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 nin 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')
numbers= [1,2,3,4,5]
for nin 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 thefor loop doesnot end withbreak the index0 valueis 1 the index1 valueis 2 the index2 valueis 3 the index3 valueis 4 the loop doesnot end withbreak
