54 lines
1.6 KiB
Markdown
54 lines
1.6 KiB
Markdown
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---
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title: While Loop Statements
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localeTitle: 循环语句
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---
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## 循环语句
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Python使用`while`循环与其他流行语言类似。 `while`循环计算条件，然后在条件为真时执行代码块。代码块重复执行，直到条件变为false。
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基本语法是：
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```python
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counter = 0
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while counter < 10:
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# Execute the block of code here as
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# long as counter is less than 10
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```
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一个例子如下所示：
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```python
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days = 0
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week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
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while days < 7:
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print("Today is " + week[days])
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days += 1
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```
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输出：
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```
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Today is Monday
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Today is Tuesday
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Today is Wednesday
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Today is Thursday
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Today is Friday
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Today is Saturday
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Today is Sunday
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```
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逐行解释上述代码：
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1. 变量'days'设置为值0。
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2. 将变量周分配给包含一周中所有日期的列表。
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3. while循环开始
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4. 代码块将被执行，直到条件返回'true'。
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5. 条件是'days <7'，其中rougly说运行while循环直到变量天数小于7
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6. 所以当days = 7时，while循环停止执行。
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7. days变量在每次迭代时都会更新。
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8. 当while循环第一次运行时，“Today is Monday”行被打印到控制台上，变量days变为等于1。
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9. 由于变量天数等于1，小于7，因此再次执行while循环。
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10. 它一次又一次地进行，当控制台打印出“今天是星期天”时，变量天数现在等于7，而while循环停止执行。
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#### 更多信息：
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* [Python `while`语句文档](https://docs.python.org/3/reference/compound_stmts.html#the-while-statement)
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