Method from_yaml

test/cli/run_cli_test.py:730–807

(cls, filename, update=False, preferred=None, verbose=1)

    @classmethod
    def from_yaml(cls, filename, update=False, preferred=None, verbose=1):
        supported_libs = {None, "ruamel.yaml", "pyyaml"}
        if preferred not in supported_libs:
            raise NotImplementedError(f"{preferred} not in {supported_libs}")
        yaml_lib = None
        if preferred == "ruamel.yaml" or preferred is None:
            try:
                from ruamel.yaml import YAML

                yaml_lib = "ruamel.yaml"
            except ImportError:
                pass
        if yaml_lib is None:
            try:
                import yaml
                from yaml.resolver import Resolver

                # https://stackoverflow.com/a/36470466/
                # remove resolver entries for On/Off/Yes/No
                for ch in "OoYyNn":
                    if ch not in Resolver.yaml_implicit_resolvers:
                        continue
                    if len(Resolver.yaml_implicit_resolvers[ch]) == 1:
                        del Resolver.yaml_implicit_resolvers[ch]
                    else:
                        Resolver.yaml_implicit_resolvers[ch] = [
                            x
                            for x in Resolver.yaml_implicit_resolvers[ch]
                            if x[0] != "tag:yaml.org,2002:bool"
                        ]
                yaml_lib = "pyyaml"
            except ImportError:
                pass
        if preferred is None:
            preferred = "either ruamel.yaml or pyyaml"
        if yaml_lib is None:
            raise ImportError(
                f"this script needs {preferred} "
                "which can be installed using pip, conda, apt, yum, ..."
            )
        if update:
            if yaml_lib != "ruamel.yaml":
                raise ImportError("ruamel.yaml required to update YAML file")
        if yaml_lib == "pyyaml":
            with open(filename, encoding="utf-8") as fp:
                data = yaml.safe_load(fp)
        elif yaml_lib == "ruamel.yaml":
            typ = "rt" if update else "safe"
            yaml = YAML(typ=typ)
            yaml.width = 200
            yaml.preserve_quotes = True
            with open(filename, encoding="utf-8") as fp:
                data = yaml.load(fp)
        else:
            raise NotImplementedError(yaml_lib)

        if not isinstance(data, Mapping):
            raise ValueError(f"expected dict-like structure to {filename}")