Title: Create a Column Based on a Conditional in pandas
Slug: pandas_create_column_using_conditional
Summary: Create a Column Based on a Conditional in pandas
Date: 2016-05-01 12:00
Category: Python
Tags: Data Wrangling
Authors: Chris Albon

Preliminaries



In [1]:

    
# Import required modules
import pandas as pd
import numpy as np

Make a dataframe



In [2]:

    
data = {'name': ['Jason', 'Molly', 'Tina', 'Jake', 'Amy'], 
        'age': [42, 52, 36, 24, 73], 
        'preTestScore': [4, 24, 31, 2, 3],
        'postTestScore': [25, 94, 57, 62, 70]}
df = pd.DataFrame(data, columns = ['name', 'age', 'preTestScore', 'postTestScore'])
df









    Out[2]:






  
    
      
      name
      age
      preTestScore
      postTestScore
    
  
  
    
      0
      Jason
      42
      4
      25
    
    
      1
      Molly
      52
      24
      94
    
    
      2
      Tina
      36
      31
      57
    
    
      3
      Jake
      24
      2
      62
    
    
      4
      Amy
      73
      3
      70

Add a new column for elderly



In [3]:

    
# Create a new column called df.elderly where the value is yes
# if df.age is greater than 50 and no if not
df['elderly'] = np.where(df['age']>=50, 'yes', 'no')



In [4]:

    
# View the dataframe
df









    Out[4]:






  
    
      
      name
      age
      preTestScore
      postTestScore
      elderly
    
  
  
    
      0
      Jason
      42
      4
      25
      no
    
    
      1
      Molly
      52
      24
      94
      yes
    
    
      2
      Tina
      36
      31
      57
      no
    
    
      3
      Jake
      24
      2
      62
      no
    
    
      4
      Amy
      73
      3
      70
      yes

	name	age	preTestScore	postTestScore	elderly
0	Jason	42	4	25	no
1	Molly	52	24	94	yes
2	Tina	36	31	57	no
3	Jake	24	2	62	no
4	Amy	73	3	70	yes