运行以下代码时收到 python 语法错误

Question

Errors is thrown to verify if the character in a string is empty:

Python code

def first_and_last(message):
  if(message[0] ==  message[-1] or len(message[0])==0):
     return True
   return False
print(first_and_last("else"))
print(first_and_last("tree"))
print(first_and_last(""))

Error

Traceback (most recent call last):                                                                                            
  File "main.py", line 8, in <module>                                                                                         
    print(first_and_last(""))                                                                                                 
  File "main.py", line 2, in first_and_last                                                                                   
    if(message[0] ==  message[-1] or len(message[0])==0):                                                                     
IndexError: **string index out of range**

Answer 1

You need to compare for an empty string before you access its elements. Your condition should be:

if(len(message)==0 or message[0] ==  message[-1]):

And it should be len(message) and not len(message[0]) because if your message is empty, there would not be any message[0] .

Answer 2

You first need to make sure that the message is not empty string. use this method, it returns 0 which evaluates false, and true when first and last chars are same.

def first_and_last(message):
  return len(message) and message[0] == message[-1]

Answer 3

try this :

def first_and_last(message):
  if(len(message)==0):
     return True
  elif(message[0] ==  message[-1] or len(message[0])==0):
     return True  
  return False
print(first_and_last("else"))
print(first_and_last("tree"))
print(first_and_last(""))

The error was you have to mention the case of checking empty string as well since you were passing the empty string in the function.