Why OOPs In Python?

Classes, Objects and Constructors

Instance and Class Variables

Class Methods In Python

Class Methods As Alternative Constructor

Static Methods In Python oops

Inheritance In Python oops

[Hindi] Magic/Dunder Methods In Python? | Object Oriented Programming Using Python Tutorial #8

[Hindi] Property Decorators, Setters & Deleters? | Object Oriented Programming Using Python #9

In the previous article, we discussed how to work with class methods. In this article, we are going to discuss the class method as an alternative constructor.&nbsp;
<pre class="language-python"><code>class Employee:
 def __init__(self,fname,lname,salary): 
 self.fname=fname
 self.lname=lname
 self.salary=salary

# Initializing the object
harry = Employee("harry","jackson",4400)
rohan = Employee("rohan","das",4400)


print(harry.fname,rohan.fname)</code></pre>
From the above code, it is clear that when we want to add a new object to the class Employee, we simply initialize the new object variable with the conditions such as fname,lname, and salary. Using the object name, we can call any function. Example : 
<pre class="language-python"><code>harry.increase()</code></pre>
In this above example, we have called the increase function using the object harry. This function, by default, takes the argument &ldquo;self&rdquo; which is our object. But in certain conditions, we do not require any object in the function. Thus, we started using the class method to avoid code inefficiency. Now the question is how we can use the class method as an alternative constructor.
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<h4>Starting with the solution:</h4>
Creating an object that holds a string. Initializing the object. Let the object name be lovish.
<pre class="language-python"><code>lovish = Employee.from_str("lovish-jackson-76000")</code></pre>
 
The employee is the class, and from_str is the method. Now, we will create a class method that will be treated as an alternative class method. The alternative class method will take a string as input and sets all the variables. Here, from_str is a new method in the Class.
<pre class="language-python"><code>@classmethod
 def from_str(cls,emp_string):
 fname,lname,salary= emp_string.split("-")
 return cls(fname,lname,salary)
</code></pre>
Let's understand the above code line by line :
<ol style="list-style-type: lower-alpha;">
<li style="font-weight: 400;" aria-level="1">Here, the method from_str takes the argument cls, which is our class Employee, and emp_string is the string provided.`</li>
<li>We are using a split function that returns a list and will be separated followed by the condition &ldquo;-&rdquo; and will be stored in the respective variables, i.e., fname, name, and salary. This is parsing the string.</li>
<li style="font-weight: 400;" aria-level="1">After the split, the variables will be populated in the respective variables,i.e., 
<pre class="language-python"><code>fname=lovish
lname=jackson
salary=76000k
</code></pre>
</li>
<li style="font-weight: 400;" aria-level="1">At last, we are calling the class constructor or returning cls (cls is our class Employee) with fname, name, and salary.</li>
<li style="font-weight: 400;" aria-level="1">from_str function will return an object that will be allocated in &ldquo;lovish&rdquo;</li>
</ol>
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<h4>Getting the output :</h4>
<pre class="language-python"><code>print(lovish.fname)
print(lovish.lname)
print(lovish.salary)</code></pre>
<h4>Output :</h4>
<pre class="language-python"><code>Lovish
Jackson
7600
</code></pre>
So, this article ends here. If you've enjoyed this article, then please share this article with your friends. In the next article, we are will discuss the static method. Till then, keep coding!
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