Python setattr() method (original) (raw)

Last Updated : 19 Jun, 2023

Python setattr() method is used to assign the object attribute its value. The setattr() can also be used to initialize a new object attribute. Also, setattr() can be used to assign None to any object attribute.

Example :

Python3

class Person:

`` def __init__( self ):

`` pass

p = Person()

setattr (p, 'name' , 'kiran' )

print (f "name: {p.name}" )

Output :

name: kiran

Python setattr() Function Syntax

Syntax : setattr(obj, var, val)

Parameters :

• obj : Object whose which attribute is to be assigned.
• var : object attribute which has to be assigned.
• val : value with which variable is to be assigned.

Returns : None

Python setattr() Examples

How setattr() works in Python?

In the given example, we have defined a animal class with a class variable name and we are showing how can we set the value of the variable with setattr().

Python3

class Animal:

`` name = 'lucky'

p = Animal()

print ( 'Before modification:' , p.name)

setattr (p, 'name' , 'Woozoo' )

print ( 'After modification:' , p.name)

Output :

Before modification: lucky After modification: Woozoo

When the attribute is not found in setattr() in Python

In this example, we have defined a Gfg class and we have set the name and descr variables to None after that we have set the variable with setattr() and printed it. After that, we created a variable named a value that was not found in the class with setattr() and printing it in Python.

Python3

class Gfg:

`` name = None

`` descr = None

gfg = Gfg()

print ( "Before using setattr:\n"

`` f "\tname: {gfg.name}\n"

`` f "\tdescr: {gfg.descr}" )

setattr (gfg, "name" , "GeeksForGeeks" )

setattr (gfg, "descr" , "CS Portal" )

print ( "After using setattr:\n"

`` f "\tname: {gfg.name}\n"

`` f "\tdescr: {gfg.descr}" )

setattr (gfg, 'value' , 5 )

print (f "\nNew attribute created, gfg.value: {gfg.value}" )

Output :

Before using setattr: name: None descr: None After using setattr: name: GeeksForGeeks descr: CS Portal

New attribute created, gfg.value: 5

Python setattr() dict

Here we are creating attributes of the class ‘Dict2Class’ dynamically using setattr() function by passing a dictionary with some keys and values to the __init__() method of the class.

Python3

class Dict2Class( object ):

`` def __init__( self , my_dict):

`` for key in my_dict:

`` setattr ( self , key, my_dict[key])

if __name__ = = "__main__" :

`` my_dict = { "Name" : "Geeks" ,

`` "Rank" : "1223" ,

`` "Subject" : "Python" }

`` result = Dict2Class(my_dict)

`` print ( "After Converting Dictionary to Class : " )

`` print (result.Name, result.Rank, result.Subject)

`` print ( type (result))

Output :

After Converting Dictionary to Class : Geeks 1223 Python <class '__main__.Dict2Class'>

Python setattr() exception

Here we will create read-only attributes of the object using property() function in Python and if we try to set the attribute’s value using setattr() function then an exception will rise.

Python3

class Person:

`` def __init__( self ):

`` self ._name = None

`` def name( self ):

`` print ( 'name function called' )

`` return self ._name

`` n = property (name, None )

p = Person()

setattr (p, 'n' , 'rajav' )

Output :

---> 16 setattr(p, 'n', 'rajav') AttributeError: can't set attribute