ค้นหาจำนวนบทความที่จัดพิมพ์โดยสถาบัน "University of Pennsylvania"
Find the number of papers published by the institution "University of Pennsylvania".
inst = pd.DataFrame(columns=['instid', 'name']); authorship = pd.DataFrame(columns=['paperid', 'instid']); papers = pd.DataFrame(columns=['title', 'paperid'])
papers.loc[papers['paperid'].isin(authorship.loc[inst[inst['name'] == 'University of Pennsylvania']['instid'], 'paperid']), 'title'].nunique()