It seems like you're trying to use the groupby function from pandas and then get the length of each group. However, len() is not a valid function to use with groupby. You might want to use size() or count() instead. Here's how you can do it:

df_1.groupby('文件名').size()

or

df_1.groupby('文件名').count()

These will return the number of rows in each group. If you want to count non-NA cells for each column or row, you should use count(). If you simply want to know the number of items in each group, you should use size().