使用 pandas - python 合并两个数据帧

Question

First of all thank you for your help.

I have two dataframes row indexed by date (DD-MM-YYYY HH:MM) as follows:

DF1
        date               temp       wind 
0   31-12-2002 23:00       12.3       80   
1   01-01-2004 00:00       15.2       NAN
2   01-01-2004 01:00       18.4       NAN 
                 ........ 

DF2
        date               temp       wind 
0   31-12-2002 23:00       14.5       86   
1   01-01-2003 00:00       28.7       98
2   01-01-2003 01:00       26.7       88
                ........
n   01-01-2004 00:00       34.5       23 
m   01-01-2004 01:00       35.7       NAN 

MergedDF
        date               temp       wind 
0   31-12-2002 23:00       12.3       80
1   01-01-2003 00:00       28.7       98
2   01-01-2003 01:00       26.7       88
                ........
n   01-01-2004 00:00       15.2       23 
m   01-01-2004 01:00       18.4       NAN 

In DF1 there's one whole year (2003) missing and also some NAN values in the rest of the years. Basically I want to merge both dataframes, adding the year missing and replacing NAN values if this information is in DF2.

Someone could help me? I don't know very well how to implement this on pyhton/pandas.

Answer 1

MergedDF = df1.append(df2).groupby('date', as_index=False).first()

as_index=False option of group_by is useful to keep the same table index in the aggregated output.

.first() will keep the first non-null value for each date.