预习:
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while、标志、break、continue、
知识点:
7.2 while 循环简介
while循环:不断的运行,直到条件不满足为止;
7.2.1 使用while循环
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7.2.2 让用户选择何时退出
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7.2.3 使用标志
标志:判断整个程序是否处于活动状态;变量叫标志;要求很多条件都满足才继续运行的程序中,可定义一个变量;
(为True时继续运行,为False时停止运行)
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7.2.4 使用break退出循环
break:立即退出while循环;(不再运行余下的代码)
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7.2.5 在循环中使用continue
continue:返回到循环开头,根据条件测试结果决定是否继续执行循环;
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7.2.6 避免无限循环
while循环必须有停止运行的途径,这样才不会没完没了的执行下去;
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练习:
大大:
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我的图:
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