thank you so much for explaining it !

There's a difference between the normal if: else: statement in Python and this. This is specifically what is called a "ternary operator", and it's a different syntax for a different operation (although it does similar things.

https://www.geeksforgeeks.org/ternary-operator-in-python/

It's a bit of a shame that Python uses the same tokens if and else for both the conditional statement and the ternary operator - most languages don't, and it does make it confusing.

i dont understand how you can write a whole line with if AND else without any ':' and it works. everytime i try to do something like that i get an error. does someone has an idea of why that is please ?

calling twice sqrt is not a very fast way, smaller programms not always better