众多语言中都有if else这对条件选择组合，但是在python中还有更多else使用的地方，比如说循环for，或者while都可以和else组合。
下面简单介绍一下for-else while-else组合
循环组合中的else执行的情况下是循环正常结束（即不是使用break退出）。如下列代码：
numbers = [1,2,3,4,5]
for n in numbers:
if (n > 5):
print('the value is %d '%(n))
break
else:
print('the for loop does not end with break')
i = 0
while(numbers[i] < 5):
print('the index %d value is %d'%(i, numbers[i]))
if (numbers[i] < 0) :
break
i = i + 1
else:
print('the loop does not end with break')
执行结果如下：
C:\Python27>python.exe for_else.py
the for loop does not end with break
the index 0 value is 1
the index 1 value is 2
the index 2 value is 3
the index 3 value is 4
the loop does not end with break
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