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# JQ

JQ gives you a quick way to parse & filter JSONs into arrays. For instance, a good use case is parsing the JSON response of a REST service into an array.

{% code title="class.json" %}

```javascript
{
    'classes' : [
        {
            'class_name': '61a',
            'students': [
                {'name':'john', 'id':'1'},
                {'name':'kevin', 'id':'2'},
            ]
        },
        {
            'class_name': '61b',
            'students': [
                {'name':'alex', 'id':'3'},
                {'name':'bob', 'id':'4'},
            ]
        },
    ]
}
```

{% endcode %}

If we want an array of student-class memberships with all the meta-data down the tree captured, we can run a query like this.

```bash
jq [.classes[] | {class_name: .class_name, student: .students[] } | 
        {class_name: .class_name, name: .student.name, id: .student.id}]
```

This would produce an array of this kind:

```
[{class_name: 61a, student_name: john, id: 1}, ...]
```

I use this to wrap JQ for python:

{% embed url="<https://pypi.org/project/jq/>" %}

```
jq('.classes[] | {class_name: .class_name, student: .students[] } | 
        {class_name: .class_name, name: .student.name, id: .student.id}').transform(class.json)
```

### JQ Playground

Use a playground to make working with it much easier. Use this:

<https://jqplay.org/>