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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.

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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.

nathank on Dec. 12, 2020

I thought I knew repr very well but this just adds an additional level of depth. Thanks Dan!

dbristow31 on Jan. 28, 2021

This has been helpful. I made a note to myself to include a repr method to all of my classes, moving forward.

jeffersongarciaor on Jan. 29, 2021

Just amazing to learn new stuffs. Thank you Dan for this tutorial.

shangcode on Feb. 20, 2021

Learned a lot! 😀

Cavalcante on March 18, 2021

That’s Gold! I have seen this use of __ str__ in django when you use the admin interface, but I did not know it worked undercover.

Thanks for the lesson.

amirrastkhadiv on April 7, 2021

That’s informative. Thanks Dan!

Espius Edwards on Sept. 3, 2021

Thank you for your concise tutorial!

François 江戸 D on Sept. 21, 2021

No sooner said than used, my last piece of code got cleaner :)

MakerMike369 on March 7, 2022

Was looking for info for making a “Class template” of sorts. .__repr__() fits the bill nicely!

mckown on June 30, 2022

Excellent presentation! I learned quite a bit. Thanks!

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