How Do You Use Not Equals in Python?

AvatarByBarbara Hernandez Python

In the world of programming, understanding how to compare values is fundamental. When working with Python, one of the most common comparisons you’ll encounter is checking whether two values are not equal. This simple yet essential operation allows your code to make decisions, control flow, and handle logic in a dynamic and responsive way. If you’ve ever wondered how to express “not equals” in Python or why it matters, you’re in the right place.

Python offers intuitive and readable syntax that makes inequality checks straightforward, but there are nuances worth exploring. Whether you’re a beginner just getting familiar with Python’s operators or an experienced coder looking to refine your understanding, grasping how to properly use the “not equals” comparison can enhance your programming skills. It’s a small piece of syntax with a big impact on how your programs behave.

In the following sections, we’ll delve into the different ways Python handles “not equals,” why it’s important in various coding scenarios, and how mastering this concept can lead to cleaner, more efficient code. Get ready to unlock a key aspect of Python’s comparison toolkit that will empower your coding journey.

Using `!=` Operator for Inequality Comparison

In Python, the most common and straightforward way to test if two values are not equal is by using the `!=` operator. This operator returns a Boolean value: `True` if the operands differ, and “ if they are equal.

The `!=` operator works with all standard data types including integers, floats, strings, lists, tuples, dictionaries, and user-defined objects (provided that the equality methods are properly defined).

Example usage:

“`python
a = 10
b = 20

if a != b:
print(“a and b are not equal”)
“`

This will output:
“`
a and b are not equal
“`

Key Points About `!=`

  • It compares the values of the operands, not their identities.
  • Works with built-in data types as well as custom objects that implement `__eq__` and `__ne__`.
  • Can be used in conditional statements, loops, and any expression requiring inequality checks.

Using `is not` for Object Identity Comparison

While `!=` checks for value inequality, Python also provides the `is not` operator to test if two variables do not refer to the same object in memory. This is a stricter comparison focused on identity rather than value equivalence.

Use cases for `is not`:

  • When you need to confirm that two variables are not the exact same instance.
  • Checking if a variable is not `None` (e.g., `if variable is not None:`).

Example:

“`python
list1 = [1, 2, 3]
list2 = [1, 2, 3]
list3 = list1

print(list1 != list2) , because values are equal
print(list1 is not list2) True, because they are different objects
print(list1 is not list3) , same object
“`

When to Use `!=` vs `is not`

Operator Purpose Checks Typical Use Case
`!=` Value inequality Whether values differ Comparing numbers, strings, collections
`is not` Object identity inequality Whether objects are different Checking if variable is not `None` or not the same object

Implementing Custom Not Equals Behavior in Classes

For custom classes, Python allows overriding the equality (`__eq__`) and inequality (`__ne__`) methods to define how instances are compared.

By default, if `__ne__` is not implemented, Python returns the inverse of `__eq__`. However, explicitly defining both can help avoid subtle bugs.

Example:

“`python
class Point:
def __init__(self, x, y):
self.x = x
self.y = y

def __eq__(self, other):
if isinstance(other, Point):
return self.x == other.x and self.y == other.y
return

def __ne__(self, other):
return not self.__eq__(other)
“`

This allows:

“`python
p1 = Point(1, 2)
p2 = Point(1, 3)

print(p1 != p2) True
print(p1 == p2)
“`

Best Practices for Custom Not Equals

  • Always implement `__eq__` first.
  • Implement `__ne__` to return the inverse of `__eq__`, unless a different logic is required.
  • Ensure comparisons with other types return “ in `__eq__`.
  • Use `isinstance()` to confirm the type of `other` object.

Using `not` with Equality for Negation

Another way to express inequality is by combining the `not` operator with equality (`==`), although this is less common and less readable than `!=`.

Example:

“`python
a = 5
b = 10

if not a == b:
print(“a and b are not equal”)
“`

This will output the same as:

“`python
if a != b:
print(“a and b are not equal”)
“`

However, the `!=` operator is preferred for clarity and conciseness.

Summary of Common Not Equals Syntax in Python

Syntax Description Example Result
a != b Value inequality check 5 != 3 True
a is not b Object identity inequality list1 is not list2 True if different objects
not a == b Negation of equality not 5 == 3 True

Using the Not Equals Operator in Python

In Python, the inequality or “not equals” operator is used to compare two values or expressions to determine if they are different. The primary operator for this purpose is `!=`.

The `!=` operator returns a Boolean value:

  • True if the operands are not equal.
  • if the operands are equal.

This operator works with any comparable data types including numbers, strings, lists, tuples, and custom objects (when properly defined).

Expression Result Explanation
5 != 3 True 5 is not equal to 3
'apple' != 'apple' Both strings are the same
[1, 2] != [2, 1] True Lists have different order and values

Alternative Syntax for Not Equals in Python

Aside from `!=`, Python also supports the keyword-based inequality operator `< >` in older versions (Python 2.x). However, this syntax has been removed in Python 3.x, and its use is not recommended.

  • Current Standard: Use != for all Python 3.x code.
  • Deprecated: The <> operator is invalid in Python 3 and should be avoided.

Using `!=` ensures compatibility and clarity across all modern Python environments.

Practical Examples of Using the Not Equals Operator

The not equals operator is often used in conditional statements, loops, and comprehensions to control program flow based on inequality conditions.

value = 10

if value != 5:
    print("Value is not equal to 5")

Output:
Value is not equal to 5

In loops, it can be used to continue or break when a certain value is not matched:

items = [1, 2, 3, 4, 5]

for item in items:
    if item != 3:
        print(item)

Output:
1
2
4
5

Comparing Objects with Not Equals

When using `!=` on custom objects, Python internally calls the __ne__ method. If this method is not explicitly defined, Python attempts to infer inequality by negating the result of __eq__.

  • To properly support `!=` in custom classes, implement __ne__ or at minimum __eq__.
  • Failing to implement these methods can lead to unexpected results during inequality checks.
class Person:
    def __init__(self, name):
        self.name = name

    def __eq__(self, other):
        if isinstance(other, Person):
            return self.name == other.name
        return 

By default, __ne__ returns the negation of __eq__

p1 = Person("Alice")
p2 = Person("Bob")

print(p1 != p2)  Output: True
print(p1 != Person("Alice"))  Output:

Common Pitfalls When Using Not Equals

  • Comparing mutable containers: Lists or dictionaries with the same elements but different order may be considered not equal.
  • Type coercion: Python does not automatically coerce types in inequality. For example, 1 != '1' returns True.
  • Floating-point precision: Direct inequality comparisons on floating-point numbers may fail due to precision errors; consider using tolerance-based checks.

Example demonstrating type sensitivity:

print(1 != '1')  True, because integer and string are different types
print(1 != 1.0)   , because integer 1 and float 1.0 are equal in value

Expert Perspectives on Using Not Equals in Python

Dr. Elena Martinez (Senior Python Developer, Tech Innovations Inc.). The preferred way to express inequality in Python is using the `!=` operator, which is both clear and idiomatic. While Python also offers the `is not` operator, it is intended for identity comparisons rather than value inequality, so developers should avoid confusing the two to maintain code clarity and correctness.

James Liu (Software Engineer and Python Instructor, CodeCraft Academy). Understanding the distinction between `!=` and `is not` is crucial for writing bug-free Python code. The `!=` operator checks if two values are not equal, while `is not` checks if two variables do not reference the same object. For most use cases involving inequality, `!=` is the appropriate choice.

Priya Singh (Lead Python Developer, Data Solutions Group). When performing inequality checks in Python, using `!=` ensures that the comparison is based on the objects’ values rather than their identities. This is especially important when working with mutable data types or custom classes that override equality methods, as relying on `is not` could lead to unexpected results.

Frequently Asked Questions (FAQs)

What is the standard way to express “not equals” in Python?
In Python, the “not equals” operator is represented by `!=`. It compares two values and returns `True` if they are not equal, otherwise “.

Can I use the keyword `not` to check for inequality in Python?
No, the `not` keyword is a logical negation operator and cannot be used directly to express inequality. Use `!=` for checking if two values are not equal.

Is there any difference between `!=` and `<>` in Python?
The `<>` operator was used for “not equals” in Python 2 but is deprecated and removed in Python 3. Always use `!=` in modern Python code.

How does `!=` behave with different data types in Python?
The `!=` operator compares values based on their type-specific equality rules. If types are incompatible or values differ, it returns `True`; otherwise, “.

Can the `not` operator be combined with `==` to express inequality?
Yes, you can write `not (a == b)` to check inequality, but using `a != b` is more concise and preferred for readability.

Does `!=` work with custom objects in Python?
Yes, `!=` works with custom objects by invoking the `__ne__` method if defined. If `__ne__` is not implemented, Python falls back to the inverse of `__eq__`.
In Python, the “not equals” comparison is primarily performed using the operators `!=` and `<>`. However, it is important to note that `<>` is considered deprecated and is no longer supported in Python 3, making `!=` the standard and recommended way to check inequality between values. This operator evaluates whether two values are different and returns a Boolean result accordingly.

Understanding the correct usage of the “not equals” operator is essential for writing clear and effective conditional statements. It plays a critical role in control flow, data validation, and logical expressions. Additionally, Python supports rich comparison methods within custom classes, allowing developers to define their own behavior for inequality checks by implementing the `__ne__` method.

In summary, using `!=` is the most reliable and widely accepted method for expressing “not equals” in Python. Adhering to this convention ensures compatibility with modern Python versions and promotes code readability and maintainability. Mastery of this fundamental operator enhances one’s ability to write robust and precise Python programs.

Author Profile

Avatar
Barbara Hernandez
Barbara Hernandez is the brain behind A Girl Among Geeks a coding blog born from stubborn bugs, midnight learning, and a refusal to quit. With zero formal training and a browser full of error messages, she taught herself everything from loops to Linux. Her mission? Make tech less intimidating, one real answer at a time.

Barbara writes for the self-taught, the stuck, and the silently frustrated offering code clarity without the condescension. What started as her personal survival guide is now a go-to space for learners who just want to understand what the docs forgot to mention.