你所不知道的python循环中的else

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