How to modify data with IF-Else conditions in Python


Python Tutorial 2.0


After writing second article of python "Data Exploration and Sub-setting", the topic for next article hovering in my mind was using If-else

I went with the flow of my mind and started writing about "how to apply if and else condition in python?"


Do read it and let me know your feedback!

Let's create a sample dataset for learning IF-Else based logical operations:

import pandas as p

Namelist = ['Tango','Tango','Tango','Jolly','Jolly','Jolly','John','John','John']

Subjectlist=['math','history','science','math','history','science','math','history','science']
Markslist=[51,62,86,60,68,85,56,94,52]

Exam_Dictionary={ 'Name' : Namelist ,

                                  'Subject' : Subjectlist ,
                                  'Marks' : Markslist }

Exam_Data=p.DataFrame(Exam_Dictionary, columns=['Name','Subject' ,'Marks'])


Exam_Data



Output :














Let now learn the basic method of logical IF operation


Example -

if len(Exam_Data)==0 :
    print('Dataset has zero observations')
else:
    print('Dataset has observations')

Output :









Before going further about conditional statements, let me tell you about the map function.

     map( ), it helps to easily apply operation on a collection. 


     Syntax : map( function, sequence)


     Simple example:

     def g(a) : return a*a                # we are defining a function

     print(map(g, [1,2,3,4]))           # applying the function on the list


     Output would be : [1,4,9,16]


In the below example, we are applying map function on variable of a dataframe.



Create a variable using if-else condition...


1. If-else

# Creating a function 

Pass_Fail_Function=lambda x: 'Pass' if  x>=70 else 'Fail'  


 # The lambda function is a way to create temporary function in python. It is generally used with map() and reduce())



# Applying above mentioned function on marks field

Exam_Data['Result']=Exam_Data['Marks'].map(Pass_Fail_Function)

Output :














   
2. If-else if-else for more than two conditions


# Defining  function

def Grade_function(val):
    if val<60 :
        out='III'
    elif val>=60 & val<80:
        out='II'
    else:
        out='I'

    return out


# Applying above mentioned function on marks field

Exam_Data['Grade']=Exam_Data['Marks'].map(Grade_function)


Output :
















Hope now you can easily use IF ELSE conditions in Python, a lot more is going to come, till then ...

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