从DataFrame的子集：

>>> df[['Source','Destination','Attack Name']].head()

               Source                     Destination    Attack Name
0              10.x.x.116                 10.x.x.71      RDP Enforcement Violation
1              43.x.x.233                 152.x.x.148    Scanner Enforcement Violation
2  hn.kd.dhcp (61.x.x.192)                152.x.x.148    NaN
3             104.x.x.241                 152.x.x.116    Scanner Enforcement Violation
4              117.x.x.61                 152.x.x.52     NaN

我想统计每个目标来自前10个来源的攻击数量。
我试过这样的方法：

import pandas as pd

outReport='test.xlsx'
df = pd.read_csv("IPSLogs2.csv")

def statsPerAttacker():
        topSrc = df['Source'].value_counts()[:10]
        mastaSR = pd.Series()
        for ip in topSrc.to_dict():
                df_statsPerAttacker = df[df['Source']==ip][['Source', 'Destination', 'Attack Name']].value_counts().to_frame()
                mastaSR = pd.concat([mastaSR, df_statsPerAttacker], axis=1)

        with pd.ExcelWriter(outReport, engine='openpyxl') as writer:
                mastaSR.to_excel(writer, startcol=2, startrow=2, header=False)

if __name__ == '__main__':
    statsPerAttacker()

我确实得到了结果，但是最后一列在每次源IP迭代后向右移动一个位置（见屏幕截图）：
https://postimg.cc/8FBnq07g
我做错什么了？谢谢