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Python Build a Social Network with Flask Takin' Names LoginManager

Posted by T K
T K
21,479 Points

The comma in order_by = ('joined_at',)

Hi everyone,

So after this video, I decided to run my app.py just to make sure the tables and user was being created and there were no bugs.

After I cleared up the inevitable typos I kept getting KeyErrors.

I checked and double checked my code but couldn't work out why an error was being throw. Thankfully a quick google lead me to the comma missing from ('joined_at',).

What's the deal? Why does that throw a KeyError?

Thanks guys,

Tayler

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

It is context specific, but some objects want a container of things instead of a single object. Many times a tuple is used as the preferred container. In the case of passing a single item in a container, a comma is needed to indicate the parens represent a container and not just grouped code, for example a line continuation.

T K
T K
21,479 Points

Hi Chris, thanks for getting back to me.

I think I understand. So Flask is looking for a container with 2+ items, and when it can only find one it throws an error, so adding a comma sort of tricks it into thinking there's another item there.

It's seems confusing in this case seeing as you can surely only "order_by" one thing!