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在Python的while循环中使用else以及循环嵌套的用法

Jun 10, 2016 pm 03:07 PM
python cycle

循环使用 else 语句
在 python 中,for … else 表示这样的意思,for 中的语句和普通的没有区别,else 中的语句会在循环正常执行完(即 for 不是通过 break 跳出而中断的)的情况下执行,while … else 也是一样。

#!/usr/bin/python

count = 0
while count < 5:
  print count, " is less than 5"
  count = count + 1
else:
  print count, " is not less than 5"

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以上实例输出结果为:

0 is less than 5
1 is less than 5
2 is less than 5
3 is less than 5
4 is less than 5
5 is not less than 5
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简单语句组
类似if语句的语法,如果你的while循环体中只有一条语句,你可以将该语句与while写在同一行中, 如下所示:

#!/usr/bin/python

flag = 1

while (flag): print 'Given flag is really true!'

print "Good bye!"

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注意:以上的无限循环你可以使用 CTRL+C 来中断循环。

Python 循环嵌套
Python 语言允许在一个循环体里面嵌入另一个循环。
Python for 循环嵌套语法:

for iterating_var in sequence:
 for iterating_var in sequence:
  statements(s)
 statements(s)
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Python while 循环嵌套语法:

while expression:
 while expression:
  statement(s)
 statement(s)
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你可以在循环体内嵌入其他的循环体,如在while循环中可以嵌入for循环, 反之,你可以在for循环中嵌入while循环。
实例:
以下实例使用了嵌套循环输出2~100之间的素数:#!/usr/bin/python

# -*- coding: UTF-8 -*-

i = 2
while(i < 100):
j = 2
while(j <= (i/j)):
if not(i%j): break
j = j + 1
if (j > i/j) : print i, " 是素数"
i = i + 1


print "Good bye!"

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以上实例输出结果:

2 是素数
3 是素数
5 是素数
7 是素数
11 是素数
13 是素数
17 是素数
19 是素数
23 是素数
29 是素数
31 是素数
37 是素数
41 是素数
43 是素数
47 是素数
53 是素数
59 是素数
61 是素数
67 是素数
71 是素数
73 是素数
79 是素数
83 是素数
89 是素数
97 是素数
Good bye!
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