Python Refactoring: 'while True' Infinite Loops & The 'input' Function

In this video I'm refactoring some Python code that a reader sent me over Twitter and asked me to make it more Pythonic. It features reading user input from the command-line with Python's built-in "input()" function. The program runs an infinite "while" loop until the user enters either "yes" or "no". I'm taking this example through a couple of refactorings to remove code duplication and to make it more resilient to bad user input.

The refactored solution features a (still infinite) "while True:" loop and removes the duplicated lines of code to make the function more maintainable. It's funny how sometimes even a function that's just a few lines long in Python can be cleaned up and refactored further so that it's more resilient and robust.

What we end up here is the Python equivalent of a "do while" loop in other programming languages. A native "Python do while" doesn't exist, but I think this solution is fairly close and just as readable.

Watch the full video to see how you can remove extra spaces and other whitespace characters from a Python string. You'll also learn some other techniques for normalizing user input, like converting the user input string to lowercase first with Python's "lower()" method.

This video also features "Thonny", a cute little Python development environment that features a debugger you can use to visualize the execution of your Python programs. Hopefully that makes it easier for you to follow along with the code examples I give in the video. Leave a comment below if you found it helpful.

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[bensmith]

I like the concept of this video.
i.e. Talking through simple code & refactoring
More please.

[lucassilvas]

You can simplify it a little bit more by using a walrus operator from 3.8.0 as well:
def get_answer(prompt):
while (answer := not in ("yes", "no"):
continue
return answer

[aztrodj]

Finally... i get the solution to this simple yes/no issue. you just got all my doubts!

[swellsca]

Dan, question? This function only works if the prompt is 'yes or no'. Can it be made more general - say if the prompt is 'Enter Seat number' and we want to make sure the seat num entered is a digit, or 'Enter seat' might be 'N14'? can we add multiple if statement? depending on the prompt?
Thanks for your tips and videos - big help for early python converter, steve

[inktex]

Thanks! Im joining my robotics team in my school so I was looking for coding channels and i found you! Super helpful and clear 👌👌👍

[MarsLanding]

Awesome video, explained exactly what I was struggling with. Thank you!

[wongkk]

Can we replace the code 'return' with code 'break'? What difference does it make?

[heshankumarasinghe]

I am a beginner and I have never thought of using the str.strip method when getting input. Thank you....

[saroons]

Can u help me out .. iam currently working on gaia data with python ..
There iam dealing with fits file containing large data of 6M rows and 31 columns .. i need to bin the data according to some conditions that i need to apply to two of the coloumns .. and bin the entire data according to that .. and store data in each bin (like a box) in seperate fits files. Can you help me out

[julius]

Can i get any key input without stop the while loop and without install an module? Sorry for my bad englisch im a german😂

[zomaarwat]

So is while-True-return or while-True-break the general pythonic answer to do-while?

[emekaonah]

I love your concepts, it's just so wonderful. I tried to use the .split() and .lower() concept on a short code having to do with lists. I know .lower() doesn't work with lists, but is there away I can go about this, please? I will appreciate a solution. Thanks.

store = list()

while True:
user_input = input("Enter something: ")
grouper = store.append(user_input)
if user_input == ("ok").split().lower():
break
print(store)

[srikanthbadampudi]

sir what python Ide you are using can you mention what....

[ashifkasala]

Thanks for giving this video it saved me....as it is a day before exam preparation

[neofit]

very cool about strip() and lower(), simple and useful, thanks, Dan!

[otherleader]

can anyone explain why it prints yes or no depending whatever you answer with

[phormynx]

What's the deal with the italicized font suddenly materializing? Is that a "Thonny" thing?

[humanrays]

I prefer this approach but I've seen some people say it's best to make sure the exit condition is clear from the while statement.

[MaxHolzapfel]

For membership checking I normally like to work with sets. They have some handy features like being able to subtract on set from the other or issubset().

[chinmaykulkarni]

I like the video a lot can u explain how we write this in Python - while(true);//this is from C to tell that stay in the loop I.e do nothing while condition is true