Python 如何将嵌套字段添加到 Yaml 文件

Question

I need to modify a YAML file and add several fields.I am using the ruamel.yaml package.

First I load the YAML file:

data = yaml.load(file_name)

I can easily add new simple fields, like-

data['prop1'] = "value1"

The problem I face is that I need to add a nested dictionary incorporate with array:

prop2:
  prop3:
    - prop4:
        prop5:  "Some title" 
        prop6:  "Some more data"

I tried to define-

record_to_add = dict(prop2 = dict(prop3 = ['prop4']))

This is working, but when I try to add beneath it prop5 it fails-

record_to_add = dict(prop2 = dict(prop3 = ['prop4'= dict(prop5 = "Value")]))

I get

SyntaxError: expression cannot contain assignment, perhaps you meant "=="?

What am I doing wrong?

Answer 1

The problem has little to do with ruamel.yaml . This:

['prop4'= dict(prop5 = "Value")]

is invalid Python as a list ( [ ] ) expects comma separated values. You would need to use something like:

record_to_add = dict(prop2 = dict(prop3 = dict(prop4= [dict(prop5 = "Some title"), dict(prop6='Some more data'),])))

As your program is incomplete I am not sure if you are using the old API or not. Make sure to use

import ruamel.yaml
yaml = ruamel.yaml.YAML()

and not

import ruamel.yaml as yaml

Answer 2

Its because of having ['prop4'= <> ].Instead record_to_add = dict(prop2 = dict(prop3 = [dict(prop4 = dict(prop5 = "Value"))])) should work.

Another alternate would be,

import yaml

data = {
     "prop1": {
         "prop3":
             [{ "prop4":
                   {
                       "prop5": "some title",
                       "prop6": "some more data"
                   }
             }]
     }
 }

with open(filename, 'w') as outfile:
    yaml.dump(data, outfile, default_flow_style=False)