Complex Logical Operations

The parts of an expression containing AND or OR operators are evaluated only until it’s known whether the condition is true or false. Thus, evaluation of the expression

sex == "M" AND age >= 65

stops immediately if sex is not equal to "M" (i.e., at that point, it’s certain that the entire expression is false) and continues if gender is equal to "M" (i.e., the entire expression could still be true if the condition age >= 65 is true). This feature of conditional AND and conditional OR expressions is called short-circuit evaluation.