A common situation: checking that the variable is within the given limits. You could use the logical operator and:

if x> = 5 and x <20:

However, Python provides us with a syntactic convenience that looks more "mathematical." Such a record is both shorter and more understandable:

As a comparison operators in chains, any of the list in any combinations can be:

"<", "==", "> =", "<=", "! =", "is" ["not"], ["not"] "in"

Those. The recording of the type A C is quite legal, although it is difficult to understand.