concatenate 2 columns into 1 pandas code example

Example 1: 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')

Example 2: concat 3 column in pandas

In[17]:df['combined']=df['bar'].astype(str)+'_'+df['foo']+'_'+df['new']

In[17]:df
Out[18]: 
   bar foo     new    combined
0    1   a   apple   1_a_apple
1    2   b  banana  2_b_banana
2    3   c    pear    3_c_pear