pypyr.steps.jsonparse

parse json string into context object

Parse an input json string into the pypyr context as an object. This allows you to work with the deserialized objects from the json string like you would normally work with any data structures in the pypyr context - so you can use all the usual context handling functionality to set, edit & manipulate context keys and values.

This step requires the jsonParse key in the pypyr context:

- name: pypyr.steps.jsonparse
  comment: parse json from string
  in:
    jsonParse:
      json: '[1, 2, 3]' # required. string of json.
      key: destinationKey # optional. write result object to this context key.

If you do not specify key, json writes directly to context root.

All inputs support substitutions.

parse the json output of preceding steps

Keep in mind that yaml is a superset of json. Specifically yaml 1.2, which is what a pypyr pipeline uses. This means that if you did want to put a literal bit of json anywhere in the pipeline, you can do so without bothering with parsejson.

- name: pypyr.steps.set
  comment: put hard-coded json document into pipeline context.
           notice for both the map & the list we're directly
           using valid json syntax.
           this works because yaml is a superset of json.
  in:
    set:
      myList: [1, 2, 3]
      myMap: {"a": "b", "c": "d"}

This parsejson step only really becomes necessary when you want to parse a value that is a string already - likely the output of a command you executed in a preceding step.

You are very like to use parsejson using the ff flat format directive to prevent pypyr from interpreting the json’s {curly braces} as pypyr formatting expressions:

- name: pypyr.steps.jsonparse
  in:
    jsonParse:
      json: '{myJsonString:ff}'
      key: myParsedJson

example

In this pipeline we curl a json string from a REST api web-server and load the response json string into context using jsonparse.

- name: pypyr.steps.cmd
  description: --> curl some json from the awesome httpbin.org
  comment: because save is True, output saves to cmdOut.
  in:
    cmd:
      run: |-
        curl -H 'Content-Type: application/json' -X GET https://httpbin.org/json        
      save: True

- name: pypyr.steps.echo
  in:
    echoMe: "the response string from curl:\n{cmdOut[stdout]} "

- name: pypyr.steps.jsonparse
  description: --> parsing curl response string into context
  in:
    jsonParse:
      json: '{cmdOut[stdout]:ff}'
      key: myParsedJson

- name: pypyr.steps.echo
  in:
    echoMe: |
      the json response from the curl cmd is in context now.
      slideshow.title: {myParsedJson[slideshow][title]}
      arbitrary slide item: {myParsedJson[slideshow][slides][1][items][0]}      

Here is a worked example of jsonparse.

json structure

pypyr will merge the json parsed from the input string into the pypyr context. This will overwrite existing values if the same keys already exist in context.

I.e if json string has {'eggs' : 'boiled'}, but context {'eggs': 'fried'} already exists, after jsonparse the key context['eggs'] will be ‘boiled’.