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<h3>Variables in Python</h3>
<p>In this tutorial we will learn about Python Variables and their working in Python.</p><hr>
<h4>Understanding of Python variables:</h4>
<p>In Python, a variable is a reserved memory location to store values.
<br>A variable is like a container to store certain values. While the program is running ,
variables are accessed and they are changed sometimes, i.e a new value will be assigned to a that variable.</p><br>
<h4>How Variables in Python are different than other Languages?</h4>
<h4>How variables work in C?</h4>
<p>In C language whe we declare a vairable and assign value to it then <b>some space is created </b>
in memory by the given name and the given values is stored in it.
Suppose we write the statement <b>int a=42;</b>, then the following will be the memory diagram</p><br>
<img src="pythonphoto\Capture39.JPG" height="190"><br>
<p> Now if we declare another variable , with the same value ,then again the same process will take place.<br><br>Suppose we write,<b>int b=42;</b></p>
<img src="pythonphoto\Capture40.JPG" height="190"><br>
<p>Finally we assign a new value to an existing variables, then it's previous value gets <b>overwritten<br><br>Suppose we write,<b>a=43;</b></b></p><br>
<img src="pythonphoto\Capture41.JPG" height="190"><br>
<h4>How variables work in Python?</h4>
<p>In python when we assign value to a variable , then things are different than C.Suppose we write <b>a=42</b> in python , then python will create 2 things:<br>
<ul>
<li><b>An object in heap memory holding the value 42, and</b></li>
<li><b>A reference called a which will point to this object</b></li>
</ul>
</p><br>
<img src="pythonphoto\Capture42.JPG" height="290"><br>
<p>Now if we create another variable called b and assign it the same value, then Python will do the following :<br>
<ul>
<li><b>Create a new reference by the name b</b></li>
<li><b>Assign the address of the previously created object to the reference b because the value is same</b></li>
<li><b>So now both a and b are pointing to the same object</b></li>
</ul>
<img src="pythonphoto\Capture43.JPG"/><br>
<p>Finally if we assign a new value to the variable a,then like C,python will not overwrite the value. Rather it will do the following:<br><ul>
<li><b>Create a new object initialized with the new value</b></li>
<li><b>Assign the address of the newly created object to the reference a</b></li>
<li><b>However the reference b is still pointing to the same object</b></li>
</ul>
<img src="pythonphoto\Capture44.JPG"/><br>
<p>This behaviour of object in python is called "immutability". In other words when we cannot change the value of an object , we say it is immutable , otherwise we say it is mutable. Objects of biult-in type like(<b>int, float, str, bool, complex,tuple</b>) are immutabel. Objects of built -in type like(<b>list, set, dict</b>) are mutable</p><br>
<h4>String are also immutable</h4>
<p>String objects in python are also immutable.That is , once we have created a String object, then we cannot overwrite it's value.Although we can change the value of the String refernce by assigning it new String.</p><br>
<img src="pythonphoto\Capture45.JPG" ><br>
<h4>Summary</h4>
<ul>
<li>Variables are often referred as "envelop" or "buckets" where information can be maintained and referenced.
Like any other programming language(C, C++, Java, etc.) Python also uses a variable to store the information.</li>
<li>Variables can be declared by using any name. We can even use alphabets like a, aa, abc, etc.</li>
<li>In Python, Variables can be re-declared even after you have declared them.</li>
<li>You cannot concatenate string with number directly in Python,
you need to declare them as a separate variable, and after that, you can concatenate number with string</li>
</ul>
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