How to concat panda dataframes so that they are sorted by year?-CodePudding

Say I have 2 df's

One simply just contains index and year such as:

(index)	Year
1	2000
2	2001
3	2002
4	2003

Then I have a dataframe that consist of index, year, and some other datapoint such as:

(index)	Year	data
1	2001	1.515
2	2003	2.631

How do I join them so that I only transfer over the relevant 'data' column and it properly aligns with the dates 2001 and 2003 in the 1st dataframe? Of-course I will be using this method to import many more columns. e.g:

(index)	Year	data	different data
1	2000		potato
2	2001	1.515
3	2002		pickle
4	2003	2.631

CodePudding user response：

Possible solution is the following:

import pandas as pd

data1 = {"Year": [2000, 2001, 2002, 2003]}
data2 = {"Year": [2001, 2003], "data": [1.515, 2.631]}

df1 = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

df = pd.merge(df1, df2, how="outer", on="Year")
df = df.fillna("")

df

Returns

CodePudding user response：

Do a left merge:

>>> df = df.merge(df2, how='left')
>>> df
   Year   data
0  2000    NaN
1  2001  1.515
2  2002    NaN
3  2003  2.631

# Optional:
>>> df = df.fillna('')
   Year   data
0  2000       
1  2001  1.515
2  2002       
3  2003  2.631