Python: One-Line Conditional Statements with Conditional Expressions (Ternary Operator)

python if statement syntax

I'd be glad to explain how to put a simple if-then-else statement on one line in Python:

Conditional Expressions (Ternary Operator):

Python offers a way to express an if-else statement in a compact form, all on one line, using conditional expressions. These are also known as the ternary operator, similar to some other programming languages.

Here's the syntax:

<condition> if <true_expression> else <false_expression>
  • <condition>: This is the expression that determines whether the true_expression or false_expression will be evaluated.
  • <true_expression>: This expression is evaluated if the <condition> is True.


result = "Even" if number % 2 == 0 else "Odd"
print(result)  # Output: Even (if number is even) or Odd (if number is odd)


  1. The condition number % 2 == 0 checks if the remainder of dividing number by 2 is 0 (even number).
  2. If the condition is True, "Even" is assigned to result.

Benefits and Considerations:

  • Readability: For very simple conditions and assignments, this approach can make code more concise and readable.
  • Overuse: While convenient, overuse of one-line if-else statements can make code less readable, especially for complex logic.
  • Nesting: You can nest conditional expressions for more intricate logic, but beware of excessive nesting that can reduce readability.
  • Multi-Line Logic: For more complex logic within the true_expression or false_expression, it's generally better to break it down into multiple lines for clarity.

In summary:

  • Use conditional expressions for simple if-else scenarios where readability is enhanced.
  • Prioritize code readability for complex logic by using multi-line if-else statements.
  • Consider the trade-off between compactness and clarity when choosing your approach.

Absolutely, here are some more example codes demonstrating the use of conditional expressions (ternary operator) in Python:

Checking Age for Voting Eligibility:

age = 20
can_vote = "Eligible" if age >= 18 else "Not Eligible"
print(can_vote)  # Output: Eligible (if age >= 18) or Not Eligible (if age < 18)

Assigning Default Values:

name = "Alice"
greeting = f"Hello, {name}!" if name else "Hello, World!"
print(greeting)  # Output: Hello, Alice! (if name has a value) or Hello, World! (if name is empty)

Setting File Permissions (assuming appropriate permissions):

is_admin = True
permission = "rw-r--r--" if is_admin else "r--r--r--"
print(permission)  # Output: rw-r--r-- (if is_admin) or r--r--r-- (if not is_admin)
# Note: This is for illustration purposes only. File permissions require caution.

List Comprehensions with Conditional Expressions:

numbers = [1, 2, 3, 4, 5]
doubles = [num * 2 if num % 2 == 0 else num for num in numbers]
print(doubles)  # Output: [2, 4, 6, 8, 10] (doubles even numbers)

Remember, while these one-line expressions can be handy, prioritize readability for complex logic using multi-line if-else statements.

While conditional expressions (ternary operator) offer a concise way to write simple if-else statements, Python provides some alternate methods for handling conditional logic, each with its own advantages:

Multi-Line if-else Statements:

These are the classic approach and remain the most readable option for complex logic:

if condition:
    # Code to execute if condition is True
    # Code to execute if condition is False

This allows you to break down complex logic into well-defined blocks, enhancing readability and maintainability.

Dictionary Lookups (for specific conditions):

If you have a set of conditions and corresponding actions, dictionaries can be a cleaner approach:

actions = {
    True: some_function1,
    False: some_function2

result = actions.get(condition, default_function)()  # Call appropriate function

This is useful when you have multiple conditions and want to avoid long chains of if-elif-else statements.

Lambda Functions (for simple logic):

For very simple logic within the conditional expression, lambda functions can be used:

result = (lambda: "Even")() if number % 2 == 0 else (lambda: "Odd")()
print(result)  # Output: Even (if number is even) or Odd (if number is odd)

This can be a concise approach for short calculations within the conditional expression. However, avoid excessive nesting for readability.

Match-case Statements (Python 3.10+):

Python 3.10 introduced the match-case statement, offering a powerful and readable alternative for complex conditional logic:

match condition:
    case True:
        # Code to execute if condition is True
    case False:
        # Code to execute if condition is False

This provides a clear and concise way to handle multiple conditions and patterns, especially helpful for data validation and state management.

Choosing the Right Method:

  • For simple logic: Conditional expressions or lambda functions can be suitable.
  • For complex logic or code readability: Multi-line if-else statements are generally preferred.
  • For specific conditions with corresponding actions: Dictionary lookups offer a cleaner approach.
  • For advanced pattern matching (Python 3.10+): The match-case statement shines.

Consider the complexity of your logic, readability for others, and your personal preference when selecting the most appropriate method.

python if-statement syntax

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