Often you want to pick one of two values based on a condition. The long way is an if/else statement:

age: int = 20

if age >= 18:
    status: str = "adult"
else:
    status = "minor"

That’s five lines for a simple choice. Python offers a one-line shortcut called the ternary operator (also called a conditional expression):

age: int = 20
status: str = "adult" if age >= 18 else "minor"

That’s the whole pattern:

<value-if-true> if <condition> else <value-if-false>

Read it left to right: “give me 'adult' if age >= 18, otherwise 'minor'”.

When to use it

The ternary shines when you’re assigning or passing a value:

# pick a discount based on membership
member: bool = True
discount: float = 0.20 if member else 0.05

# print one of two messages
print("Pass" if score >= 50 else "Fail")

# in an f-string
print(f"You have {n} item{'s' if n != 1 else ''}")

When NOT to use it

Skip the ternary when:

  • The branches do something (calling functions, printing) rather than just produce a value
  • The condition is long or complex
  • Nesting starts to creep in

Nested ternaries quickly become unreadable:

# painful
grade: str = "A" if score >= 90 else "B" if score >= 80 else "C" if score >= 70 else "F"

# better
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "F"

A good rule: if you can’t read the ternary at a glance, use if/else.

A note on and/or tricks

You may see code like this in older Python:

status = age >= 18 and "adult" or "minor"

It works most of the time — but breaks subtly when the “true” value is falsy (0, "", []). The ternary doesn’t have this trap. Always prefer the ternary.

Summary of Section 3

You now know every operator Python has:

  • Arithmetic — + - * / // % **
  • Comparison — == != < > <= >=
  • Logical — and or not
  • Assignment — = += -= *= /= //= %= **=
  • Membership — in not in
  • Identity — is is not
  • Ternary — x if cond else y

These plus variables and types are enough to write small programs. From here we’ll start putting them together — first with control flow (decisions and loops), then with functions.

What’s next

Section 4: Control Flow — making your program take different paths and repeat actions.

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