Level 4: Combining and reshaping · Exercise 47 of 63 · Pro

Orders with no customer, via indicator

A pandas exercise from Pandasdrill. Solve it with a Python editor in your browser running real pandas, and it is checked the moment you submit.

The task

Find the orders whose `cust_id` does not appear in `customers`. Use a left merge with indicator=True and keep only the left-only rows. Return the columns `order_id`, `cust_id`, `product_id` and `qty`. Row labels do not matter.

What this exercise teaches

The indicator column records where each merged row came from. After a left merge, left_only marks orders that found no customer, which is the anti-join analysts reach for when reconciling two systems. An outer merge would also pull in customers with no orders, whose order fields are NaN.

A hint if you get stuck

indicator=True adds a `_merge` column with the values left_only, right_only or both.