!!python/object:__main__.ClassName 抛出异常答案

【问题标题】：!!python/object:__main__.ClassName throwing exception!!python/object:__main__.ClassName 抛出异常
【发布时间】：2018-02-02 10:36:48
【问题描述】：

我有一个 YAML 文件：./YAML/simpleData.yml

- name: 'Somu'
  age:  26
  content:
  - name: 'Neo'
    age:  27
    content: []
  - name: 'Ari'
    age:  26
    content: []

我正在尝试通过以下方式使用 PyYAML 解析它：

import yaml
# Creating objects directly with the YAML module:
print("Attempting Direct Object Load: ")


class Person:
    def __init__(self, name, age, con):
        self.name = name
        self.age = hp
        self.content = con

    def __repr__(self):
        return "%s(name=%r, hp=%r, sp=%r)" % (
            self.__class__.__name__, self.name, self.age, self.content)

    def printData(self):
        print(self.name)
        print(self.age)
        if self.content:
            for per in self.content:
                print("-->", end="")
                per.printData()


# Data load:
person_obj = None
data = ""
try:
    with open('YAML/simpleData.yml') as source:
        for line in source:
            data += line
except Exception as err:
    print("An exception occurred: " + str(err))

person_obj = yaml.load("""!!python/object:__main__.Person\n""" + data)

if not person_obj:
    print("Data Loading Failed..! EXITING!!")
    exit(1)

person_obj.printData()

我是 Python 新手，因此无法确定我做错了什么，因此引发了此异常：

yaml.constructor.ConstructorError: expected a mapping node, but found sequence
  in "<unicode string>", line 1, column 1:
    !!python/object:__main__.Person
    ^

我该如何解决这个问题？

完整输出转储：

Attempting Direct Object Load: 
Traceback (most recent call last):
  File "/home/somu/Programming/python/HeadFirstPython/yamlIntro.py", line 106, in <module>
    person_obj = yaml.load("""!!python/object:__main__.Person\n""" + data)
  File "/home/somu/Programming/python/HeadFirstPython/venv/lib/python3.6/site-packages/yaml/__init__.py", line 72, in load
    return loader.get_single_data()
  File "/home/somu/Programming/python/HeadFirstPython/venv/lib/python3.6/site-packages/yaml/constructor.py", line 37, in get_single_data
    return self.construct_document(node)
  File "/home/somu/Programming/python/HeadFirstPython/venv/lib/python3.6/site-packages/yaml/constructor.py", line 46, in construct_document
    for dummy in generator:
  File "/home/somu/Programming/python/HeadFirstPython/venv/lib/python3.6/site-packages/yaml/constructor.py", line 578, in construct_python_object
    state = self.construct_mapping(node, deep=deep)
  File "/home/somu/Programming/python/HeadFirstPython/venv/lib/python3.6/site-packages/yaml/constructor.py", line 204, in construct_mapping
    return super().construct_mapping(node, deep=deep)
  File "/home/somu/Programming/python/HeadFirstPython/venv/lib/python3.6/site-packages/yaml/constructor.py", line 122, in construct_mapping
    node.start_mark)
yaml.constructor.ConstructorError: expected a mapping node, but found sequence
  in "<unicode string>", line 1, column 1:
    !!python/object:__main__.Person
    ^

Process finished with exit code 1

【问题讨论】：

错误信息说明了一切：需要映射（字典），但您的 YAML 文件包含序列（列表）。
@tinita 但是 YAML 模块不知道如何处理 YAML 数组吗？
当然 PyYAML 知道如何处理数组（序列）。但是 Person 对象需要序列化为映射。

标签： python yaml pyyaml

【解决方案1】：

在根源上，c.q.在您的文件的顶层，您有一个序列。其中第一个元素是键值对name:Somu 的映射。

如果你想以你描述的方式使用 PyYAML 加载它，你应该去掉每行的前两个字符：

data += line[2:]

或在第一个破折号后插入!!python/object:__main__.Person：

data = data.replace('- ', '- !!python/object:__main__.Person\n', 1)

【讨论】：