import pandas as pd 
df = pd.read_csv('Nowcoder.csv',sep=',')
pd.set_option('display.width', 300) # 设置字符显示宽度
pd.set_option('display.max_rows', None) # 设置显示最大行
pd.set_option('display.max_columns', None)
print('%.2f'%df.Num_of_exercise.var(axis=0))
print('%.2f'%df.Number_of_submissions.std(axis=0))