How to use isin() In Python Pandas

Method 2: Using semi join

On the created dataframes we perform left join and subset using isin() function to check if the part on which the datasets are merged is in the subset of the merged dataset.

Syntax:

DataFrame.isin(values)

Parameters:

values: iterable, Series, DataFrame or dict

Returns:

DataFrame

Example:

In the below code, we used the indicator to find the rows which are ‘Left_only’ and subset the merged dataset, and assign it to df. finally, we retrieve the part which is only in our first data frame df1. the output is antijoin of the two data frames.

Python3

# importing packages 
import pandas as pd 
  
# anti-join 
# creating dataframes using pd.DataFrame() method. 
df1 = pd.DataFrame({ 
    "city": ["new york", "chicago", "orlando", 'mumbai'], 
    "temperature": [21, 14, 35, 30], 
    "humidity": [65, 68, 75, 75], 
}) 
df2 = pd.DataFrame({ 
    "city": ["chicago", "new york", "orlando"], 
    "humidity": [67, 60, 70] 
}) 
  
# carrying out anti join using merge method 
df3 = df1.merge(df2, on='city', how='left', indicator=True) 
  
df = df3.loc[df3['_merge'] == 'left_only', 'city'] 
  
d = df1[df1['city'].isin(df)] 
  
print(d) 

Output:

     city  temperature  humidity
3  mumbai           30        75

How to LEFT ANTI join under some matching condition in Pandas

LEFT ANTI Join is the opposite of semi-join. excluding the intersection, it returns the left table. It only returns the columns from the left table and not the right.