A Professional’s Tutorial to Python If + While Loop

Control flow, a fundamental Python term and concept

Adam Ross Nelson
6 min readSep 17, 2023


For an overview of these tutorials, click here (or click the image).

Welcome to forth, in a series of tutorials that teach beginner Python specifically for aspiring data scientists. For an overview of these tutorials, click here.


Imagine planning a shopping trip to your favorite supermarket. Every aisle and shelf represents potential decisions. With a well-prepared shopping list, you have a clear plan: pick up some tomatoes, then bread, followed by milk.

However, when you reach the dairy section, you find that your preferred brand of milk is out of stock. Now, you have to make a decision on the spot: choose another brand, skip the milk, or maybe check another store.

In programming, particularly in Python, flow control works much like this shopping scenario. Using statements like if and while, your code can make decisions (“make decisions”) on the fly. The code can adjust to different conditions, and ensure that your program’s “shopping trip” is both efficient and adaptable to unexpected scenarios.

Side note: Don’t forget the fruit loops! 🥣

Understanding how to control the flow of your code while it’s running is akin to making your shopping trip as efficient as possible. It lets you save time, energy, and resources for a trip to the park with the kids and family.

Fruit loop children’s cereal. A very close up image.
Image Credit: Author’s illustration created in Canva.com.

Your code need not be linear. Mastering control flow principles — embodied by constructs like if statements and while loops—will liberate you. It's through these mechanisms that the door to complexity swings wide open, where algorithms breathe and adapt, and where procedures become more than just static lists of instructions. They become dynamic, reactive, and intelligent.


For those professionals who have a firm grasp of data but are new to Python, understanding its control flow mechanisms, such as the if statement and the while loop, can be pivotal. This tutorial explores these constructs in detail, with…



Adam Ross Nelson

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