PythonOperatorsComparison Operators

Comparison (Relational) Operators

Comparison operators are used to compare two values. They are the foundation of decision-making in Python, as they evaluate to a boolean value: True or False. These are most commonly used in if statements and while loops to control the flow of a program.

The Core Comparison Operators

Equal ==

Checks if the values of two operands are equal.

Pyground

Check if the value of `a` is equal to 10.

Expected Output:

a == 10: True
a == b: True
a == c: False

Output:



Chained Comparisons


Python allows for a wonderfully readable feature called chained comparisons. You can write a sequence of comparisons that reads like natural language.


a < b < c is a shortcut for (a < b) and (b < c).


Pyground
Check if a person's age is between 18 and 30 (inclusive).
Expected Output:
Is the age 25 between 18 and 30? True
Is the age 35 between 18 and 30? False
Output:


Chained comparisons are efficient. In a < b < c, c is only evaluated if a < b is True. This is known as “short-circuiting.”


Comparing Different Types


    

  • Numbers: Integers and floats are compared based on their mathematical value. 10 == 10.0 is True.
    • 

  • Strings: Strings are compared lexicographically (alphabetical order). 'apple' < 'banana' is True.
    • 

  • Lists/Tuples: Sequences are compared element by element from left to right. The comparison stops as soon as a difference is found.
    • 

  • Unrelated Types: In Python 3, comparing completely unrelated types like a number and a string with ordering operators (<, >) will raise a TypeError.
    • 



Pyground
Compare two lists lexicographically.
Expected Output:
Is [1, 2, 5] < [1, 2, 10]? True
Output:


Customizing Comparisons for Your Objects


You can define how instances of your own classes are compared by implementing special “rich comparison” methods.


    

  • __eq__(self, other) for ==
    • 

  • __ne__(self, other) for !=
    • 

  • __lt__(self, other) for <
    • 

  • __gt__(self, other) for >
    • 

  • __le__(self, other) for <=
    • 

  • __ge__(self, other) for >=
    • 



Pyground
Create a Task class where tasks are compared based on their priority.
Expected Output:
task1 < task2: True
task1 == task3: True
task1 >= task2: False
Output:


The @functools.total_ordering decorator is a convenient helper. If you define __eq__ and at least one of __lt__, __gt__, __le__, or __ge__, it will automatically fill in the rest for you.
Arithmetic OperatorsAssignment & Compound Operators