มีผู้สมัครกี่กลุ่มในเขตที่ Doc Hastings ดำรงตำแหน่ง
How many groups of candidates are there in there in the district where the incumbent is Doc Hastings?
df = pd.DataFrame(columns=['incumbent', '_candidates_2008'])
df[df['incumbent'] == 'Doc Hastings']['_candidates_2008'].count()