Pretty-print JSON with the standard library

A JSON response is on one line and jq is not installed, but Python is.

echo '{"name":"demo","tags":["a","b"],"n":1}' | python3 -m json.tool
echo '{"b":1,"a":2}' | python3 -m json.tool --sort-keys --indent 2
echo '{"a": 1,}' | python3 -m json.tool; echo "exit: $?"

{
    "name": "demo",
    "tags": [
        "a",
        "b"
    ],
    "n": 1
}
{
  "a": 2,
  "b": 1
}
Expecting property name enclosed in double quotes: line 1 column 9 (char 8)
exit: 1

json.tool reads standard input or a file, parses it with the json module and prints it with an indent, as described in the json.tool documentation. The key order of the input is kept unless you add --sort-keys. A trailing comma is not valid JSON, and the parser reports the line and column of the error and exits with status 1.

Non-ASCII characters are written as escape sequences by default, so add --no-ensure-ascii on Python 3.9 or later to keep them readable. The tool loads the whole document into memory, and the input must be a single JSON value, so a stream of JSON lines needs --json-lines from Python 3.8.