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Pandas percentage of total with groupby（16个答案）
4天前关闭。
用一个例子更容易解释，比如我有一个示例 Dataframe ，其中包含year、cc_rating和number_x。

df = pd.DataFrame({"year":{"0":2005,"1":2005,"2":2005,"3":2006,"4":2006,"5":2006,"6":2007,"7":2007,"8":2007},"cc_rating":{"0":"2","1":"2a","2":"2b","3":"2","4":"2a","5":"2b","6":"2","7":"2a","8":"2b"},"number_x":{"0":9368,"1":21643,"2":107577,"3":10069,"4":21486,"5":110326,"6":10834,"7":21566,"8":111082}})

df 

year    cc_rating   number_x
0   2005    2   9368
1   2005    2a  21643
2   2005    2b  107577
3   2006    2   10069
4   2006    2a  21486
5   2006    2b  110326
6   2007    2   10834
7   2007    2a  21566
8   2007    2b  111082

问题

我怎样才能得到每年number_x的百分比？含义：

直接除法不能工作，因为年份不能设置为原始df中的索引，因为它不是唯一的。
现在我正在做下面的事情，但是效率很低，我相信有更好的方法。

df= pd.merge(df, df.groupby('year').sum(), left_on='year',right_index=True)
df['%'] = round((df['number_x'] / df['number_y'])*100 , 2)
df = df.drop('number_y', axis=1)

谢谢！