Class Expression

src/_pytest/mark/expression.py:311–353

A compiled match expression as used by -k and -m. The expression can be evaluated against different matchers.

@final
class Expression:
    """A compiled match expression as used by -k and -m.

    The expression can be evaluated against different matchers.
    """

    __slots__ = ("_code", "input")

    def __init__(self, input: str, code: types.CodeType) -> None:
        #: The original input line, as a string.
        self.input: Final = input
        self._code: Final = code

    @classmethod
    def compile(cls, input: str) -> Expression:
        """Compile a match expression.

        :param input: The input expression - one line.

        :raises SyntaxError: If the expression is malformed.
        """
        astexpr = expression(Scanner(input))
        code = compile(
            astexpr,
            filename="<pytest match expression>",
            mode="eval",
        )
        return Expression(input, code)

    def evaluate(self, matcher: ExpressionMatcher) -> bool:
        """Evaluate the match expression.

        :param matcher:
            A callback which determines whether an identifier matches or not.
            See the :class:`ExpressionMatcher` protocol for details and example.

        :returns: Whether the expression matches or not.

        :raises UsageError:
            If the matcher doesn&#x27;t support the expression. Cannot happen if the
            matcher supports all expressions.
        """
        return bool(eval(self._code, {"__builtins__": {}}, MatcherAdapter(matcher)))