Also, the && bit is an example of short-circuit logical expression evaluation, which is a fairly standard feature of most languages. Since "false AND anything" is always False, the right-hand side of the expression won't be evaluated at all if the left-hand side is determined to be false. (It, so to speak, instead "takes the short circuit.") The programmer is using this to avoid referencing a property of something that is in a hash if that thing isn't in the hash, thus avoiding a runtime error.