The while loop, as was the case with the if statement, supports an optional else clause containing a block of program statements executed when the expression is False.

while循环与if语句一样，支持一个可选的else子句，其中包含一个当表达式计算为False时执行的程序语句块。

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For a while loop, however, this means the code in the else clause is executed once, after the loop is terminated (see the pseudocode shown in Listing 7).

但是对于while循环，这意味着在循环终止后，else子句中的代码被执行一次(参见清单7中的伪代码)。

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The expression used in the if statement (and in the elif clause and the while loop discussed later in this article) can be as complex as necessary.

if语句(以及本文后面讨论的elif子句和while循环)中的表达式可以很复杂。

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