How to do an else (default) in match-case in python?

How to do an else (default) in match-case in python?

As of Python 3.10, match-case (PEP 634) introduced the case statement, which allows you to match patterns and execute code blocks based on those patterns. However, it does not have a direct else or default clause like the switch statement in some other programming languages.

To achieve a similar behavior to else or default in a match-case block, you can use case _ to match any other value that does not match the previous patterns. This can act as a default case, similar to the else block in other languages.

Here's an example of how to use case _ for default behavior in a match-case block:

from typing import Match def evaluate_expression(expr: str) -> int: match expr: case "add": return 10 + 20 case "subtract": return 50 - 30 case "multiply": return 5 * 6 case "divide": return 100 // 2 case _: return -1 # Default case result = evaluate_expression("divide") print(result) # Output: 50

In this example, we have a function evaluate_expression that takes a string expr and uses match-case to perform different calculations based on the value of expr. If none of the patterns match, the case _ block acts as a default case, and the function returns -1 as a default value.

By using case _, you can handle default behavior or any unmatched cases in a match-case block. It is a powerful feature that provides a more expressive and concise way to handle multiple conditions in Python code.

Examples

  1. "Python match-case else syntax example"

    • Description: This query seeks an example demonstrating the usage of the else keyword within a match-case statement in Python.
    x = 5 match x: case 1: print("x is 1") case 2: print("x is 2") case _: print("x is neither 1 nor 2")

  2. "Python match-case default branch example"

    • Description: This query aims to understand how to implement a default branch within a match-case statement in Python.
    def handle_input(input_value): match input_value: case 'a': print("Input is 'a'") case 'b': print("Input is 'b'") case _: print("Input is neither 'a' nor 'b'")

  3. "Python match-case statement with else block example"

    • Description: This query is looking for a demonstration of utilizing both case and else blocks within a match-case statement in Python.
    def check_value(value): match value: case 1: print("Value is 1") case 2: print("Value is 2") else: print("Value is neither 1 nor 2")

  4. "Python match-case default case usage"

    • Description: This query is interested in learning how to handle unspecified cases using the else or default case within a match-case statement.
    def process_input(input_data): match input_data: case "hello": print("Hello!") case "world": print("World!") else: print("Input not recognized")

  5. "Python match-case statement default behavior"

    • Description: This query aims to understand the default behavior of a match-case statement when no specific cases are matched.
    def process_option(option): match option: case 1: print("Option 1 selected") case 2: print("Option 2 selected") else: print("Invalid option")

  6. "Python match-case else branch usage"

    • Description: This query focuses on learning how to utilize the else branch within a match-case statement for handling unspecified cases.
    def process_value(value): match value: case "apple": print("It's an apple") case "banana": print("It's a banana") else: print("Unknown fruit")

  7. "Python match-case default scenario example"

    • Description: This query seeks an example illustrating a scenario where the default case in a match-case statement is used.
    def evaluate_grade(score): match score: case 90: print("Grade A") case 80: print("Grade B") else: print("Grade not specified")

  8. "Python match-case handling unspecified cases"

    • Description: This query looks for guidance on how to handle cases that are not explicitly defined within a match-case statement.
    def process_request(request): match request: case "GET": print("Handling GET request") case "POST": print("Handling POST request") else: print("Unsupported request method")

  9. "Python match-case statement with default behavior"

    • Description: This query aims to understand how a match-case statement behaves when no specific cases are matched, and the default branch is executed.
    def analyze_input(input_value): match input_value: case "yes": print("Affirmative response") case "no": print("Negative response") else: print("Response not understood")

  10. "Python match-case statement else clause usage"

    • Description: This query focuses on learning how to use the else clause effectively within a match-case statement to handle unspecified cases.
    def process_command(command): match command: case "start": print("Starting process") case "stop": print("Stopping process") else: print("Unknown command")

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