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): passp = 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# initializing objectgfg = Gfg()print("Before using setattr:\n" f"\tname: {gfg.name}\n" f"\tdescr: {gfg.descr}")# setting value using setattrsetattr(gfg, "name", "GeeksForGeeks")setattr(gfg, "descr", "CS Portal")print("After using setattr:\n" f"\tname: {gfg.name}\n" f"\tdescr: {gfg.descr}")# creating new attribute using setattrsetattr(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])# Driver Codeif __name__ == "__main__": # Creating the dictionary my_dict = {"Name": "Geeks", "Rank": "1223", "Subject": "Python"} result = Dict2Class(my_dict) # printing the result 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 # for read-only attribute n = property(name, None)p = Person()setattr(p, 'n', 'rajav') |
Output :
---> 16 setattr(p, 'n', 'rajav') AttributeError: can't set attribute
