如何在结构模式匹配的默认情况下访问匹配值？

Question

用Python3.10的match语句，是否可以使用默认情况下met的值？

或者这个是否需要在match之前赋值一个变量才能在默认情况下使用？

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

您可以使用 as pattern:

match expensive_calculation(argument):
  case 'APPLE':
    value = 'FOO'
  case 'ORANGE':
    value = 'BAR'
  case _ as argument: #here, using `as` to save the wildcard default to `argument`
    raise Exception(f"Wrong kind of fruit found: {str(argument)}")

如何在结构模式匹配的默认情况下访问匹配值？

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

python

pattern-matching

python-3.10