Python lesson

New columns

Maths on a column runs on every row at once. It's like writing a formula once and filling it down the whole column.

About 5–10 minutes · no sign-up needed

Example

One line creates a VAT column for all eight orders:

df["VAT"] = df["Revenue"] * 0.075
df.head()

Output:

Order Day Store Product Qty Revenue VAT
0 O101 Mon Lagos Earbuds 2 70 5.25
1 O102 Mon Abuja Charger 1 15 1.125
2 O103 Tue Lagos Phone case 3 24 1.7999999999999998
3 O104 Wed Lagos Earbuds 1 35 2.625
4 O105 Wed Abuja Earbuds 4 140 10.5

Key points

df["VAT"] = ...Create a new column. Every row gets its own answer.

df["Revenue"] * 0.075Maths on a column happens on every row.

df["Revenue"] / df["Qty"]Two columns can be combined, row by row.

Put together: df["Price"] = df["Revenue"] / df["Qty"].

Practice

Try each one in your head first, then open the answer.

1. Build a line that adds a column called Double: revenue times 2.

df["Double"] = df["Revenue"] * 2

2. Build a line that adds a column called Price: revenue divided by quantity.

df["Price"] = df["Revenue"] / df["Qty"]

3. Add a column called Price: revenue divided by quantity.

df["Price"] = df["Revenue"] / df["Qty"]

4. Add a column called VAT: revenue times 0.075.

df["VAT"] = df["Revenue"] * 0.075

5. Add a column called Bonus: quantity times 5.

df["Bonus"] = df["Qty"] * 5

Learn it by doing. This lesson is a short hands-on level on Bampaa: see it work, then build and write it yourself, with instant feedback.

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About 5–10 minutes · no sign-up needed