มีกี่กรมธรรม์ที่ระบุไว้สำหรับลูกค้าที่ชื่อ "Dayana Robel"?
How many policies are listed for the customer named "Dayana Robel"?
df_customers = pd.DataFrame(columns=['customer_id', 'customer_name']); df_customers_policies = pd.DataFrame(columns=['customer_id'])
df_customers_policies[df_customers_policies['customer_id'].isin(df_customers[df_customers['customer_name'] == 'Dayana Robel']['customer_id'])].count().values[0]