使用递归/将“无”附加到我的输出

Question

出于某种原因，我似乎无法正确地返回东西。 我正在尝试使用递归使字符串成为首字母缩略词（请忽略我的代码草率，哈哈）但它只是将 None 附加到我想要的输出的末尾！

我怎样才能解决这个问题？ 同样，这个问题需要递归！

def recAbbrev(lst):
    'return a single string with the first character of all the strings in a list combined and capitalized.'
    if len(lst)== [] :
        return 0
    
    if len(lst)>0:
        if type(lst[0])==list:
            return 1 + recAbbrev(lst[0])
        else:
            acronym = ""
            letter = ""
            letter = letter + lst[0][:1]
            letter = letter.upper()
            acronym = acronym + letter
            print(acronym, end = '')  
            return recAbbrev(lst[1:])
           

输出

Traceback (most recent call last):
  File "C:\Users\17734\OneDrive\Desktop\fall 2021\csc242\homework\csc242hw7-s.py", line 80, in <module>
    print(recEvenNumbers(['c','a','t',' ' ,0,'h',1,'a',2,'t',100]))
  File "C:\Users\17734\OneDrive\Desktop\fall 2021\csc242\homework\csc242hw7-.py", line 49, in recEvenNumbers
    return recEvenNumbers(lst[1:])
  File "C:\Users\17734\OneDrive\Desktop\fall 2021\csc242\homework\csc242hw7-s.py", line 49, in recEvenNumbers
    return recEvenNumbers(lst[1:])
  File "C:\Users\17734\OneDrive\Desktop\fall 2021\csc242\homework\csc242hw7-As.py", line 49, in recEvenNumbers
    return recEvenNumbers(lst[1:])
  [Previous line repeated 1 more time]
  File "C:\Users\17734\OneDrive\Desktop\fall 2021\csc242\homework\csc242hw7-s.py", line 47, in recEvenNumbers
    return recEvenNumbers(evens)
  File "C:\Users\17734\OneDrive\Desktop\fall 2021\csc242\homework\csc242hw7-.py", line 44, in recEvenNumbers
    elif type(lst[0]) == int:
TypeError: 'int' object is not subscriptable

启动 recAbbrev 无 CPUNone RAMNone 启动 recEvenNumbers

thank you!

Answer 1

len返回一个int而你不想返回 0

    if len(lst)== 0:
        return ''