How to access the matched value in the default case of structural pattern matching?

Question

With Python 3.10's match statement, is it possible to use the value met in the default case?

Or does this need to be assigned a variable before match so it can be used in the default case?

match expensive_calculation(argument):
    case 'APPLE':
        value = 'FOO'
    case 'ORANGE':
        value = 'BAR'
    case _:
        raise Exception(
           "Wrong kind of fruit found: " +
           str(expensive_calculation(argument))
           # ^ is it possible to get the default value in this case?
        )

Answer 1

You can use an as pattern:

match expensive_calculation(argument):
  case 'APPLE':
    value = 'FOO'
  case 'ORANGE':
    value = 'BAR'
  # Using `as` to assign the wildcard default to `argument_calc`.
  case _ as argument_calc:
    raise Exception(f"Wrong kind of fruit found: {argument_calc!r}")

Or, the variable name can be assigned directly:

match expensive_calculation(argument):
  case 'APPLE':
    value = 'FOO'
  case 'ORANGE':
    value = 'BAR'
  # Assign the default value to `argument_calc`.
  case argument_calc:
    raise Exception(f"Wrong kind of fruit found: {argument_calc!r}")