python学习笔记3-循环1

1 while break continue

 #while语句
 '''
 while 判断条件：
     执行语句……
 '''
 count = 0
 while (count < 9):
    print ('The count is:', count)
    count = count + 1
 
 print ("Good bye!")
 
 # continue 和 break 用法
 
 i = 1
 while i < 10:
     i += 1
     if i%2 > 0:     # 非双数时跳过输出
         continue
     print (i)         # 输出双数2、4、6、8、10
 
 i = 1
 while 1:            # 循环条件为1必定成立
     print (i)         # 输出1~10
     i += 1
     if i > 10:     # 当i大于10时跳出循环
         break
 
 #死循环
 '''
 var = 1
 while var == 1 :  # 该条件永远为true，循环将无限执行下去
    num = raw_input("Enter a number  :")
    print "You entered: ", num
 
 print "Good bye!"
 '''
 
 #while … else
 count = 0
 while count < 5:
    print (count, " is  less than 5")
    count = count + 1
 else:
    print (count, " is not less than 5")
 
 #简单语句组
 flag = 1
 while (flag): print ('Given flag is really true!');flag=0;
 print ("Good bye!")

1.1 break continue pass

 #break语句
 for letter in 'Python':     # First Example
    if letter == 'h':
       break
    print ('Current Letter :', letter)
 
 var = 10                    # Second Example
 while var > 0:
    print ('Current variable value :', var)
    var = var -1
    if var == 5:
       break
 
 print ("Good bye!")
 
 #continue语句
 for letter in 'Python':     # 第一个实例
    if letter == 'h':
       continue
    print ('当前字母 :', letter)
 
 var = 10                    # 第二个实例
 while var > 0:
    var = var -1
    if var == 5:
       continue
    print ('当前变量值 :', var)
 print ("Good bye!")
 
 #pass语句
 # 输出 Python 的每个字母
 for letter in 'Python':
    if letter == 'h':
       pass
       print ('这是 pass 块')
    print ('当前字母 :', letter)
 
 print ("Good bye!")

2 for

 #for语句
 '''
 for iterating_var in sequence:
    statements(s)
 '''
 for letter in 'Python':     # 第一个实例
    print ('当前字母 :', letter)
 
 fruits = ['banana', 'apple',  'mango']
 for fruit in fruits:        # 第二个实例
    print ('当前水果 :', fruit)
 
 print ("Good bye!")

2.1 序列索引迭代

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