The assert() statement is a convenient mechanism for incorporating diagnostic tests in code. Expressions used with the standard assert statement should not have side effects. Typically, the behavior of the assert statement depends on the status of a runtime property. If defined, the assert statement is defined to evaluate its expression argument and throw an exception AssertionError if the result of the expression is convertible to false. If undefined, assert is defined to be a no-op. Consequently, any side effects resulting from evaluation of the expression in the assertion are lost in non-debugging versions of the code.
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