在Pandas身上没有得到确切的结果

Question

df=pandas.DataFrame(processed_data_format, columns=["file_name", "innings", "over","ball", "individual ball", "runs","batsman", "wicket_status","bowler_name","fielder_name"])      
a = {'runs':['sum'],'ball':['sum'],'file_name':['unique']}
t = df.groupby('batsman').agg(a)

运行此代码后，我得到的结果如下

['Younis Khan', array(['225245', '225247'], dtype=object), 113, 121]

但是我想得到这样的结果

['Younis Khan', 2 , 113, 121]

我需要获得文件名的计数，而不是数组（['225245'，'225247'，dtype=object）