User-Defined Fields

The Problem

User-defined fields allow you to pivot a table. For example, given this data:

[
    {
        "name": "Robert Pringles",
        "address": "Earth",
        "email": "bob@pringles.pop",
        "title": "CEO"
    },
    {
        "name": "Daniel Sausage",
        "address": "Mars",
        "email": "danny@pringles.pop",
        "title": "Head Chef"
    },
    {
        "name": "Charlie Marmalade",
        "address": "Pluto",
        "email": "charlie@pringles.pop",
        "title": "CTO"
    }
]

–we already know how to create table like this:

No User-Defined Fields

Name	Address	Email	Title
Robert Pringles	Earth	bob@pringles.pop	CEO
Daniel Sausage	Mars	danny@pringles.pop	Head Chef
Charlie Marmalade	Pluto	charlie@pringles.pop	CTO

–but we might prefer to pivot that same data like this:

User-Defined Fields

Name	Property	Value
Robert Pringles	Address	Earth
Robert Pringles	Email	bob@pringles.pop
Robert Pringles	Title	CEO
Daniel Sausage	Address	Mars
Daniel Sausage	Email	danny@pringles.pop
Daniel Sausage	Title	Head Chef
Charlie Marmalade	Address	Pluto
Charlie Marmalade	Email	charlie@pringles.pop
Charlie Marmalade	Title	CTO

We’ll achieve this by using a ByUserDefinedFields group type.

Code Sample

This code is similar to the Flat Table example, but note:

1. A ByUserDefinedFields instance is created and the user-defined fields are appended. Just like with columns, the first argument is the name and the second is the path to the data.

2. The ByUserDefinedFields instance is set as the column set’s group.

3. Two Property and Value columns are added to include the field names and values in the render. The names can be anything you want, but the paths must be the ByUserDefinedFields.NAME and ByUserDefinedFields.VALUE tokens.

from rolumns import ByUserDefinedFields, Columns, Source
from rolumns.renderers import RowsRenderer

data = [
    {
        "name": "Robert Pringles",
        "address": "Earth",
        "email": "bob@pringles.pop",
        "title": "CEO"
    },
    {
        "name": "Daniel Sausage",
        "address": "Mars",
        "email": "danny@pringles.pop",
        "title": "Head Chef"
    },
    {
        "name": "Charlie Marmalade",
        "address": "Pluto",
        "email": "charlie@pringles.pop",
        "title": "CTO"
    }
]

columns = Columns()
columns.add("Name", "name")

group = ByUserDefinedFields()
group.append("Address", "address")
group.append("Email", "email")
group.append("Title", "title")

udfs = columns.group(group)
udfs.add("Property", ByUserDefinedFields.NAME)
udfs.add("Value", ByUserDefinedFields.VALUE)

renderer = RowsRenderer(columns)
rows = renderer.render(data)

print(list(rows))

Result

 [['Name',              'Property', 'Value'],
  ['Robert Pringles',   'Address',  'Earth'],
  ['Robert Pringles',   'Email',    'bob@pringles.pop'],
  ['Robert Pringles',   'Title',    'CEO'],
  ['Daniel Sausage',    'Address',  'Mars'],
  ['Daniel Sausage',    'Email',    'danny@pringles.pop'],
  ['Daniel Sausage',    'Title',    'Head Chef'],
  ['Charlie Marmalade', 'Address',  'Pluto'],
  ['Charlie Marmalade', 'Email',    'charlie@pringles.pop'],
  ['Charlie Marmalade', 'Title',    'CTO']]