Python：循环语句

while

在某种条件下，执行某段程序

>>> w=0
>>> while w<5:
...     print 'w :',w
...     w=w+1
... 
w : 0
w : 1
w : 2
w : 3
w : 4

continue

跳过位于之后的语句，开始下一轮循环

#输出10以内偶数
>>> c=1
>>> while c<10:
...     c+=1
...     if c%2>0:
...             continue
...     print c
... 
2
4
6
8
10

break

跳出循环

>>> b=1
>>> while 1:
...     print b
...     b+=1
...     if b>5:
...             break
... 
1
2
3
4
5

while..else

>>> e=1
>>> while e<5:
...     print e,'<5'
...     e+=1
... else:
...     print e,'=5'
... 
1 <5
2 <5
3 <5
4 <5
5 =5

for

可以遍历整个序列

>>> for f in 'hello':
...     print f
... 
h
e
l
l
o

索引

>>> singer=['adele','taylor','lana']
>>> for index in range(len(singer)):
...     print 'singer:',singer[index]
... 
singer: adele
singer: taylor
singer: lana

for..else

>>> for num in range(10,20):
...     for i in range(2,num):
...             if num%i==0:
...                     j=num/i
...                     print '%d=%d*%d'%(num,i,j)
...                     break
...     else:
...             print num,'is a prime number'
... 
10=2*5
11 is a prime number
12=2*6
13 is a prime number
14=2*7
15=3*5
16=2*8
17 is a prime number
18=2*9
19 is a prime number

嵌套

#输出100以内所有素数

#!/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, "is a prime number"
   i = i + 1

　　嵌套等价语句

#!/usr/bin/python
# -*- coding: UTF-8 -*-
for num in range(2,101):
     for i in range(2,num):
             if num%i==0:
                     j=num/i
                     break
     else:
             print num,'is a prime number'

 

#!/usr/bin/python
# -*- coding: UTF-8 -*-
import math
for i in range(50, 100 + 1):
    for j in range(2, int(math.sqrt(i)) + 1):   #比 i的开平方小的最大整数
        if i % j == 0:
            break
    else:
        print i,'is a prime number'

 

暂时这些，后续补充..