Python union，union 2个dataset数据

Union and union all in Pandas dataframe Python:

Union all of two data frames in pandas can be easily achieved by using concat() function. Lets see with an example. First lets create two data frames

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import pandas as pd import numpy as np   #Create a DataFrame df1 = {     'Subject':['semester1','semester2','semester3','semester4','semester1',                'semester2','semester3'],    'Score':[62,47,55,74,31,77,85]}   df2 = {     'Subject':['semester1','semester2','semester3','semester4'],    'Score':[90,47,85,74]}     df1 = pd.DataFrame(df1,columns=['Subject','Score']) df2 = pd.DataFrame(df2,columns=['Subject','Score'])   df1 df2

df1 will be

df2 will be

Union all of dataframes in pandas:

UNION ALL

concat() function in pandas creates the union of two dataframe.

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""" Union all in pandas""" df_union_all= pd.concat([df1, df2]) df_union_all

union all of two dataframes  df1 and df2 is created with duplicates. So the resultant dataframe will be

Union all of dataframes in pandas and reindex :

concat() function in pandas creates the union of two dataframe with ignore_index = True will reindex the dataframe

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""" Union all with reindex in pandas""" df_union_all= pd.concat([df1, df2],ignore_index=True) df_union_all

union all of two dataframes  df1 and df2 is created with duplicates and the index is changed. So the resultant dataframe will be

Union of dataframes in pandas:

                        UNION 

ref:http://www.datasciencemadesimple.com/union-and-union-all-in-pandas-dataframe-in-python-2/