pypyr.steps.fileformatjson permalink

find & replace tokens in json permalink

Parses input json file and substitutes {tokens} from the pypyr context.

Pretty much does the same thing as pypyr.steps.fileformat, only it makes it easier to work with curly braces for substitutions without tripping over the json’s structural braces.

Given input json like this:

  "k1": "v1",
  "k2": {
    "k2.1": "v2.1",
    "k2.2": [
      "START {replaceMeNested} END"
  "k3": "{replaceMeString}",
  "k4": "{replaceMeInt}",
  "k5": "{replaceMeBool}",
  "{replaceMeKey}": "this will replace the key"

And a pipeline like this:

  - name: pypyr.steps.fileformatjson
    comment: read json file, do some substitutions, write back out.
      replaceMeString: this was replaced by pypyr
      replaceMeInt: 420
      replaceMeBool: false
      replaceMeNested: doesn't matter where you are in the nesting structure
        in: ./sample-files/sample.json
        out: ./out/

The formatted output json file will be:

  "k1": "v1",
  "k2": {
    "k2.1": "v2.1",
    "k2.2": [
      "START doesn't matter where you are in the nesting structure END"
  "k3": "this was replaced by pypyr",
  "k4": 420,
  "k5": false,
  "keyfrompypyr": "this will replace the key"

type-safe token replacement permalink

Notice that you can replace values in the json document and keep the correct type - so numbers are numbers, booleans are booleans and so forth.

Even though you always have to set the "{replacement_expression}" inside quotes in the source json to ensure valid json, pypyr will output the correct type based on the value to which the expression evaluates.

You can also use replacement expressions in the json object’s keys.

multiple files & globs permalink

fileformatjson expects the following context keys:

  • fileFormatJson
    • in
      • Mandatory path(s) to source file on disk.
      • This can be a string path to a single file, or a glob, or a list of paths and/or globs.
      • Each path can be a glob, a relative or absolute path.
    • out (optional)
      • Write output file to here. Will create directories in path if these do not exist already.

See file format settings for more examples on in/out path handling - the same processing rules apply.

Example with a glob input:

  in: ./testfiles/sub3/**/*.txt
  # note the dir separator at the end.
  # since >1 in files, out can only be a dir.
  out: ./out/replace/

If you do not specify out, it will over-write (i.e in-place edit) all the files specified by in.

The file in and out paths support substitutions, which allows you to specify paths dynamically.

See a worked example of fileformatjson.

see also

last updated on .