Long → wide

Groups & reshaping · W23 · 8 MIN

Reshape unique identifier/measurement pairs.

Exercises within this concept

FollowFollow the techniqueCurrent exercise
ChangeAdapt a requirement
TransferChoose and combine

Understand the idea

pivot spreads a measurement-label column across new columns. It rearranges existing values without calculating a summary.

Illustration · not the exercise output

A small example

Ada · age · 4 and Ada · weight · 8 become one Ada row with age=4 and weight=8.

Follow the code

Apply the idea to the supplied table. Read from top to bottom; the final line displays the result.

long.pivot(index="candy", columns="measure", values="value")

What each part does

long.pivot(...): Reshape the supplied long table into wider rows.
index="candy": Use each candy name to identify an output row.
columns="measure": Turn each measure label into an output column.
values="value": Put each corresponding value into its new cell.

Your inputs

The editable setup on the right creates df and the additional inputs shown below. Run executes the setup and your work from top to bottom.

Candy shop · 6 synthetic rows
candy	flavour	price	rating	shelf
Gummy Bear	fruity	1.2	4.1	A
Choco Pop	chocolate	2.1	4.6	B
Mint Bite	mint	1.5	3.8	A
Berry Loop	fruity	2.8	4.4	B
Cocoa Cube	chocolate	3.4	4.9	A
Lemon Drop	fruity	1.8	4	B

long · prepared measurement table
candy	measure	value
Gummy Bear	price	1.2
Choco Pop	price	2.1
Mint Bite	price	1.5
Berry Loop	price	2.8
Cocoa Cube	price	3.4
Lemon Drop	price	1.8
Gummy Bear	rating	4.1
Choco Pop	rating	4.6
Mint Bite	rating	3.8
Berry Loop	rating	4.4
Cocoa Cube	rating	4.9
Lemon Drop	rating	4

Your task · Follow

The supplied long table contains candy, measure and value.
Pivot it back with candy on rows, measure on columns and value in cells.
Use: pivot().

Hint

pivot needs one value per identifier/measure pair and does not aggregate repeats.

Reveal solution

One way to do it. Keep any supplied setup in the editor and use this in the Your work section.

long.pivot(index="candy", columns="measure", values="value")

Optional stretch

Duplicate one row in long with pd.concat([long, long.head(1)]). Why does pivot reject it?

Your task · Follow

The supplied long table contains candy, measure and value.
Pivot it back with candy on rows, measure on columns and value in cells.
Use: pivot().

YOUR PYTHON

Tab: indent · Shift+Tab: outdent · Esc, then Tab: leave editor

# Supplied setup — editable
import pandas as pd

data = {
    "candy": [
        "Gummy Bear",
        "Choco Pop",
        "Mint Bite",
        "Berry Loop",
        "Cocoa Cube",
        "Lemon Drop",
    ],
    "flavour": ["fruity", "chocolate", "mint", "fruity", "chocolate", "fruity"],
    "price": [1.2, 2.1, 1.5, 2.8, 3.4, 1.8],
    "rating": [4.1, 4.6, 3.8, 4.4, 4.9, 4],
    "shelf": ["A", "B", "A", "B", "A", "B"],
}

df = pd.DataFrame(data)

long = df.melt(
    id_vars=["candy"],
    value_vars=["price", "rating"],
    var_name="measure",
    value_name="value",
)

# Your work
# Build the requested result from the given table
result = ____
result

Each run executes all editor code in a fresh Python session. Display a value by leaving it on the final line.

Python starts when you open a lesson.

Output

Run your code to see what Python returns.