Final assessment

Twelve questions across the whole course. Score 70% or more to pass and unlock your certificate. You can retake it as often as you like.

Finish every lesson to earn the certificate — you can take the assessment any time.

What does sum(float(v.replace(",", "")) for v in ["1,234.50", "99.00"]) return?

cancelled = orders[orders["status"] == "cancelled"] on Cartwheel’s orders. What is cancelled.shape?

messy["total"].sum() returns a long string instead of a number. Which first step diagnoses it?

messy["total"].round(2)
messy.drop_duplicates()
messy["total"].fillna(0)
messy["total"].dtype and a look at a few values, which reveal text such as "$65.00"

Support tickets can reference an order, and one order can have several tickets. Which validate fits orders.merge(tickets, on="order_id")?

You need the number of orders per customer, but only order_items (one row per line) is at hand. Which aggregation is right?

items.groupby("customer_id").size()
items.groupby("order_id").size()
Merge customer_id from orders, then groupby("customer_id")["order_id"].nunique()
items["order_id"].value_counts()

monthly is revenue per month for 2024 and 2025. Which expression compares each month with the same month a year earlier?

What label does pd.cut([100], bins=[0, 100, 200]) give to the value 100?

One order of 50,000 dollars is added by mistake to a table of 2,000 normal orders. Which statistic barely changes?

q4 = orders[in_q4] followed by q4["flag"] = True. What happens to orders under Copy-on-Write?

df["order_date"].str.contains("2025") works, but df["order_date"].dt.year fails. What does that tell you?

A quarter’s revenue rose 30%. Active customers rose 30%; orders per customer and average order value were flat. What is the best summary?

Which habit most protects a recurring monthly report from silently reporting wrong numbers when next month’s export changes format?

A cleaning function ending in assertions about ids, dates, totals and allowed values
Rounding every number to whole dollars
Running the notebook cells in a different order each month
Using errors="coerce" everywhere so nothing crashes

12 questions unanswered