Updated . Built against the tool’s current screens and checked step by step. How we check this lesson
A beginner Python walkthrough in the free Google Colab: label three monthly exports, stack them into one quarter with pandas concat and total by month and by customer, typing every line yourself.
At a glance
| Question | Answer |
|---|---|
| What you build | A beginner Python walkthrough in the free Google Colab: label three monthly exports, stack them into one quarter with pandas concat and total by month and by customer, typing every line yourself. |
| Tools | Google Colab |
| Time | About 12 minutes, 11 steps in 3 parts |
| Level | Beginner, no coding needed |
| Cost | Free |
| Ways to learn it | Practice it step by step |
The 3 parts, in short
- Three monthly exports: July's export, August's export, September's export.
- Stack them: Label each month, Run it, Stack the three months, Run it.
- Totals by month and customer: Total each month, Run it, Total each customer, Run it.
Start here first: Python: Total a Sales Export by Customer in Google Colab (module 1 of Python)
What you'll build
The sales system at Lakeside Office Supply (made up) exports one file per month. For the quarterly review someone copies July, August and September under each other in a spreadsheet, fixes the headers that got pasted three times and hopes nothing was skipped. In this lesson you do it in Google Colab with pandas: three small monthly tables, a month label on each, one line that stacks them, and totals by month and by customer. You type every line yourself.
July $2,110, August $2,950 and September $2,870: $7,930 in all, with Cobalt Legal on top at $3,170. With real files, pd.read_csv loads each month and the rest is the same. Do it in Colab yourself: the lesson page has the checklist.
- Tools: Google Colab
- Time: about 12 minutes, 11 steps in 3 chapters
- Level: beginner, no coding needed
- Price: free
Practice first, then build it for real
Practice copy built from real Google Colab screens (captured 24 October 2026). Every line of Python in it was typed and run there. Nothing here touches your Google account. Our account shows a PRO badge; everything in the lesson works the same in free Colab. The shop, its customers and its numbers are made up, and the account picture is blurred. To build it for real you need your own Google Colab account, and some services charge once you use them for real work, so check each tool's current pricing.
Try it yourself, free
Reading the steps is a start. Doing them is how it sticks. The interactive module walks you through every click in a practice copy of Google Colab, checks each step, and never touches your real accounts.
Start “Python: Combine Monthly Sales Exports into One Quarter”Step by step: Python: Combine Monthly Sales Exports into One Quarter
All 11 steps of the interactive module, in order. In the module you watch each one, then do it yourself in a practice copy that checks your work.
1. Three monthly exports
- July's export. Start a new Colab notebook as in module 1 and run import pandas as pd. In the new cell, type July's orders as a small table (in real life this line is pd.read_csv('july.csv')).
In a new notebook with pandas loaded, type July's orders as a small table.
- August's export. Press Enter and type August.
Then August.
- September's export. And September.
2. Stack them
- Label each month. Press Shift+Enter to run the cell. In the new cell below, give each table a month column, so you can still tell the months apart once they are stacked.
Run the cell with Shift Enter. In the new cell, give each table a month column, so you can tell them apart later.
- Run it. Press Shift+Enter: Colab runs the cell and opens a new empty cell below. (In the practice, click the run button ▶ at the left of the cell.)
Run it.
- Stack the three months. pd.concat stacks tables under each other, like pasting three exports into one sheet but without the repeated headers. ignore_index=True numbers the rows 0 to 5 again.
pd concat stacks the three tables into one, with no repeated headers. Then show it.
- Run it. Press Shift+Enter: Colab runs the cell and opens a new empty cell below. (In the practice, click the run button ▶ at the left of the cell.)
Run it.
3. Totals by month and customer
- Total each month. Six orders in one table, each with its month. Total by month; sort=False keeps July, August, September in the order they appear instead of A to Z.
Six orders in one table. Now total each month, in the order they appear.
- Run it. Press Shift+Enter: Colab runs the cell and opens a new empty cell below. (In the practice, click the run button ▶ at the left of the cell.)
Run it.
- Total each customer. July $2,110, August $2,950, September $2,870. Now the same quarter by customer.
Now the same quarter, by customer.
- Run it. Press Shift+Enter: Colab runs the cell and opens a new empty cell below. (In the practice, click the run button ▶ at the left of the cell.)
Run it.
Screenshots
![The month labels july['month'] = 'Jul', 'Aug' and 'Sep' typed in the next cell](/content/img/python-combine-exports/05-labels.webp)
![quarter = pd.concat([july, august, september], ignore_index=True) typed](/content/img/python-combine-exports/07-concat.webp)
![quarter.groupby('month', sort=False)['amount'].sum() typed](/content/img/python-combine-exports/09-month.webp)
![quarter.groupby('customer')['amount'].sum() typed](/content/img/python-combine-exports/11-cust.webp)
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