Module 4: Multi-Step Analysis•25 min

Chaining Analysis Steps

Progress Tracking

Each variable is a checkpoint you can inspect. When something’s wrong, print any intermediate result to find the problem.

Name Your Variables Well

customer_totals tells you what’s in it. temp1 tells you nothing. Good variable names are documentation.

Adding Context with Merge

Tables: orders, customers

Ratios and Percentages

Percentage calculations follow a template: compute the per-group number, the total, then divide.

Table: employee

id	first_name	last_name	age	sex	employee_title	department	salary	target	bonus	email	city	address	manager_id
5	Max	George	26	M	Sales	Sales	1300	200	150	Max@company.com	California	2638 Richards Avenue	1
13	Katty	Bond	56	F	Manager	Management	150000	0	300	Katty@company.com	Arizona		1
11	Richerd	Gear	57	M	Manager	Management	250000	0	300	Richerd@company.com	Alabama		1
10	Jennifer	Dion	34	F	Sales	Sales	1000	200	150	Jennifer@company.com	Alabama		13
19	George	Joe	50	M	Manager	Management	100000	0	300	George@company.com	Florida	1003 Wyatt Street	1

Tables: employee

Customers with Large Orders

Table: online_store_customers

customer_id	customer_name
1	Alice Johnson
2	Bob Smith
3	Carol Williams
4	David Brown
5	Emma Davis

Table: online_store_orders

order_id	customer_id	amount	status
101	1	150	paid
102	1	200	paid
103	1	75	paid
104	2	250	paid
105	3	180	paid

Tables: online_store_customers, online_store_orders

Employee and Manager Salaries

Table: employee

id	first_name	last_name	age	sex	employee_title	department	salary	target	bonus	email	city	address	manager_id
5	Max	George	26	M	Sales	Sales	1300	200	150	Max@company.com	California	2638 Richards Avenue	1
13	Katty	Bond	56	F	Manager	Management	150000	0	300	Katty@company.com	Arizona		1
11	Richerd	Gear	57	M	Manager	Management	250000	0	300	Richerd@company.com	Alabama		1
10	Jennifer	Dion	34	F	Sales	Sales	1000	200	150	Jennifer@company.com	Alabama		13
19	George	Joe	50	M	Manager	Management	100000	0	300	George@company.com	Florida	1003 Wyatt Street	1

Tables: employee

Key Takeaways

Name each step as a variable — this is pandas’ equivalent of CTEs.
Each variable is a checkpoint you can inspect for debugging.
Chain: filter → group → aggregate → merge → filter again.
For ratios: compute numerator and denominator separately, then divide.

What’s Next

The final lesson covers common patterns you’ll use regularly: safe division, replacing slow loops, and knowing when a one-liner is better than multiple steps.

Next upContinue →

Patterns for Common Problems

35 min