a='sentence'
print(a[3])
fruits=['苹果','栗子','荔枝','梨子']
print(fruits)
words=['python','ai','date','abc','efghj','machine learning']
longest=words[0]
for x in words:
    if len(x)>len(longest):
    	longest=x
    	print(f"最长的字符串是'{longest}',长度为{len(longest)}")