在 PyYAML 中格式化自定义类输出

我正在这里研究一个简单的示例，但文档仍然让我有点困惑。
这是示例代码：

class A(yaml.YAMLObject):
    yaml_tag = u'!A'

    def __init__(self, val):
        self.val = val

if __name__ == '__main__':
    t = datetime.time()
    a = A(t)
    print yaml.dump(a)
    print yaml.load(yaml.dump(a)).val == t

输出是

!A val: !!python/object/apply:datetime.time ["\0\0\0\0\0\0"]

True

因此，它似乎是忠实的数据/序列化，但默认的时间对象格式还有一些不足之处。我怎样才能让它更漂亮，同时保留我强大的转储/负载能力？

Thanks

重新定义文档中所有时间的时间格式

您可以为任何内容定义自己的序列化格式datetime.time文档中的实例使用PyYAML“代表者”和“构造者” http://pyyaml.org/wiki/PyYAMLDocumentation#Constructorsrepresentersresolvers.

import datetime

import yaml

time_format = '%H:%M:%S'


def time_representer(dumper, data):
    return dumper.represent_scalar(u'!time', data.strftime(time_format))


def time_constructor(loader, node):
    value = loader.construct_scalar(node)
    return datetime.datetime.strptime(value, time_format).time()


yaml.add_representer(datetime.time, time_representer)
yaml.add_constructor(u'!time', time_constructor)


class A(yaml.YAMLObject):
    yaml_tag = u'!A'

    def __init__(self, val):
        self.val = val


if __name__ == '__main__':
    t = datetime.time()
    a = A(t)
    print yaml.dump(a, default_flow_style=False)
    print yaml.load(yaml.dump(a)).val == t

将输出：

!A
val: !time '00:00:00'

True

仅为特定班级重新定义时间格式

您还可以定义特定类如何序列化和反序列化。这样你就可以改变时间的表示方式A only. YAMLObject 的文档 http://pyyaml.org/wiki/PyYAMLDocumentation#YAMLObject

import datetime

import yaml

time_format = '%H:%M:%S'

class A(yaml.YAMLObject):
    yaml_tag = u'!A'

    def __init__(self, val):
        self.val = val

    @classmethod
    def to_yaml(cls, dumper, data):
        dict_representation = {
            'val':data.val.strftime(time_format)
        }
        node = dumper.represent_mapping(u'!A', dict_representation)
        return node

    @classmethod
    def from_yaml(cls, loader, node):
        dict_representation = loader.construct_mapping(node)
        val = datetime.datetime.strptime(
            dict_representation['val'], time_format).time()
        return A(val)

if __name__ == '__main__':
    t = datetime.time()
    a = A(t)
    print yaml.dump([t,a], default_flow_style=False)

    loaded = yaml.load(yaml.dump([t,a]))
    print loaded[0] == t
    print loaded[1].val == t

将输出：

- !!python/object/apply:datetime.time
  - "\0\0\0\0\0\0"
- !A
  val: 00:00:00

True
True