我有两个数据框,都由一个名为month的日期列索引.第一个是df1,有八行.我关心的列是df [‘num_percent’],它看起来像这样：

2015-02-01    0.071549
2015-03-01    0.070368
2015-04-01    0.069291
2015-05-01    0.068394
2015-06-01    0.067452
2015-07-01    0.066302
2015-08-01    0.065543
2015-09-01    0.064591
Name: num_percent,dtype: float64

第二个数据帧有100,000行.我关心的专栏是df2 [‘total_quantity’],它的样本如下所示：

2014-11-01    324199
2014-12-01    378443
2015-01-01    367379
2015-02-01    336863
2015-03-01    380268
2015-04-01    386292
2015-05-01    373213
2015-06-01    403343
2015-07-01    414310
2015-08-01    403684
2015-09-01    420922
Name: total_quantity,dtype: int64

我想在df2中添加一个新列,它是df2 [‘total_quantity’]的值乘以df1中月份的相应值.

我怎样才能做到这一点？

如果我尝试：

df2['percent'] = df2['total_quantity'] * df1['num_percent']

我得到ValueError：无法从重复的轴重新索引.

更新：这里有一些数据和代码来复制问题：

data = {'month': ['2014-01-01','2014-02-01','2014-03-01'],'num_percent': [0.4,0.5,0.6]}
df1 = pd.DataFrame(data)
df1['month'] = pd.to_datetime(df1['month'])
df1 = df1.set_index('month')
data = {'month': ['2014-01-01','2014-03-01','2014-01-01'],'org': ['00K','00K','00L'],'total_quantity': [1000,1000,2000,1000]}
df2 = pd.DataFrame(data)
df2['month'] = pd.to_datetime(df2['month'])
df2 = df2.set_index('month')
# Both of these produce ValueError: cannot reindex... 
df2['percent'] = df1['num_percent'] * df2['total_quantity']
df2.loc[df2.index.isin(df1.index),'percent'] = df2['total_quantity'] * df1['num_percent']