Computer Science · Class 11 · Expressions & Operators

ExpressionsBooleans⏱️ 9 min read

Relational Operators

Arithmetic operators give you a number. These six operators give you only True or False. They compare two operands with each other, so they are also called comparison operators.

1The six comparisons

less than

2 < 3

True

greater than

12 > 3

True

less than or equal to

12 <= 3

False

greater than or equal to

12 >= 12

True

equal to

12 == 12

True

not equal to

12 != 10

True

Read each one as a question. 2 < 3 asks "is 2 less than 3?" The answer is yes, so Python gives True. 12 < 3 asks "is 12 less than 3?" The answer is no, so Python gives False.

Python prompt — interactive mode

>>> print(2 < 3)

True

>>> print(12 < 3)

False

>>> print(12 <= 3)

False

>>> print(12 <= 12) # less than OR equal to — the 'equal to' half is enough

True

>>> print(12 == 12)

True

>>> print(12 != 12)

False

Key Takeaway

Every relational operator gives a boolean value — True or False. It never gives a number, and it never gives text.

2Move the numbers, watch the answers

Move the sliders for a and b below. All six comparisons are answered again for the new values. Now make the two numbers equal and see which answers change. That is the difference between <= and <, and between >= and >.

Move the two numbers — every answer is True or False

a = 12

b = 3

12 < 3less than

False

12 > 3greater than

True

12 <= 3less than or equal to

False

12 >= 3greater than or equal to

True

12 == 3equal to

False

12 != 3not equal to

True

Each of these six answers is a bool. It is never a number, and never text.

Note

Notice that <, == and > can never be True at the same time. Of any two numbers, one is either smaller than, equal to, or greater than the other. Only one of these three can be true.

3Comparing things that are not numbers

== and != work on text also. Here you can see why the number 42 and the string '42' are not the same thing:

Python prompt — interactive mode

>>> print('cat' == 'cat')

True

>>> print('cat' == 'Cat') # capital C — a different character

False

>>> print(42 == '42') # a number is never equal to text

False

Tip

Python is case sensitive. This means 'cat' and 'Cat' are two different strings, so comparing them gives False.

4Try it yourself

Python prompt — interactive mode

# Ask Python a question. The answer is always True or False.

>>>

try

5Recap

Key Takeaway

The six relational operators — <, >, <=, >=, == and != — compare two operands, and always give a boolean value.

Quick Check

What does print(12 <= 12) show?

Quick Check

Which operator checks whether two values are equal?

Quick Check

What type of value does 5 > 3 give?

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Logical Operators 🔗