Pretty Print JSON [Python One-Liner]

Problem: Given a JSON object. How to pretty print it from the shell/terminal/command line using a Python one-liner?

Minimal Example: You have given the following JSON object:

{"Alice": "24", "Bob": "28"}

And you want to get the following print output:

{
    "Alice": "24",
    "Bob": "28"
}

How to accomplish this using a Python one-liner?

Method 0: Python Program + json.dump

The default way to accomplish this in a Python script is to import the json library to solve the issue:

Exercise: Execute the script. What’s the output? Now change the number of indentation spaces to 2!

However, what if you want to run this from your operating system terminal as a one-liner command? Let’s dive into the four best ways!

Method 1: Terminal / Shell / Command Line with Echo + Pipe + json.tool

The echo command prints the JSON to the standard output. This is then piped as standard input to the json.tool program that pretty prints the JSON object to the standard output:

echo '{"Alice": "24", "Bob": "28"}' | python -m json.tool

The output is the prettier:

{
    "Alice": "24",
    "Bob": "28"
}

The pipe operator | redirects the output to the standard input of the Python script.

Method 2: Use a File as Input with json.tool

An alternative is the simple:

python -m json.tool file.json

This method is best if you have stored your JSON object in the file.json file. If the file contains the same data, the output is the same, too:

{
    "Alice": "24",
    "Bob": "28"
}

Method 3: Use Web Resource with json.tool

If your JSON file resides on a given URL https://example.com, you’ll best use the following one-liner:

curl https://example.com/ | python -m json.tool

Again, assuming the same JSON object residing on the server, the output is the same:

{
    "Alice": "24",
    "Bob": "28"
}

Method 4: Use jq

This is the simplest way but it assumes that you have the jq program installed on your machine. You can download jq here and also read about the excellent quick-start resources here.

Let’s dive into the code you can run in your shell:

jq <<< '{ "foo": "lorem", "bar": "ipsum" }'
{
  "bar": "ipsum",
  "foo": "lorem"
}

The <<< operator passes the string on the right to the standard input of the command on the left. You can learn more about this special pipe operator in this SO thread.

While this method is not a Python script, it still works beautifully when executed from a Linux or MacOS shell or the Windows Powershell / command line.

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