Boston Red Stockings แพ้กี่ครั้งในช่วงหลังฤดูกาลปี 2009?
How many times did Boston Red Stockings lose in 2009 postseason?
df_postseason = pd.DataFrame(columns=['team_id_loser', 'year']); df_team = pd.DataFrame(columns=['team_id_br', 'name'])
df_postseason[(df_postseason['year'] == '2009') & (df_postseason['team_id_loser'] == df_team[df_team['name'] == 'Boston Red Stockings']['team_id_br'].values[0])].shape[0]