Joining two Pandas DataFrames using merge()

Last Updated : 17 Aug, 2020

Let us see how to join two Pandas DataFrames using the merge() function.

merge()

Syntax : DataFrame.merge(parameters)

Parameters :

right : DataFrame or named Series

how : {‘left’, ‘right’, ‘outer’, ‘inner’}, default ‘inner’

on : label or list

left_on : label or list, or array-like

right_on : label or list, or array-like

left_index : bool, default False

right_index : bool, default False

sort : bool, default False

suffixes : tuple of (str, str), default (‘_x’, ‘_y’)

copy : bool, default True

indicator : bool or str, default False

validate : str, optional

Returns : A DataFrame of the two merged objects.

Example 1 : Merging two Dataframe with same number of elements :

# importing the module 
import pandas as pd 
  
# creating the first DataFrame 
df1 = pd.DataFrame({"fruit" : ["apple", "banana", "avocado"], 
                    "market_price" : [21, 14, 35]}) 
display("The first DataFrame") 
display(df1) 
  
# creating the second DataFrame 
df2 = pd.DataFrame({"fruit" : ["banana", "apple", "avocado"], 
                    "wholesaler_price" : [65, 68, 75]}) 
display("The second DataFrame") 
display(df2) 
  
# joining the DataFrames 
display("The merged DataFrame") 
pd.merge(df1, df2, on = "fruit", how = "inner") 

Output :

Example 2 : Merging two Dataframe with different number of elements :

# importing the module 
import pandas as pd 
  
# creating the first DataFrame 
df1 = pd.DataFrame({"fruit" : ["apple", "banana",  
                               "avocado", "grape"], 
                    "market_price" : [21, 14, 35, 38]}) 
display("The first DataFrame") 
display(df1) 
  
# creating the second DataFrame 
df2 = pd.DataFrame({"fruit" : ["apple", "banana", "grape"], 
                    "wholesaler_price" : [65, 68, 71]}) 
display("The second DataFrame") 
display(df2) 
  
# joining the DataFrames 
# here both common DataFrame elements are in df1 and df2,  
# so it extracts apple, banana, grapes from df1 and df2.   
display("The merged DataFrame") 
pd.merge(df1, df2, on = "fruit", how = "inner") 