Pretty-print JSON with Go

Today, we have a simple recipe to pretty-print JSON using Golang:

 1package main
 2
 3import (
 4    "bytes"
 5    "encoding/json"
 6    "fmt"
 7    "log"
 8)
 9
10func formatJSON(data []byte) ([]byte, error) {
11    var out bytes.Buffer
12    err := json.Indent(&out, data, "", "    ")
13    if err == nil {
14        return out.Bytes(), err
15    }
16    return data, nil
17}
18
19func main() {
20
21    data := []byte(`{"key":"hello","msg":"world"}`)
22
23    prettyJSON, err := formatJSON(data)
24    if err != nil {
25        log.Fatal(err)
26    }
27
28    fmt.Println(string(prettyJSON))
29
30}

Run this in the Go Playground.

The idea is that we take a byte slice of JSON data and then use the json.Indent method to format it. It's signature is as follows:

1func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error

Indent appends to dst an indented form of the JSON-encoded src. Each element in a JSON object or array begins on a new, indented line beginning with prefix followed by one or more copies of indent according to the indentation nesting. The data appended to dst does not begin with the prefix nor any indentation, to make it easier to embed inside other formatted JSON data. Although leading space characters (space, tab, carriage return, newline) at the beginning of src are dropped, trailing space characters at the end of src are preserved and copied to dst. For example, if src has no trailing spaces, neither will dst; if src ends in a trailing newline, so will dst.

To accomplish the same in Python, you can do:

 1import json
 2
 3def formatJSON(input):
 4    parsed = json.loads(input)
 5    return json.dumps(parsed, indent=4)
 6
 7def main():
 8    
 9    data = '{"key":"hello","msg":"world"}'
10    
11    pretty_json = formatJSON(data)
12
13    print(pretty_json)
14
15if __name__ == "__main__":
16    main()