我正在从文本文件阅读值，并尝试查找子字符串的索引，如下所示

df=pd.read_csv('break_sent.txt', index_col=False,encoding='utf-8',delimiter="\n",names=['sent'])
#print(df[:50])
#df.index = list(df.index)
df1= df[40:50]
print(len(df))
print(df1.index)
print("-------------------------------------------")
for i,row in df1.iterrows():
    string = row['sent']
    #print("string",string)
    d = df1[df1.sent.str.match(string)] # if the result includes more than 1 value then we know that substring and its matching parent string are present, then I will eliminate the substring from the dataframe
    if len(d.index > 2):
        index_val = df.index(string)
        df.drop(df.index(string),inpace=True)
        df.reset_index(level=None, drop=True, inplace=True)

当我运行这段代码时，我收到以下错误

Traceback (most recent call last):
  File "process.py", line 15, in <module>
    index_val = df.index(string)
    TypeError: 'RangeIndex' object is not callable

我尝试将范围索引转换为List

df.index = list(df.index)

但是Int64Index是不可调用的，怎么才能得到字符串的索引呢？