初学python几天，两个函数的题目应该怎么实现？

def repeat_letter(words, char_positions, repl_times):
    """ (list of str, list of int, int) -> NoneType

    Precondition: (len(words) == len(char_positions)) and (repl_times > 0)

    Modify every word in words by replicating the character
    at index specified by the corresponding element in char_positions
    repl_times additional times. If the index specified in char_positions is not
    valid, leave the word unchanged.

    >>> words = ['hello', 'exercise', 'with', 'words']
    >>> repeat_letter(words, [4, 2, 10, -2], 3)
    >>> words
    ['helloooo', 'exeeeercise', 'with', 'wordddds']
    """

def sum_numbers(s):
    """ (str) -> int

    Preconditions:
    - s is not the empty string
    - s contains only non-negative integers seperated by a single space.
    - the first character of s is not a space; neither is the last one.

    Return the sum of all the integers in s.

    # Requirements: Do NOT use lists. You must use a for loop.

    >>> sum_numbers('45')
    45
    >>> sum_numbers('34 3 542 11')
    590
    """

自己研究出来了   



def repeat_letter(words, char_positions, repl_times):
    if len(words) != len(char_positions):
        print('Error:len(words) != len(char_positions)!')
        return
    if repl_times <= 0:
        print('Error:repl_times <= 0!')
        return
    i = 0
    while i < len(words):   
        if len(words[i]) > abs(char_positions[i]):
            words[i] = words[i][0:char_positions[i]]+words[i][char_positions[i]]*repl_times+words[i][char_positions[i]:]
        else:
            words[i] = words[i]        
        i += 1


words = ['hello', 'exercise', 'with', 'words']
print("old words: %s" % words)
repl_times = 3
char_positions = [4, 2, 10, -2]
repeat_letter(words, char_positions, repl_times)
print("new words: %s" % words)

words = ['hello', 'exercise', 'with', 'words']
print("old words: %s" % words)
repl_times = 3
char_positions = [5, 8, 4, 5]
repeat_letter(words, char_positions, repl_times)
print("new words: %s" % words)

1. def repeat_letter(words,char_positions,repl_times):
   
2.     """ (list of str, list of int, int) -> NoneType
   
3. 
   
4.     Precondition: (len(words) == len(char_positions)) and (repl_times > 0) """
   
5.    
   
6.     for key,value in enumerate(words):        
   
7.         p = char_positions[key]
   
8.         if p<len(value):            
   
9.             words[key] = value[:p]+value[p]*repl_times+value[p:]
   
10. 
    
11. 
    
12. def sum_numbers(s):
    
13.     """ (str) -> int
    
14. 
    
15.     Preconditions:
    
16.     - s is not the empty string
    
17.     - s contains only non-negative integers seperated by a single space.
    
18.     - the first character of s is not a space; neither is the last one.
    
19. 
    
20.     Return the sum of all the integers in s.
    
21. 
    
22.     # Requirements: Do NOT use lists. You must use a for loop."""
    
23.     numbers = s.split(' ')
    
24.     n_sum = 0
    
25.     for n in numbers:
    
26.         n_sum = n_sum + int(n)
    
27. 
    
28.     return n_sum

复制代码

zhnglicho 发表于 2017-10-19 13:48

高手写的果然很精炼！谢谢！