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pythonpandassortingindexingconcatenation

Concatenating two Pandas DataFrames while maintaining index order

I am trying to concatenate two DataFrames, with the resulting DataFrame preserving the index in order of the original two. For example:

df = pd.DataFrame({'Houses':[10,20,30,40,50], 'Cities':[3,4,7,6,1]}, index = [1,2,4,6,8])


df2 = pd.DataFrame({'Houses':[15,25,35,45,55], 'Cities':[1,8,11,14,4]}, index = [0,3,5,7,9])

Using pd.concat([df, df2]) simply appends df2 to the end of df1. I am trying to instead concatenate them to produce correct index order (0 through 9).

Solution

  • Use concat with parameter sort for avoid warning and then DataFrame.sort_index:

    df = pd.concat([df, df2], sort=False).sort_index()

print(df)
   Cities  Houses
0       1      15
1       3      10
2       4      20
3       8      25
4       7      30
5      11      35
6       6      40
7      14      45
8       1      50
9       4      55