Comparison and Logical Operators

Big idea

Comparison operators ask a question and answer True or False. Logical operators — and, or, not — combine those answers.

Comparisons

x = 7
print(x == 7)
print(x != 7)
print(x > 10)
print("apple" == "Apple")

output
True
False
False
False

String comparison is exact — a capital letter makes it a different string.

= assigns; == compares. Mixing them up is the classic mistake — x = 7 moves x, x == 7 asks about it.

Chained comparisons

Python lets you write a range check the way you would in maths:

age = 15
print(13 <= age <= 19)   # True — a teenager

and, or, not

• a and b — True only if both are True.
• a or b — True if at least one is True.
• not a — flips True and False.

sunny = True
warm = False
print(sunny and warm)
print(sunny or warm)
print(not warm)
print(sunny and not warm)

False
True
True
True

Short-circuiting

Python stops as soon as it knows the answer. In a and b, if a is False the whole thing is False, so b is never even looked at. That makes this safe:

count = 0
print(count != 0 and 100 / count > 5)   # False — the division never runs

Without short-circuiting, 100 / 0 would crash the program.

Watch it

A common slip

color = "green"
is_primary = color == "red" or "blue"
print(bool(is_primary))

output
False

color == "red" or "blue" means (color == "red") or ("blue"), and "blue" on its own is a non-empty string — always truthy. Write the comparison out in full both times: color == "red" or color == "blue".

Think of it like

A club door. "Over 18 and has a ticket" — you need both. "Member or on the guest list" — either one gets you in. not flips the bouncer's answer.

Key terms

• Comparison operator — ==, !=, <, >, <=, >=; gives a boolean.
• Logical operator — and, or, not; combines booleans.
• Short-circuit — Stopping early once the answer is known.