Python: reverse string

　　

 

1. ''.join(reversed('abcd'))

    

2. 切片

   p[::-1]
   
   p[-1::-1]
   
   p[-1:-(len(p)+1:-1]

    

3. from functools import reduce
   
   b = 'rty'
   
   print(reduce(lambda prev, curr: curr + prev, b))
   print(reduce(lambda prev, curr: curr + prev, b, '!'))

    

4. recursion
   

   b = 'rtyu'
   
   
   def bud(s: str):
       if len(s) == 1:
           return s
       return bud(s[1:]) + s[0]
   
   
   print(bud(b))

    

5. simulate stack
   

   b = 'rtyu'
   
   
   def bud(s: str):
       vale = list(s)
       ret = ''
       while vale:
           ret += vale.pop(-1)
       return ret
   
   
   print(bud(b))

    

6. exploit circulate
   

   b = 'rtyu'
   
   
   def bud(s: str):
       era = ''
   
       # 0 1 .. len(s)-1
       # for p in range(len(s)):
       #     era += s[-p - 1]
       #     era += s[len(s) - 1 - p]
       
       # len(s)-1 ... 1 0
       # for p in range(len(s) - 1, -1, -1):
       #     era += s[p]
       
       for i, _ in enumerate(s):
           era += s[len(s) - 1 - i]
           
       return era
   
   
   print(bud(b))

    

7. b = 'rtyu'
   
   print(b[slice(-1, -(len(b) + 1), -1)])