How do “and” and “or” work when combined in one statement?

Question

For some reason this function confused me:

def protocol(port):
    return port == \"443\" and \"https://\" or \"http://\"

Can somebody expl

Answer 1

This is an ugly hack that is not recommended. It works because of the short-circuiting behaviour of and and or and that they return the one of their arguments rather than a boolean value. Using this technique gives a risk of introducing hard-to-find bugs, so don't use it in new code.

Here's an example of how the and/or idiom can give an unexpected result:

>>> foo = 'foobar'
>>> bar = 'foobar'
>>> x = 0
>>> y = 1
>>> (foo == bar) and x or y   # Will this return the value of x if (foo == bar)?
1

Prefer instead the newer notation:

return "https://" if port == "443" else "http://"