import pandas as pd

pd.set_option('display.width',300)
pd.set_option('display.max_rows',None)
pd.set_option('display.max_columns',None)

item1 = pd.read_csv('Nowcoder1.csv')
item2 = pd.read_csv('Nowcoder2.csv')

df = pd.merge(item1,item2,on='Nowcoder_ID',how='left')

sub_df = df[['Name','Num_of_exercise','Number_of_submissions']]

print(sub_df)