pandas merge rows from two dataframes code example

Example 1: python dataframe left join

>>> left.merge(right, on='user_id', how='left')

Example 2: dataframe concatenate

# Pandas for Python

df['col1 & col2'] = df['col1']+df['col2']

#Output
#col1	col2	col1 & col2
#A1		A2		A1A2
#B1		B2		B1B2