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Python Ternary Operator

The ternary operator is a one-line way to choose between two answers, like 'if it is raining take an umbrella, otherwise wear sunglasses'. It saves you writing a longer if-else.

In this page:

  1. Conditional Expressions
  2. Checking Even or Odd
  3. Nested Ternary Expressions
  4. Inline Ternary in Functions
  5. Ternary with Lists
Syntax
python 
result = value_if_true if condition else value_if_false

Conditional Expressions

Python's ternary operator is formally called a conditional expression, written as value_if_true if condition else value_if_false — it lets you collapse a short if/else into a single line wherever an expression, not a statement, is expected.

Example: Conditional Expressions

python 
age = 20
status = "adult" if age >= 18 else "minor"  # conditional expression on one line
print(status)

Checking Even or Odd

A classic use is checking even or odd inline: "even" if n % 2 == 0 else "odd" evaluates the condition once and immediately produces whichever string applies, without a multi-line if block.

Example: Checking Even or Odd

python 
n = 7
print("even" if n % 2 == 0 else "odd")

Nested Ternary Expressions

Nesting one conditional expression inside another lets you pick between three or more outcomes, but readability drops fast past one level of nesting — if you need more than two branches, a normal if/elif/else block is usually clearer.

Example: Nested Ternary Expressions

python 
score = 75
grade = "A" if score >= 90 else "B" if score >= 70 else "C"  # nested ternary, evaluated left to right
print(grade)

Inline Ternary in Functions

Because a conditional expression is just an expression, it slots neatly into a return statement — return "pass" if score >= 60 else "fail" — letting a function pick its return value in one line instead of a multi-line branch.

Example: Inline Ternary in Functions

python 
def result(score):
    return "pass" if score >= 60 else "fail"  # ternary directly in the return statement

print(result(72))

Ternary with Lists

The same pattern works for selecting between two containers, like items = cached_items if use_cache else fresh_items, letting you swap which list or default a variable points to based on a single condition.

Example: Ternary with Lists

python 
use_cache = False
cached_items = ["old"]
fresh_items = ["new"]
items = cached_items if use_cache else fresh_items  # picks which list to use
print(items)
Related Topics

Python Operator Precedence · Python Increment & Decrement · Python Assignment Operators · Python Identity Operators

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Common Mistakes
  1. Writing the condition first as in C, x > 0 ? "pos" : "neg", which is a SyntaxError; Python uses "pos" if x > 0 else "neg".
  2. Omitting the else part, as in "pos" if x > 0, which is a SyntaxError.
  3. Nesting several ternaries into one line, which is hard to read and to debug; use if/elif/else instead.
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