What does "|" sign mean in a Django template?
It's a bitwise "or".  It means escape if the property doesn't exist/is null.
I often see something like that:
something.property|escape

something is an object, property is it's string property. escape - i don't know :)

What does this mean? And what min python version it is used in?

EDIT: The question was asked wrongly, it said "What does | mean in Python", so the bitwise or answers are correct, but irrelevant, please do not downvote them