python如何实现两列中行数据相同的次数统计

如图csv文件所示，我想得到某城市到某城市重复出现的次数。想要的效果如图：谢谢解答

import pandas as pd

data = pd.read_excel('c:/users/用户/desktop/数据.xlsx')

temp = [[name[0],name[1],len(group)] for name,group in data.groupby(['Origin','Destination'])]

data_re = pd.DataFrame(temp,columns=['Origin','Destination','count'])