在 PyYAML 中格式化自定义类输出
我正在研究一个简单的例子,但文档仍然让我有点困惑.
这是示例代码:
I'm working on a simple example here, but the docs still leave me a bit confused.
Here is the Example code:
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"]
!A val: !!python/object/apply:datetime.time ["\0\0\0\0\0\0"]
正确
因此,它似乎忠实地进行了 d-/序列化,但是默认的时间对象格式仍有一些不足之处.我怎样才能让它更漂亮,同时保持我强大的卸载/加载能力?
So, it appears to be faithfully d-/serializing, but the default time object format leaves something to be desired. How can I make it prettier while preserving my mighty dump/load powers?
谢谢
重新定义文档中所有时间的时间格式
您可以使用 datetime.time 实例定义自己的序列化格式">PyYAML 的代表"和构造函数".
Redefine time format for all times in a document
You can define your own serialization format for any datetime.time
instances in your documents using PyYAML 'representers' and 'constructors'.
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
只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.通过这种方式,您可以仅更改 A
的时间表示方式.YAMLObject 文档
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