Class ConfigExpression

monai/bundle/config_item.py:295–412

Subclass of :py:class:`monai.bundle.ConfigItem`, the `ConfigItem` represents an executable expression (execute based on ``eval()``, or import the module to the `globals` if it's an import statement). See also: - https://docs.python.org/3/library/functions.html#eval. For e

class ConfigExpression(ConfigItem):
    """
    Subclass of :py:class:`monai.bundle.ConfigItem`, the `ConfigItem` represents an executable expression
    (execute based on ``eval()``, or import the module to the `globals` if it's an import statement).

    See also:

        - https://docs.python.org/3/library/functions.html#eval.

    For example:

    .. code-block:: python

        import monai
        from monai.bundle import ConfigExpression

        config = "$monai.__version__"
        expression = ConfigExpression(config, id="test", globals={"monai": monai})
        print(expression.evaluate())

    Args:
        config: content of a config item.
        id: name of current config item, defaults to empty string.
        globals: additional global context to evaluate the string.

    """

    prefix = EXPR_KEY
    run_eval = run_eval

    def __init__(self, config: Any, id: str = "", globals: dict | None = None) -> None:
        super().__init__(config=config, id=id)
        self.globals = globals if globals is not None else {}

    def _parse_import_string(self, import_string: str) -> Any | None:
        """parse single import statement such as "from monai.transforms import Resize"""
        node = first(ast.iter_child_nodes(ast.parse(import_string)))
        if not isinstance(node, (ast.Import, ast.ImportFrom)):
            return None
        if len(node.names) < 1:
            return None
        if len(node.names) > 1:
            warnings.warn(f"ignoring multiple import alias '{import_string}'.")
        name, asname = f"{node.names[0].name}", node.names[0].asname
        asname = name if asname is None else f"{asname}"
        if isinstance(node, ast.ImportFrom):
            self.globals[asname], _ = optional_import(f"{node.module}", name=f"{name}")
            return self.globals[asname]
        if isinstance(node, ast.Import):
            self.globals[asname], _ = optional_import(f"{name}")
            return self.globals[asname]
        return None

    def evaluate(self, globals: dict | None = None, locals: dict | None = None) -> str | Any | None:
        """
        Execute the current config content and return the result if it is expression, based on Python `eval()`.
        For more details: https://docs.python.org/3/library/functions.html#eval.