python学习笔记3-循环1

1 while break continue

 1 #while语句
 2 '''
 3 while 判断条件：
 4     执行语句……
 5 '''
 6 count = 0
 7 while (count < 9):
 8    print ('The count is:', count)
 9    count = count + 1
10 
11 print ("Good bye!")
12 
13 # continue 和 break 用法
14 
15 i = 1
16 while i < 10:   
17     i += 1
18     if i%2 > 0:     # 非双数时跳过输出
19         continue
20     print (i)         # 输出双数2、4、6、8、10
21 
22 i = 1
23 while 1:            # 循环条件为1必定成立
24     print (i)         # 输出1~10
25     i += 1
26     if i > 10:     # 当i大于10时跳出循环
27         break
28 
29 #死循环
30 '''
31 var = 1
32 while var == 1 :  # 该条件永远为true，循环将无限执行下去
33    num = raw_input("Enter a number  :")
34    print "You entered: ", num
35 
36 print "Good bye!"
37 '''
38 
39 
40 #while … else 
41 count = 0
42 while count < 5:
43    print (count, " is  less than 5")
44    count = count + 1
45 else:
46    print (count, " is not less than 5")
47 
48 #简单语句组
49 flag = 1
50 while (flag): print ('Given flag is really true!');flag=0;
51 print ("Good bye!")

1.1 break continue pass

 1 #break语句
 2 for letter in 'Python':     # First Example
 3    if letter == 'h':
 4       break
 5    print ('Current Letter :', letter)
 6   
 7 var = 10                    # Second Example
 8 while var > 0:              
 9    print ('Current variable value :', var)
10    var = var -1
11    if var == 5:
12       break
13 
14 print ("Good bye!")
15 
16 #continue语句
17 for letter in 'Python':     # 第一个实例
18    if letter == 'h':
19       continue
20    print ('当前字母 :', letter)
21 
22 var = 10                    # 第二个实例
23 while var > 0:              
24    var = var -1
25    if var == 5:
26       continue
27    print ('当前变量值 :', var)
28 print ("Good bye!")
29 
30 #pass语句
31 # 输出 Python 的每个字母
32 for letter in 'Python':
33    if letter == 'h':
34       pass
35       print ('这是 pass 块')
36    print ('当前字母 :', letter)
37 
38 print ("Good bye!")

2 for

 1 #for语句
 2 '''
 3 for iterating_var in sequence:
 4    statements(s)
 5 '''
 6 for letter in 'Python':     # 第一个实例
 7    print ('当前字母 :', letter)
 8 
 9 fruits = ['banana', 'apple',  'mango']
10 for fruit in fruits:        # 第二个实例
11    print ('当前水果 :', fruit)
12 
13 print ("Good bye!")

2.1 序列索引迭代

 1 #序列索引迭代
 2 fruits = ['banana', 'apple',  'mango']
 3 for index in range(len(fruits)):
 4    print ('当前水果 :', fruits[index])
 5 
 6 print ("Good bye!")
 7 
 8 #for...else
 9 for num in range(10,20):  # 迭代 10 到 20 之间的数字
10    for i in range(2,num): # 根据因子迭代
11       if num%i == 0:      # 确定第一个因子
12          j=num/i          # 计算第二个因子
13          print ('%d 等于 %d * %d' % (num,i,j))
14          break            # 跳出当前循环
15    else:                  # 循环的 else 部分
16       print (num, '是一个质数')