merge two dataframes based on column
df_outer = pd.merge(df1, df2, on='id', how='outer') #here id is common column
df_outer
                                
                            merge two dataframes based on column
df_outer = pd.merge(df1, df2, on='id', how='outer') #here id is common column
df_outer
                                
                            pd merge on multiple columns
new_df = pd.merge(A_df, B_df,  how='left', left_on=['A_c1','c2'], right_on = ['B_c1','c2'])
                                
                            pandas merge multiple dataframes
import pandas as pd
from functools import reduce
# compile the list of dataframes you want to merge
data_frames = [df1, df2, df3]
df_merged = reduce(lambda  left,right: pd.merge(left,right,on=['key_col'],
                                            how='outer'), data_frames)
                                
                            combine dataframes with two matching columns
merged_df = DF2.merge(DF1, how = 'inner', on = ['date', 'hours'])
                                
                            pandas merge two columns from different dataframes
#suppose you have two dataframes df1 and df2, and 
#you need to merge them along the column id
df_merge_col = pd.merge(df1, df2, on='id')
                                
                            python add multiple columns to pandas dataframe
# Basic syntax:
df[['new_column_1_name', 'new_column_2_name']] = pd.DataFrame([[np.nan, 'word']], index=df.index)
# Where the columns you're adding have to be pandas dataframes
# Example usage:
# Define example dataframe:
import pandas as pd
import numpy as np
df = pd.DataFrame({
    'col_1': [0, 1, 2, 3],
    'col_2': [4, 5, 6, 7]
})
print(df)
   col_1  col_2
0      0      4
1      1      5
2      2      6
3      3      7
# Add several columns simultaneously:
df[['new_col_1', 'new_col_2', 'new_col_3']] = pd.DataFrame([[np.nan, 42, 'wow']], index=df.index)
print(df)
   col_1  col_2  new_col_1  new_col_2 new_col_3
0      0      4        NaN         42       wow
1      1      5        NaN         42       wow
2      2      6        NaN         42       wow
3      3      7        NaN         42       wow
# Note, this isn't much more efficient than simply doing three
#	separate assignments, e.g.:
df['new_col_1'] = np.nan
df['new_col_2'] = 42
df['new_col_3'] = 'wow'
                                
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