如何使用遞歸選擇字符串中的特定部分？

Question

所以我用遞歸工作，

的問題是：到目前爲止"(43)"

我的代碼：

" Good(43) Morning"

我必須用遞歸來打印所有的信息在括號內是這樣是：

def extractor(myString): 
    if len(myString) == 0: 
     return "" 



    if myString[0] == "(": 
     return myString[0] 
    if myString[0] == ")": 
     return myString[:] 
    else: 
     return extractor(myString[1:]) 

我只能得到括號。我怎麼能改變它？

Answer 1

就快：

def extractor(myString): 
    if not myString: # empty strings are falsy 
     return "" 
    if myString[0] == "(": 
     if myString[-1] == ")": # success 
      return myString 
     else: # only starts with (, trim from the end 
      return extractor(myString[:-1]) 
    else: # doesn't start with (, trim from beginning 
     return extractor(myString[1:]) 

Answer 2

如果你有興趣，這裏是你的代碼的迭代版本。 :)

def iterative_extractor(mystring): 
    if not mystring: 
     return "" 

    while mystring[0] != "(" or mystring[-1] != ")": 
     if mystring[0] != "(": 
      mystring = mystring[1:] 
     else: 
      mystring = mystring[:-1] 
    return mystring 

OR：

def iterative_extractor(mystring): 
    if not mystring: 
     return "" 

    while mystring[0] != "(": 
     mystring = mystring[1:] 

    while mystring[-1] != ")": 
     mystring = mystring[:-1] 

    return mystring 

輸出：

mystring = "Lol (234) mate!" 
print(iterative_extractor(mystring)) 
>>> "(234)"