What is == comparing in python?

There’s a subtle difference between the Python identity operator (is) and the equality operator (==). Your code can run fine when you use the Python is operator to compare numbers, until it suddenly doesn’t. You might have heard somewhere that the Python is operator is faster than the == operator, or you may feel that it looks more Pythonic. However, it’s crucial to keep in mind that these operators don’t behave quite the same.

The == operator compares the value or equality of two objects, whereas the Python is operator checks whether two variables point to the same object in memory. In the vast majority of cases, this means you should use the equality operators == and !=, except when you’re comparing to None.

In this course, you’ll learn:

• What the difference is between object equality and identity
• When to use equality and identity operators to compare objects
• What these Python operators do under the hood
• Why using is and is not to compare values leads to unexpected behavior
• How to write a custom __eq__() class method to define equality operator behavior

These operators compare the values on either sides of them and decide the relation among them. They are also called Relational operators.

Assume variable a holds 10 and variable b holds 20, then −

Example

Assume variable a holds 10 and variable b holds 20, then −

#!/usr/bin/python

a = 21
b = 10
c = 0

if ( a == b ):
   print "Line 1 - a is equal to b"
else:
   print "Line 1 - a is not equal to b"

if ( a != b ):
   print "Line 2 - a is not equal to b"
else:
   print "Line 2 - a is equal to b"

if ( a <> b ):
   print "Line 3 - a is not equal to b"
else:
   print "Line 3 - a is equal to b"

if ( a < b ):
   print "Line 4 - a is less than b" 
else:
   print "Line 4 - a is not less than b"

if ( a > b ):
   print "Line 5 - a is greater than b"
else:
   print "Line 5 - a is not greater than b"

a = 5;
b = 20;
if ( a <= b ):
   print "Line 6 - a is either less than or equal to  b"
else:
   print "Line 6 - a is neither less than nor equal to  b"

if ( b >= a ):
   print "Line 7 - b is either greater than  or equal to b"
else:
   print "Line 7 - b is neither greater than  nor equal to b"

When you execute the above program it produces the following result −

Line 1 - a is not equal to b
Line 2 - a is not equal to b
Line 3 - a is not equal to b
Line 4 - a is not less than b
Line 5 - a is greater than b
Line 6 - a is either less than or equal to b
Line 7 - b is either greater than or equal to b

python_basic_operators.htm

Strings in Python are compared with == and != operators. These compare if two Python strings are equivalent or not equivalent, respectively. They return True or False.

Often, when you’re working with strings in Python, you may want to compare them to each other. For example, you may want to compare a user’s email address against the one you have stored in a database when you are asking them to reset their password.

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Python includes a number of comparison operators that can be used to compare strings. These operators allow you to check how strings compare to each other, and return a True or False value based on the outcome.

This tutorial will discuss the comparison operators available for comparing strings in Python. We’ll walk through an example of each of these operators to show how they work, and how you can use them in your code. If you’re looking to learn how to compare strings in Python, this article is for you.

Python String is and is Not Equal To

Strings are sequences of characters that can include numbers, letters, symbols, and whitespaces. Strings are an important data type because they allow coders to interact with text-based data in their programs.

When you’re working with a string, you may want to see whether a string is or is not equal to another string. That’s where the == and != string comparison operators come in.

The == equality operator returns True if two values match; otherwise, the operator returns False. The != operator returns True if two values do not match, and False if two values match.

It’s important to note that string comparisons are case sensitive. So, lowercase letters and uppercase letters will affect the result of the comparisons you perform in your Python program.

Let’s say that you are building a game that tests players on their knowledge of state capitals. In order to earn points, players must correctly answer a question. So, a player may be given the state California, and in order to gain points, they would need to enter that the capital is Sacramento into the program.

Here’s an example of this guessing game application that compares a user’s answer to the answer stored by the program:

random_state = "Delaware"

message = "What is the capital of ", random_state
user_answer = input(message)

state_capital = "Dover"

if user_answer == state_capital:
	print("You are correct!")
else:
	print("The capital of ", random_state, "is", state_capital)

Here’s what happens when we run our guessing game and correctly guess the state capital of Delaware is Dover:

What is the capital of Delaware
Dover
You are correct!

Our strings are equal, so our if statement evaluates to correct and prints out You are correct!. If we incorrectly guess the state capital is Denver, our code would return:

What is the capital of Delaware
Denver
The capital of Delaware of Dover

Let’s break down our code. On the first one, we declare our random state, which in this case is Delaware. Then, we use the user input() method to ask the user What is the capital of Delaware.

Our program then declares the state capital is Dover, and uses an if statement to compare whether the state capital the program has stored is equal to what the user has entered. 

When we entered Dover, the if statement evaluated to True, so our program printed the message You are correct! to the console. When we entered Denver, our statement evaluated to False, so our program executed the code in the else print statement.

Python is Operator

The most common method used to compare strings is to use the == and the != operators, which compares variables based on their values. However, if you want to compare whether two object instances are the same based on their object IDs, you may instead want to use is and is not.

The difference between == and is (and != and is not) is that the == comparison operator compares two variables based on their actual value, and the is keyword compares two variables based on their object ids.

Let’s use an example. Say that we have the scores of two users stored as a string, and we want to see whether or not they are the same. We could do so using the following code:

player_one_score = "100"
player_two_score = "100"

if player_one_score is player_two_score:
print("Player #1 and #2 have the same number of points.")
else:
	print("Player #1 and #2 do not have the same number of points.")

Our code returns:

Player #1 and #2 have the same number of points. 

In the above code, we could also have used the == operator. However, we used the is operator instead because it uses up less memory and we only needed to compare two objects.

The statement player_one_score is player_two_score evaluated to True in our program because both variables player_one_score and player_two_score have the same object IDs. We can check these IDs by using the id keyword:

print(id(player_one_score))
print(id(player_two_score))

Our code returns:

140239618130992
140239618130992

As you can see, our objects are the same, and so the is operator evaluated to True. Generally, you should use == when you’re comparing immutable data types like strings and numbers, and is when comparing objects.

Python Other Comparison Operators

In addition, you can compare strings in lexicographic order using Python. Lexicographic order refers to ordering letters based on the alphabetical order of their component letters. To do so, we can use the other comparison operators offered by Python. These are as follows:

• < – Less than
• > – Greater than
• <= – Less than or equal to
• >= – Greater than or equal to

Let’s say we were creating a program that takes in two student names and returns a message with whose name comes first in the alphabet.

We could use the following code to accomplish this task:

student_one = "Penny"
student_two = "Paul"

if student_one > student_two:
	print("Penny comes before Paul in the alphabet.")
elif student_one < student_two:
	print("Paul comes before Penny in the alphabet.")

Our code returns:

"Career Karma entered my life when I needed it most and quickly helped me match with a bootcamp. Two months after graduating, I found my dream job that aligned with my values and goals in life!"

Venus, Software Engineer at Rockbot

Paul comes before Penny in the alphabet.

Let’s break down our code. On the first two lines, we declare two variables that store our student names. In this case, these names are Penny and Paul.

Then, we create an if statement that uses the greater than operator to determine whether Penny’s name comes before Paul’s name in lexicographic order. If this evaluates to True, a message is printed to the console telling us that Penny comes before Paul in the alphabet.

We also create an elif statement that uses the less than operator to determine whether Penny’s name comes before Paul’s name in the alphabet. If this evaluates to True, a message is printed to the console telling the user that Paul comes before Penny in the alphabet.

In this case, Paul’s name comes before Penny’s in the alphabet, so the code in our elif block evaluates to true, and the message Paul comes before Penny in the alphabet. is printed to the console.

Conclusion

Comparing two strings is an important feature of Python. For instance, you may be creating a login form that needs to compare the password a user has entered with the password they have set for their account.

Python comparison operators can be used to compare strings in Python. These operators are: equal to (==), not equal to (!=), greater than (>), less than (<), less than or equal to (<=), and greater than or equal to (>=). This tutorial explored how these operators can be used to compare strings, and walked through a few examples of string comparison in Python.

You’re now ready to start comparing strings in Python like a pro!

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