Is Operator in Python

Last Updated on April 27, 2023 by Prepbytes

The is operator in Python is one of the most useful operators. Every operator can be used according to its applications and use cases similarly we can use the is operator in python for testing an object’s identity. While moving further with our article we will discuss all about the is operator in Python in detail, its syntax usage and examples, followed by its applications.

Is Operator

The is operator in Python is a comparison operator used to check if two objects refer to the same memory location. This means that the is operator checks whether two variables or objects have the same identity, rather than just the same value. The is operator in Python returns True if two variables or objects have the same identity and False otherwise. It is a powerful and commonly used operator in Python, and it is different from the == operator.

Syntax of the is Operator in Python

The syntax of the is operator in Python is as follows:

variable1 is variable2

In this syntax, variable1 and variable2 are the variables or objects being compared. If variable1 and variable2 have the same identity, the is operator in Python returns True, and in case of inequality, it returns False.

The is operator returns True if variable1 and variable2 have the same identity and False otherwise.

Usage of the is Operator in Python

The is operator in Python is often used to compare two objects and determine whether they are the same object or not. This is particularly useful when working with mutable objects such as lists and dictionaries, where the contents of the object may change over time. By using the is operator, you can check whether two variables or objects are actually the same object in memory, rather than just having the same value.

The is operator in Python is not only useful for checking if two objects refer to the same memory location but it can also be used to test if a variable or object is None. None is a unique value in Python that indicates the absence of a value. Using the is an operator to check if a variable or object is None can be valuable in scenarios where you need to determine if a value has been assigned or not.

Examples of the is Operator in Python

Let’s now take a look at some examples of the is operator in Python to see how it works in practice.

Example 1 of is Operator in Python: Comparing Two Integers
In this example, we will compare two integers using the is operator in Python:

Code Implementation

x = 5
y = 5
print(x is y)

Output

True

Explanation of the above example
In this example, we create two integer variables x and y with the same value of 5. We then use the is operator to compare x and y. Since integers are immutable objects in Python, x, and y are both pointing to the same object in the memory, so the is operator in Python returns True.

Example 2 of is Operator in Python: Comparing Two Strings
We will see the code implementation of a comparison of two strings using the is operator in Python.

Code Implementation

x = "hello"
y = "hello"
print(x is y)

Output

True

Explanation of the above example
In this example, we create two string variables x and y with the same value of "hello". We then use the is operator to compare x and y. Since strings are also immutable objects in Python, x, and y are both referencing the same object in memory, so the is operator returns True.

Example 3 of is Operator in Python: Comparing Two Lists
In this example, we will compare two list variables using the is operator in Python.

Code Implementation

x = [1, 2, 3]
y = [1, 2, 3]
print(x is y)

Output

False

Explanation of the above example
In this example, we create two list variables x and y with the same values of [1, 2, 3]. We then use the is operator to compare x and y. Since lists are mutable objects in Python, x, and y are not referencing the same object in memory, even though they have the same values. Therefore, the is operator in Python returns False.

Example 4 of is Operator in Python: Comparing a Variable to None
In this example, we will compare a variable to None using the is operator in Python and will see its code implementation.

Code Implementation

x = None
print(x is None)

Output

True

Explanation of the above example
In this example, we create a variable x with the value of None. We then use the is operator in Python to compare x to None. Since None is a singleton object in Python, all variables with the value of None are referencing the same object in memory. Therefore, the is operator returns True.

Example 5 of is Operator in Python: Comparing a Function’s Return Value to None
In this example, we will compare a function’s return value to None using the is operator in Python, and below is the code and implementation of the same.

Code Implementation

def get_value():
   return None
x = get_value()
print(x is None)

Output

True

Explanation of the above example
In this example, we define a function get_value() that returns None. We then call this function and store the return value in a variable x. We use the is operator in Python to compare x to None. Since None is a singleton object in Python, all variables with the value of None are referencing the same object in memory. Therefore, the is operator returns True.

Example 6 of is Operator in Python: Checking If a String is a Palindrome
We can also check whether the String is palindrome or not with the help of is operator in Python. The following code shows how to use it.

Code Implementation

def is_palindrome(s):
   for i in range(len(s)):
       if s[i] is not s[-i-1]:
           return False
   return True
print(is_palindrome("racecar"))
print(is_palindrome("python"))

Output

True
False

Explanation of the above example
In this example, we use the is operator in Python to compare the characters at opposite ends of the string s. If the characters are the same object in memory, we continue checking the next pair of characters. If any pair of characters is not the same object in memory, we return False. If all pairs of characters are the same object in memory, we return True.

Difference between == and is Operator in Python

The == and is operator in Python both are used for comparisons, but they are fundamentally different.

• The is operator is used to compare two objects and determine if they refer to the same memory location. On the other hand, the == operator is used to compare the values of two objects and determine if they are equal.
• The is Operator in Python checks if two variables or objects are the same instance in memory. In other words, it checks if the objects being compared are identical and not just equivalent. Whereas, the == operator checks if the objects being compared are equivalent and not necessarily identical.

Applications of is Operator in Python

Below are some of the applications of is operator in Python.

• Checking if two variables refer to the same object:
  When working with mutable objects in Python, it is important to know whether two variables refer to the same object or not. The is operator can be used to check if two variables refer to the same object in memory.

• Checking if a variable is None:
  In Python, None is a special object that represents the absence of a value. The is operator can be used to check if a variable is None. This is because None is a singleton object in Python, which means that all variables with the value of None are referencing the same object in memory.

• Checking if an object is an instance of a class:
  The is operator in Python can be used to check if an object is an instance of a particular class. This can be useful in scenarios where we want to check if an object belongs to a particular class before performing any operations on it.

• Checking if a variable or object is True or False:
  Python has two Boolean values, True and False, which are used to check whether the statement evaluates to true or not. The is operator in Python can be used to determine whether a variable or object represents True or False.

• Checking if a variable or object is a specific string or value:
  The is operator in Python can be used to check if a variable or object is a specific string or value. This can be useful in scenarios where we want to check if a variable or object has a specific value before performing any operations on it.

Conclusion
The is operator in Python is an important operator that allows us to test object identity. It checks whether two variables or objects refer to the same underlying object in memory, rather than just having the same value. This is especially useful when working with mutable objects like dictionaries or lists, where the contents can change dynamically. The is operator in Python allows you to verify if two variables or objects are in fact the same object in memory, rather than just having equivalent values. The is operator in Python can also be used to test whether a variable or object is None. Moreover, it is different from the == operator which only compares the values in the object.

Frequently Asked Questions

Here are some of the frequently asked questions about is operator in Python.

Ques 1. When should we use the is operator instead of the == operator?
Ans. We should use the is operator in Python when we want to test whether two objects are the same object in memory, and the == operator when we want to test whether two objects have the same value.

Ques 2. How does the is operator in Python work with mutable objects?
Ans. The is operator works the same way with mutable objects as it does with immutable objects. It tests whether two objects refer to the same object in memory.

Ques 3. Is it possible to use the is operator in Python to check if two strings have the same value?
Ans. No, the is operator in Python should not be used to test whether two strings have the same value. Instead, use the == operator.

Ques 4. Can the is operator in Python be used to compare two dictionaries?
Ans. Yes, the is operator in Python can be used to compare two dictionaries. It will return True if the two dictionaries are the same object in memory.