关于解析：如何解析/读取YAML文件到Python对象？


How to parse/read a YAML file into a Python object?

如何将yaml文件解析/读取到python对象中？

例如，这个山药：

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Person:
  name: XYZ

到这个python类：

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class Person(yaml.YAMLObject):
  yaml_tag = 'Person'

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

顺便说一下，我用的是山药。

如果您的yaml文件如下所示：

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# tree format
treeroot:
    branch1:
        name: Node 1
        branch1-1:
            name: Node 1-1
    branch2:
        name: Node 2
        branch2-1:
            name: Node 2-1

您已经安装了PyYAML，如下所示：

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pip install PyYAML

python代码如下：

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import yaml
with open('tree.yaml') as f:
    # use safe_load instead load
    dataMap = yaml.safe_load(f)

变量dataMap现在包含一个包含树数据的字典。如果您使用预打印方式打印dataMap，您将得到如下信息：

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{'treeroot': {'branch1': {'branch1-1': {'name': 'Node 1-1'},
    'name': 'Node 1'},
    'branch2': {'branch2-1': {'name': 'Node 2-1'},
    'name': 'Node 2'}}}

所以，现在我们已经了解了如何将数据输入到我们的Python程序中。保存数据同样简单：

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with open('newtree.yaml',"w") as f:
    yaml.dump(dataMap, f)

您有一个字典，现在必须将其转换为python对象：

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class Struct:
    def __init__(self, **entries):
        self.__dict__.update(entries)

然后您可以使用：

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>>> args = your YAML dictionary
>>> s = Struct(**args)
>>> s
<__main__.Struct instance at 0x01D6A738>
>>> s...

并遵循"将python dict转换为object"。

有关更多信息，您可以查看pyyaml.org和这个。

相关讨论

来自http://pyyaml.org/wiki/pyyamldocumentation:

add_path_resolver(tag, path, kind)增加了一个基于路径的隐式标记解析器。路径是表示图中构成节点路径的键列表。路径元素可以是字符串值、整数或无。节点的类型可以是str、list、dict或none。

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#!/usr/bin/env python
import yaml

class Person(yaml.YAMLObject):
  yaml_tag = '!person'

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

yaml.add_path_resolver('!person', ['Person'], dict)

data = yaml.load("""
Person:
  name: XYZ
""")

print data
# {'Person': <__main__.Person object at 0x7f2b251ceb10>}

print data['Person'].name
# XYZ
相关讨论

这里有一种方法可以测试用户在virtualenv(或系统)上选择了哪些yaml实现，然后适当地定义load_yaml_file：

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load_yaml_file = None

if not load_yaml_file:
    try:
        import yaml
        load_yaml_file = lambda fn: yaml.load(open(fn))
    except:
        pass

if not load_yaml_file:
    import commands, json
    if commands.getstatusoutput('ruby --version')[0] == 0:
        def load_yaml_file(fn):
            ruby ="puts YAML.load_file('%s').to_json" % fn
            j = commands.getstatusoutput('ruby -ryaml -rjson -e"%s"' % ruby)
            return json.loads(j[1])

if not load_yaml_file:
    import os, sys
    print"""
ERROR: %s requires ruby or python-yaml  to be installed.

apt-get install ruby

  OR

apt-get install python-yaml

  OR

Demonstrate your mastery of Python by using pip.
Please research the latest pip-based install steps for python-yaml.
Usually something like this works:
   apt-get install epel-release
   apt-get install python-pip
   apt-get install libyaml-cpp-dev
   python2.7 /usr/bin/pip install pyyaml
Notes:
Non-base library (yaml) should never be installed outside a virtualenv.
"pip install" is permanent:
  https://stackoverflow.com/questions/1550226/python-setup-py-uninstall
Beware when using pip within an aptitude or RPM script.
  Pip might not play by all the rules.
  Your installation may be permanent.
Ruby is 7X faster at loading large YAML files.
pip could ruin your life.
  https://stackoverflow.com/questions/46326059/
  https://stackoverflow.com/questions/36410756/
  https://stackoverflow.com/questions/8022240/
Never use PyYaml in numerical applications.
  https://stackoverflow.com/questions/30458977/
If you are working for a Fortune 500 company, your choices are
1. Ask for either the"ruby" package or the"python-yaml"
package. Asking for Ruby is more likely to get a fast answer.
2. Work in a VM. I highly recommend Vagrant for setting it up.

""" % sys.argv[0]
    os._exit(4)


# test
import sys
print load_yaml_file(sys.argv[1])