Python 从数据帧中查找字符串中的子字符串索引

我有一个包含两列（和许多行）的数据帧，一列是完整序列，另一列包含子序列。

我想找到完整序列中子序列开始位置的索引，并将其添加为另一列：

我试过这个：

df["start"] = df.sequence.index(df.sub_sequence)

但这将返回：

TypeError:“RangeIndex”对象不可调用

我做错了什么

以下是df和我希望结束的df：

示例数据帧：

import pandas as pd 

data = {"sequence": ["abcde","fghij","klmno"], "sub_sequence": ["cde", "gh", "no"]}    
df = pd.DataFrame (data, columns = ['sequence','sub_sequence'])

  sequence sub_sequence
0    abcde          cde
1    fghij           gh
2    klmno           no

data2 = {"sequence": ["abcde","fghij","klmno"], "sub_sequence": ["cde", "gh", "no"], "start": [2,1,3]}
df2 = pd.DataFrame (data2, columns = ['sequence','sub_sequence','start'])

  sequence sub_sequence  start
0    abcde          cde      2
1    fghij           gh      1
2    klmno           no      3

---

预期结果：

import pandas as pd 

data = {"sequence": ["abcde","fghij","klmno"], "sub_sequence": ["cde", "gh", "no"]}    
df = pd.DataFrame (data, columns = ['sequence','sub_sequence'])

  sequence sub_sequence
0    abcde          cde
1    fghij           gh
2    klmno           no

data2 = {"sequence": ["abcde","fghij","klmno"], "sub_sequence": ["cde", "gh", "no"], "start": [2,1,3]}
df2 = pd.DataFrame (data2, columns = ['sequence','sub_sequence','start'])

  sequence sub_sequence  start
0    abcde          cde      2
1    fghij           gh      1
2    klmno           no      3

在列表中使用和：

df['start'] = [seq.index(sub) for seq, sub in zip(df['sequence'], df['sub_sequence'])]

或沿

轴=1使用：

结果:

  sequence sub_sequence  start
0    abcde          cde      2
1    fghij           gh      1
2    klmno           no      3