String Conversion for Python Containers (Lists, Dicts, …)

Pythonic OOP String Conversion: .__repr__() vs .__str__() Dan Bader 01:25

This is the final lesson in the course. In it, you’ll see how containers like lists and tuples convert their children to strings when called with str(). The lesson also encourages you to add a .__repr__() method to your classes.

Congratulations, you made it to the end of the course! What’s your #1 takeaway or favorite thing you learned? How are you going to put your newfound skills to use? Leave a comment in the discussion section and let us know.

00:00 Okay, so before we wrap this up, there’s one more thing I wanted to mention, and that is how containers convert their child objects—the objects they contain—to string.

00:12 Maybe the surprising thing is that even if you call str() on a container—so, I’m creating this list object here—even if you call str() on a container, it’s going to represent the internal objects with the .__repr__() function.

00:28 So when I—you know, I’m using the today object, which is just a datetime object—or, datetime.date object. So, when I have this list here of these three date objects and then I call str() on it, I actually get a string back that has the container with the .__repr__() inside.

00:45 So, this is just something to keep in mind how that works. If you wanted to convert those with the str() function individually, you would just need a loop or some kind of list comprehension to do that manually. But you know, that’s just a side note.

00:58 I think, really, the bottom line or the one takeaway from this thing here is # At least add a __repr__ to your classes :). All right! So, I hope you learned something new today and you’re going to be able to apply that in a real-world program or in some code that you write. Cool! Well, happy Pythoning, and I’ll talk to you soon.

michelnakhla on July 20, 2019

Very brief and nice.

paulakula11 on Aug. 28, 2019

concise and clear

Silver on Dec. 7, 2019

awesome!

Lokman on Feb. 27, 2020

Thanks @DanBader for best practice always provide __repr__ for classes. I guess dunder repr short form for represent.

sroux53 on June 5, 2020

Excellent!

Vaibhav Kumar on July 19, 2020

Very well crisp and concise.

avalidzy on July 23, 2020

Excellent voice delivery! The “dunder” use methodology is more apparent to me. Thanks Dan!

Idris Diba on Aug. 3, 2020

I learned a lot from this tutorial. Thank you Dan for your excellent method of teaching.

vikrant06 on Aug. 16, 2020

neat

Ghani on Oct. 7, 2020

Very good though very short!

cap-gnc on Oct. 9, 2020

Thank you. __str__ vs __repr__ demystified.

geultrin on Nov. 5, 2020

Thanks Dan. Short and sweet. I knew about dunder repr but did not understand it fully. I now see its usefulness

loopology on Nov. 29, 2020

This tutorial is from 2017 and it shows: It’s using “{}”.format() instead of the f”{}” string formatting.

What I miss about all RealPython tutorials: They should state their publication date up front as well as the Python version being used, and possibly what would need to be changed to be up to date.