Package: convert2vars
convert2varsA small tool for mutual conversion of JSON, YAML with embedded parameters.
Parameter processing is handled by the powerful Jinja2 template engine.
JSON, which is often used in APIs, and YAML, which is adopted by popular platforms such as kubernetes (k8s) and ansible, can be converted to each other and dynamic parameter value editing can be performed.This document has been translated into English by machine translation. Please note that some parts may be inaccurate.[Japanese]Installation$ pip install convert2varsRequirementsPython 3.7 or laterUsageBasic UsageThe following simple example shows how to convert a k8s Deployment file.
This file contains two parameters (REPLICAS and CONTAINER_PORT), which are converted to the specified values by using the -e option.$ cat k8s-deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: {{ REPLICAS | default(2, True) }}
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: {{ CONTAINER_PORT | default(80, True) }}

$ convert2vars convert -e REPLICAS=4 -e CONTAINER_PORT=8080 -t k8s-deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 4
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx:1.14.2
        name: nginx
        ports:
        - containerPort: 8080Specifying ParametersParameter values can be specified in the following ways, or a combination of several methods.-e optionSpecify by command line option as described above. Multiple parameters can also be specified.Environment variablesAfter setting environment variables, execution with the -E option produces the same results as described above.$ export REPLICAS=4
$ export CONTAINER_PORT=8080
$ convert2vars convert -t k8s-deployment.yml -E--dotenv-file option can also be specified to use a combination of dotenv files.$ cat dotenv-temp
CONTAINER_PORT=8080
REPLICAS=4

$ convert2vars convert -t k8s-deployment.yml --dotenv-file dotenv-temp -EParameter filesBy using a file that enumerates parameters and their values, many parameters can be specified at once.JSON, YAML, and ini format files are available. The following three parameter files all produce the same results as in the example with the -e option described above.##JSONformat(k8s-parameter.json){"REPLICAS":3,"CONTAINER_PORT":8080}## YAML format (k8s-parameter.yml)REPLICAS:3CONTAINER_PORT:8080## ini format (k8s-parameter.ini)[default]REPLICAS=3CONTAINER_PORT=8080When using a parameter file, use the -i and -t options together.$ convert2vars convert -t k8s-deployment.yml -i k8s-parameter.jsonSpecifying complex parameter valuesParameter values with complex structures such as lists and hashes can be specified in JSON format.
Parameter values enclosed in [[] or {} are handled as JSON format.The following is an example of specifying a list and a hash as parameter values.$ cat complex_parameters.yml
instances: {{ TARGET_INSTANCES }}
instance_properties: {{ INSTANCE_PROPERTIES }}

$ convert2vars convert -e TARGET_INSTANCES='["vm01","vm02"]' -e INSTANCE_PROPERTIES='{"instance_type": "m1.small"}' -t complex_parameters.yml
instances: ['vm01', 'vm02']
instance_properties: {'instance_type': 'm1.small'}Also, by using a parameter file, complex parameter values can be specified in YAML as well as JSON. The following results are the same as the previous example with the -e option.$ cat complex_parameters.yml
TARGET_INSTANCES:
  - "vm01"
  - "vm02"
INSTANCE_PROPERTIES:
  instance_type: "m1.small"

$ convert2vars convert -i complex_parameters.yml -t complex_parameters.ymlTemplate engine supportThe filter, conditional branching, and iteration functions provided by Jinja2 can be used without modification. In the following example, since the parameter values are not explicitly specified, they are converted to the default values of 2 and 80 by Jinja2's default filter.$ convert2vars convert -t samples/templates/k8s-deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx:1.14.2
        name: nginx
        ports:
        - containerPort: 80Format ConversionFor JSON and YAML, it is possible to mutually convert formats.
In the following example, the -f option is used to convert to JSON format.
To perform format conversion, do not use the -t option, but specify the conversion source file as a parameter file with the -i option.$ convert2vars convert -e REPLICAS=4 -e CONTAINER_PORT=8080 -i k8s-deployment.yml -f json | jq .
{
  "apiVersion": "apps/v1",
  "kind": "Deployment",
  "metadata": {
    "name": "nginx-deployment"
  },
  "spec": {
    "replicas": 4,
    "template": {
      "metadata": {
        "labels": {
          "app": "nginx"
        }
      },
      "spec": {
        "containers": [
          {
            "name": "nginx",
            "image": "nginx:1.14.2",
            "ports": [
              {
                "containerPort": 8080
              }
            ]
          }
        ]
      }
    }
  }
}LicenseThe convert2vars module was written by Takeyuki Moriyama.
convert2vars is released under the MIT license.See the file LICENSE for more details.