1.2.3 Arithmetic, relational and logical operators

Arithmetic Operators

Arithmetic operators perform mathematical calculations on numeric values. All return a numeric result.

Operator	Meaning	Example	Result
`+`	Addition	`7 + 3`	`10`
`-`	Subtraction	`7 - 3`	`4`
`*`	Multiplication	`7 * 3`	`21`
`/`	Division (real result)	`7 / 2`	`3.5`
`//`	Integer division (floor)	`7 // 2`	`3`
`%`	Modulus (remainder)	`7 % 2`	`1`
`**`	Exponentiation (power)	`2 ** 8`	`256`

Key pair: // and %

Integer division and modulus are complementary. For any division a / b:

a // b gives the whole number of times b goes into a
a % b gives what is left over

minutes = 137
hours = 137 // 60    # 2  (60 goes into 137 twice)
remaining = 137 % 60 # 17 (137 - 2*60 = 17)
print(hours, "hours and", remaining, "minutes")  # 2 hours and 17 minutes

Relational Operators

Relational operators compare two values and return a Boolean result: True or False. They are used in conditions for if statements and loops.

Operator	Meaning	Example	Result
`==`	Equal to	`5 == 5`	`True`
`!=`	Not equal to	`5 != 3`	`True`
`>`	Greater than	`7 > 3`	`True`
`>=`	Greater than or equal to	`5 >= 5`	`True`
`<`	Less than	`3 < 7`	`True`
`<=`	Less than or equal to	`3 <= 3`	`True`

Note: == tests equality; = assigns a value. Mixing them up is one of the most common errors in programming.

Logical Operators

Logical operators combine Boolean expressions. They are used when a condition depends on more than one test.

Operator	Meaning	Returns True when...
`and`	Both conditions must be true	Both sides are `True`
`or`	At least one condition must be true	Either side (or both) is `True`
`not`	Inverts the Boolean value	The operand is `False`

age = 17
has_ticket = True

# and: both conditions must be true
if age >= 18 and has_ticket:
    print("Admitted")
else:
    print("Not admitted")         # prints this: age fails

# or: either condition is enough
if age >= 18 or has_ticket:
    print("Can proceed")          # prints this: ticket is True

# not: inverts
if not has_ticket:
    print("Buy a ticket first")   # does not print

Key Takeaways

// gives the integer (floor) quotient; % gives the remainder — useful for time conversion, even/odd checks and cycling through values.
Relational operators always return True or False — use == to test equality, never =.
and requires both sides true; or requires at least one; not inverts.
Logical operators are used to combine relational expressions into compound conditions.