python解决以下问题：输入一个英语单词have和一句话I had an apple and a banana确定该单词在句子中的词性注意：需要考虑单词变形要求时间复杂度尽可能低

可以使用Python中的nltk库来实现该功能。具体步骤如下：

1. 安装nltk库：在命令行中输入 pip install nltk 安装nltk库。

2. 导入nltk库中的word_tokenize和pos_tag函数：

   from nltk.tokenize import word_tokenize
   from nltk import pos_tag
   

3. 将输入的句子转化为单词列表，并使用pos_tag函数对每个单词进行词性标注：

   sentence = "I had an apple and a banana"
   word = "have"
   words = word_tokenize(sentence)
   word_pos = pos_tag(words)
   

4. 遍历单词列表，找到与输入单词相同或者相似的单词，并返回其词性：

   for w, pos in word_pos:
       if w == word or w.endswith(word) or w.startswith(word):
           print("The word '{}' is a '{}' in the sentence".format(word, pos))
           break
   else:
       print("The word '{}' is not found in the sentence".format(word))
   

完整代码如下：

from nltk.tokenize import word_tokenize
from nltk import pos_tag

sentence = "I had an apple and a banana"
word = "have"

words = word_tokenize(sentence)
word_pos = pos_tag(words)

for w, pos in word_pos:
    if w == word or w.endswith(word) or w.startswith(word):
        print("The word '{}' is a '{}' in the sentence".format(word, pos))
        break
else:
    print("The word '{}' is not found in the sentence".format(word))