Type(key1=value1, key2=value2) thing is a convention, you could return any string you want). __getstate__ is about dumping structured data for machine consumption (which is what pyyaml’s dumper needs).

The default behavior without that method defined just uses the dictionary returned by the internal __dict__ attribute that stores the attribute contents of a typical Python object. In this case, if you define a __getstate__ method to return a customized dictionary with only the stuff you want, it should have the desired effect, so long as you’re not also expecting to be able to round-trip these objects through some other serializer that relies on __getstate__ (as whatever state you omit from your dictionary will be lost in the translation).

def __getstate__(self):
    return dict(label_x=self.axlabel_x, label_y=self.axlabel_y)