request.endpoint[:5] 的内容

Question

I'm going through Miguel Grinbergs Flask book and at one point he uses the following line:

request.endpoint[:5] != 'auth.'

I know [:5] is a slice operation, but I'm not sure why it is being used here. What does the list consist of that we only want elements 0-5?

Answer 1

What does the list consist of that we only want elements 0-5?

To be precise, request.endpoint is not a list, it's a string. And it doesn't matter what the rest of it contains, the code is only concerned with it beginning with 'auth.' :

('auth.somethingsomething'[:5] == 'auth.') is True

request.endpoint is the name the current view function was registered as, for example auth.login is the name of the def login(): view. Views that have a prefix like prefix. were registered on a blueprint, which groups related views. So the code is checking if the current view being handled is part of the auth blueprint.

If you're curious about what value it contains, you can add a debugging breakpoint to the code and inspect it:

# ... previous app code ...
import pdb; pdb.set_trace()
request.endpoint[:5] != 'auth.'

Then run and test the code. When it hits that point, it'll pause execution and give you a pdb shell, which will let you look at the request object and its endpoint attribute.

Answer 2

you can checking on terminal by

venv $ python manage.py shell
import flask from request
print(request.endpoint)