def exchange_val(my_string):
   return my_string[-1:] + my_string[1:-1] + my_string[:1]

my_string = “Hi there how are you”
print(“该字符串为：”)
print(my_string)
print(“修改后的字符串为：”)
print(exchange_val(my_string))

该字符串为：
Hi there how are you
修改后的字符串为：
ui there how are yoH