think python学习心得-（5）迭代与字符串的使用

for while return break等语句，用法同C语言很像。

  

   

    

     

    
    

     

      m=5.0
     
    
   

    

     

    
    

     

      def sqr(a):
     
    
   

    

     

    
    

     

       x=a
     
    
   

    

     

    
    

     

       y=(x+m/x)/2
     
    
   

    

     

    
    

     
 if abs(y-x)<0.00001:
     
    
   

    

     

    
    

     
 print y 
     
    
   

    

     

    
    

     
 else:
     
    
   

    

     

    
    

     

       sqr(y)
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      def sq(a):
     
    
   

    

     

    
    

     

       x=a
     
    
   

    

     

    
    

     

       y=(x+m/x)/2
     
    
   

    

     

    
    

     

       flag= abs(y-x)
     
    
   

    

     

    
    

     
 if flag < 0.00001:
     
    
   

    

     

    
    

     
 return y 
     
    
   

    

     

    
    

     
 else:
     
    
   

    

     

    
    

     

       sqr(y)
     
    
   

    

     

    
    

     

      sq(m) 
     
    
  
 

  

   

    

     

    
    

     

      import math
     
    
   

    

     

    
    

     

      def sqr(a):
     
    
   

    

     

    
    

     

       x=a
     
    
   

    

     

    
    

     

       y=(x+m/x)/2
     
    
   

    

     

    
    

     
 if abs(y-x)<0.00001:
     
    
   

    

     

    
    

     
 print y
     
    
   

    

     

    
    

     
 return y
     
    
   

    

     

    
    

     
 else:
     
    
   

    

     

    
    

     

       sqr(y)
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      def sq(a):
     
    
   

    

     

    
    

     

       x=a
     
    
   

    

     

    
    

     

       y=(x+m/x)/2
     
    
   

    

     

    
    

     

       flag= abs(y-x)
     
    
   

    

     

    
    

     
 if flag < 0.00001:
     
    
   

    

     

    
    

     
 return y 
     
    
   

    

     

    
    

     
 else:
     
    
   

    

     

    
    

     

       sqr(y)
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      for i in range(9):
     
    
   

    

     

    
    

     

       j=float(i+1)
     
    
   

    

     

    
    

     

       m=j
     
    
   

    

     

    
    

     
 print j,math.sqrt(j),sq(j)
     
    
  
 

  

   

    

     

    
    

     

      import math
     
    
   

    

     

    
    

     

      def eval_loop():
     
    
   

    

     

    
    

     
 while True:
     
    
   

    

     

    
    

     

       line = raw_input('>')
     
    
   

    

     

    
    

     
 if line == 'done':
     
    
   

    

     

    
    

     
 break
     
    
   

    

     

    
    

     
 print eval(line)
     
    
   

    

     

    
    

     

       eval_loop()
     
    
   

    

     

    
    

     
 print 'Done!'
     
    
   

    

     

    
    

     

      eval_loop()
     
    
  
 

略。

8.字符串

练习8-1

  

   

    

     

    
    

     

      word='fruit'
     
    
   

    

     

    
    

     

      length=len(word)
     
    
   

    

     

    
    

     

      for i in range(length):
     
    
   

    

     

    
    

     
 print word[length-i-1]
     
    
  
 

  

   

    

     

    
    

     

      prefixs='JKLMNP'
     
    
   

    

     

    
    

     

      suffix = 'ack'
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      for letter in prefixs:
     
    
   

    

     

    
    

     
 print letter+suffix
     
    
  
 

表示fruit中的全体字符

练习8-4

  

   

    

     

    
    

     

      def find(word,letter,i):
     
    
   

    

     

    
    

     

       index = i
     
    
   

    

     

    
    

     
 while index < len(word):
     
    
   

    

     

    
    

     
 if word[index]==letter:
     
    
   

    

     

    
    

     
 return index
     
    
   

    

     

    
    

     

       index = index+1
     
    
   

    

     

    
    

     
 return -1
     
    
   

    

     

    
    

     

      print find('Hellowordthisiszhangchangle!','s',2)
     
    
  
 

  

   

    

     

    
    

     

      def count(word,letter):
     
    
   

    

     

    
    

     

       count1 = 0
     
    
   

    

     

    
    

     

       length = len(word)
     
    
   

    

     

    
    

     
 for i in range (length):
     
    
   

    

     

    
    

     
 if word[i] == letter:
     
    
   

    

     

    
    

     

       count1=count1+1
     
    
   

    

     

    
    

     
 return count1
     
    
   

    

     

    
    

     

      print ('Please input a world and a letter to be counted')
     
    
   

    

     

    
    

     

      word1=raw_input('>')
     
    
   

    

     

    
    

     

      letter1=raw_input('>>')
     
    
   

    

     

    
    

     

      print count(word1,letter1)
     
    
  
 

  

   

    

     

    
    

     

      word='banana'
     
    
   

    

     

    
    

     

      index=word.count('a')
     
    
   

    

     

    
    

     

      print index
     
    
  
 

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原文链接：zclhit.blog.csdn.net/article/details/50988194