ไม่มีค่าใช้จ่ายเอกสารกี่ฉบับ?
How many documents do not have any expense?
df1 = pd.DataFrame(columns=['document_id']); df2 = pd.DataFrame(columns=['document_id'])
df1.loc[~df1['document_id'].isin(df2['document_id']), 'document_id'].count()