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pythonpandasdataframesorting
viktor_dmitry
viktor_dmitry

Reputation: 103

How to group two appended dataframes by a column?

I have 2 dataframes with the same column names, for example:

col1 col2 col3
1    2    3

and

col1 col2 col3
4    5    6
1    7    8

I have appended them, so now the new dataframe is like below:

col1 col2 col3
1    2    3
4    5    6
1    7    8

The problem is that I need the rows that have the same value in the col1 to come one after the other, just like this:

col1 col2 col3
1    2    3
1    7    8
4    5    6

How can I sort the dataframe by col1 to create this effect(without modifying the dataframe type)?

Upvotes: 0

Views: 36

Answers (3)

Adrian Ang
Adrian Ang

Reputation: 580

You can sort a DataFrame by any column, for example:

df.sort_values(by=['col_1', 'col_2'], ascending=[True, False], inplace=True)

After that you may like to reset the row index, as they will be jumbled up:

df.reset_index(drop=True, inplace=True)

Upvotes: 0

el_oso
el_oso

Reputation: 1061

if you care about ensuring that dataframe 1 values are sorted before dataframe 2 values where they are tied, you can use the 'mergesort' algorithm. The default algorithm will arbritarily order any tied values.

df.sort_values(by='col1', axis=1, ascending=True, inplace=True, kind='mergesort')

Upvotes: 1

jezrael
jezrael

Reputation: 863166

Use DataFrame.sort_values:

df = pd.concat([df1, df2]).sort_values('col1', ignore_index=True)

Upvotes: 1

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