Operators

Operators are essential for performing various operations on variables and values. You may want to multiply two numbers or compare them to know which one is greater, and operators allow us to do it.

Arithmetic Operators

Arithmetic operators can be used with numerical variables such as int and float.

Description	Operator	Example
Addition	+	a + b
Subtraction	-	a - b
Multiplication	*	a * b
Division	/	a / b
Floor Division	//	a // b
Modulo	%	a % b
Exponentiation	**	a ** b

a = 9
b = 2
print('Subtraction:', a - b)
print('Division:', a / b)
print('Floor Division:', a // b)
print('Modulo:', a % b)
print('Power:', a ** b)

Subtraction: 7
Division: 4.5
Floor Division: 4
Modulo: 1
Power: 81

Comparison Operators

We can compare two variables (or a variable and a value) using comparison operators. They are applicable to numerical variables, strings and booleans.

Description	Operator	Example
Equal To	==	a == b
Not Equal To	!=	a != b
Greater Than	>	a > b
Less Than	<	a < b
Greater Than or Equal To	>=	a >= b
Less Than or Equal To	<=	a <= b

a = 5
b = 2
print("Equal To:", a == b)
print("Less Than:", a > b)
print("Not Equal To:", a != b)
print("Greater Than:", a < b)

Equal To: False
Less Than: True
Not Equal To: True
Greater Than: False

Logical Operators

Logical operators are used to combine conditional statements or negate them, and can only be applied to booleans.

Description	Operator	Example
Logical AND	and	(a == b) and (a > c)
Logical OR	or	(a > b) or (a < c)
Logical NOT	not	not (a > b)

a = 5
b = 2
c = 4
print("(a == b) and (a > c)", (a == b) and (a > c))
print("(a > b) or (a < c)", (a > b) or (a < c))
print("not (a > b):", not (a > b))

(a == b) and (a > c) False
(a > b) or (a < c) True
not (a > b): False

Exercise

Define two strings str1="Tuesday" and str2="Wednesday", and compare them (e.g. equal, greater and less than).

Answer

str1="Tuesday"
str2="Wednesday"

print(str1,"equal to",str2,":",str1==str2)
print(str1,"greater than",str2,":",str1>str2)
print(str1,"less than",str2,":",str1<str2)

Tuesday equal to Wednesday : False
Tuesday greater than Wednesday : False
Tuesday less than Wednesday : True

It is easy undersand that the operator == returns True if two strings are the same. But what do > and <?

Python doesn’t understand the meaning of works “Tuesday” and “Wednesday”, they are just two chains of characters. The operator > will return True if the string str1 comes after alphabetically than str2, and < will return True if the string str1 comes before alphabetically than str2.