file_loaders

Description

This module provides the library with the capability to load files into Widget-s.

It provides a FileLoader base class, which is then subclassed by various filetype- specific parsers with their own parse method. The job of this method is to take the file contents as a string, and create a valid json tree out of it.

You can "run" a PTG YAML file by calling ptg -f <filename> in your terminal.

To use any YAML related features, the optional dependency PyYAML is required.

Implementation details

The main method of these classes is load, which takes a file-like object or a string, parses it and returns a WidgetNamespace instance. This can then be used to access all custom Widget definitions in the datafile.

This module highly depends on the serializer module. Each file loader uses its own Serializer instance, but optionally take a pre-instantiated Serializer at construction. As with that module, this one depends on it "knowing" all types of Widget-s you are loading. If you have custom Widget subclass you would like to use in file-based definitions, use the FileLoader.register method, passing in your custom class as the sole argument.

File structure

Regardless of filetype, all loaded files must follow a specific structure:

root
|- config
|   |_ custom global widget configuration
|
|- markup
|   |_ custom markup definitions
|
|- boxes
|   |_ custom box definitions
|
|_ widgets
    |_ custom widget definitions

The loading follows the order config -> markup -> boxes -> widgets. It is not necessary to provide all sections.

Example of usage

# -- data.yaml --

markup:
    label-style: '141 @61 bold'

boxes:
    WINDOW_BOX: [
        "left --- right",
        "left x right",
        "left --- right",
    ]

config:
    Window:
        styles:
            border: '[@79]{item}'
        box: SINGLE

    Label:
        styles:
            value: '[label-style]{item}'

widgets:
    MyWindow:
        type: Window
        box: WINDOW_BOX
        widgets:
            Label:
                value: '[210 bold]This is a title'

            Label: {}

            Splitter:
                widgets:
                    - Label:
                        parent_align: 0
                        value: 'This is an option'

                    - Button:
                        label: "Press me!"

            Label: {}
            Label:
                value: '[label-style]{item}'

# -- loader.py --

import pytermgui as ptg

with ptg.YamlLoader() as loader, open("data.yaml", "r") as datafile:
    namespace = loader.load(datafile)

with ptg.WindowManager() as manager:
    manager.add(namespace.MyWindow)
    manager.run()

# Alternatively, one could run `ptg -f "data.yaml"` to display all widgets defined.
# See `ptg -h`.

FileLoader

Bases: ABC

Base class for file loader objects.

These allow users to load pytermgui content from a specific filetype, with each filetype having their own loaders.

To use custom widgets with children of this class, you need to call FileLoader.register.

Source code in pytermgui/file_loaders.py

class FileLoader(ABC):
    """Base class for file loader objects.

    These allow users to load pytermgui content from a specific filetype,
    with each filetype having their own loaders.

    To use custom widgets with children of this class, you need to call `FileLoader.register`."""

    serializer: Serializer
    """Object-specific serializer instance. In order to use a specific, already created
    instance you need to pass it on `FileLoader` construction."""

    @abstractmethod
    def parse(self, data: str) -> dict[Any, Any]:
        """Parses string into a dictionary used by `pytermgui.serializer.Serializer`.

        This dictionary follows the structure defined above.
        """

    def __init__(self, serializer: Serializer | None = None) -> None:
        """Initialize FileLoader.

        Args:
            serializer: An optional `pytermgui.serializer.Serializer` instance. If not provided, one
                is instantiated for every FileLoader instance.
        """

        if serializer is None:
            serializer = Serializer()

        self.serializer = serializer

    def __enter__(self) -> FileLoader:
        """Starts context manager."""

        return self

    def __exit__(self, _: Any, exception: Exception, __: Any) -> bool:
        """Ends context manager."""

        if exception is not None:
            raise exception

    def register(self, cls: Type[widgets_m.Widget]) -> None:
        """Registers a widget to the serializer.

        Args:
            cls: The widget type to register.
        """

        self.serializer.register(cls)

    def bind(self, name: str, method: Callable[..., Any]) -> None:
        """Binds a name to a method.

        Args:
            name: The name of the method, as referenced in the loaded
                files.
            method: The callable to bind.
        """

        self.serializer.bind(name, method)

    def load_str(self, data: str) -> WidgetNamespace:
        """Creates a `WidgetNamespace` from string data.

        To parse the data, we use `FileLoader.parse`. To implement custom formats,
        subclass `FileLoader` with your own `parse` implementation.

        Args:
            data: The data to parse.

        Returns:
            A WidgetNamespace created from the provided data.
        """

        parsed = self.parse(data)

        # Get & load config data
        config_data = parsed.get("config")
        if config_data is not None:
            namespace = WidgetNamespace.from_config(config_data, loader=self)
        else:
            namespace = WidgetNamespace.from_config({}, loader=self)

        # Create aliases
        for key, value in (parsed.get("markup") or {}).items():
            tim.alias(key, value)

        # Create boxes
        for name, inner in (parsed.get("boxes") or {}).items():
            self.serializer.register_box(name, widgets_m.boxes.Box(inner))

        # Create widgets
        for name, inner in (parsed.get("widgets") or {}).items():
            widget_type = inner.get("type") or name

            box_name = inner.get("box")

            box = None
            if box_name is not None and box_name in namespace.boxes:
                box = namespace.boxes[box_name]
                del inner["box"]

            try:
                namespace.widgets[name] = self.serializer.from_dict(
                    inner, widget_type=widget_type
                )
            except AttributeError as error:
                raise ValueError(
                    f'Could not load "{name}" from data:\n{json.dumps(inner, indent=2)}'
                ) from error

            if box is not None:
                namespace.widgets[name].box = box

        return namespace

    def load(self, data: str | IO) -> WidgetNamespace:
        """Loads data from a string or a file.

        When an IO object is passed, its data is extracted as a string.
        This string can then be passed to `load_str`.

        Args:
            data: Either a string or file stream to load data from.

        Returns:
            A WidgetNamespace with the data loaded.
        """

        if not isinstance(data, str):
            data = data.read()

        assert isinstance(data, str)
        return self.load_str(data)

serializer: Serializer = serializer instance-attribute

Object-specific serializer instance. In order to use a specific, already created instance you need to pass it on FileLoader construction.

__enter__()

Starts context manager.

Source code in pytermgui/file_loaders.py

def __enter__(self) -> FileLoader:
    """Starts context manager."""

    return self

__exit__(_, exception, __)

Ends context manager.

Source code in pytermgui/file_loaders.py

def __exit__(self, _: Any, exception: Exception, __: Any) -> bool:
    """Ends context manager."""

    if exception is not None:
        raise exception

__init__(serializer=None)

Initialize FileLoader.

Parameters:

Name	Type	Description	Default
serializer	Serializer | None	An optional pytermgui.serializer.Serializer instance. If not provided, one is instantiated for every FileLoader instance.	None

Source code in pytermgui/file_loaders.py

def __init__(self, serializer: Serializer | None = None) -> None:
    """Initialize FileLoader.

    Args:
        serializer: An optional `pytermgui.serializer.Serializer` instance. If not provided, one
            is instantiated for every FileLoader instance.
    """

    if serializer is None:
        serializer = Serializer()

    self.serializer = serializer

bind(name, method)

Binds a name to a method.

Parameters:

Name	Type	Description	Default
name	str	The name of the method, as referenced in the loaded files.	required
method	Callable[..., Any]	The callable to bind.	required

Source code in pytermgui/file_loaders.py

def bind(self, name: str, method: Callable[..., Any]) -> None:
    """Binds a name to a method.

    Args:
        name: The name of the method, as referenced in the loaded
            files.
        method: The callable to bind.
    """

    self.serializer.bind(name, method)

load(data)

Loads data from a string or a file.

When an IO object is passed, its data is extracted as a string. This string can then be passed to load_str.

Parameters:

Name	Type	Description	Default
data	str | IO	Either a string or file stream to load data from.	required

Returns:

Type	Description
WidgetNamespace	A WidgetNamespace with the data loaded.

Source code in pytermgui/file_loaders.py

def load(self, data: str | IO) -> WidgetNamespace:
    """Loads data from a string or a file.

    When an IO object is passed, its data is extracted as a string.
    This string can then be passed to `load_str`.

    Args:
        data: Either a string or file stream to load data from.

    Returns:
        A WidgetNamespace with the data loaded.
    """

    if not isinstance(data, str):
        data = data.read()

    assert isinstance(data, str)
    return self.load_str(data)

load_str(data)

Creates a WidgetNamespace from string data.

To parse the data, we use FileLoader.parse. To implement custom formats, subclass FileLoader with your own parse implementation.

Parameters:

Name	Type	Description	Default
data	str	The data to parse.	required

Returns:

Type	Description
WidgetNamespace	A WidgetNamespace created from the provided data.

Source code in pytermgui/file_loaders.py

def load_str(self, data: str) -> WidgetNamespace:
    """Creates a `WidgetNamespace` from string data.

    To parse the data, we use `FileLoader.parse`. To implement custom formats,
    subclass `FileLoader` with your own `parse` implementation.

    Args:
        data: The data to parse.

    Returns:
        A WidgetNamespace created from the provided data.
    """

    parsed = self.parse(data)

    # Get & load config data
    config_data = parsed.get("config")
    if config_data is not None:
        namespace = WidgetNamespace.from_config(config_data, loader=self)
    else:
        namespace = WidgetNamespace.from_config({}, loader=self)

    # Create aliases
    for key, value in (parsed.get("markup") or {}).items():
        tim.alias(key, value)

    # Create boxes
    for name, inner in (parsed.get("boxes") or {}).items():
        self.serializer.register_box(name, widgets_m.boxes.Box(inner))

    # Create widgets
    for name, inner in (parsed.get("widgets") or {}).items():
        widget_type = inner.get("type") or name

        box_name = inner.get("box")

        box = None
        if box_name is not None and box_name in namespace.boxes:
            box = namespace.boxes[box_name]
            del inner["box"]

        try:
            namespace.widgets[name] = self.serializer.from_dict(
                inner, widget_type=widget_type
            )
        except AttributeError as error:
            raise ValueError(
                f'Could not load "{name}" from data:\n{json.dumps(inner, indent=2)}'
            ) from error

        if box is not None:
            namespace.widgets[name].box = box

    return namespace

parse(data) abstractmethod

Parses string into a dictionary used by pytermgui.serializer.Serializer.

This dictionary follows the structure defined above.

Source code in pytermgui/file_loaders.py

@abstractmethod
def parse(self, data: str) -> dict[Any, Any]:
    """Parses string into a dictionary used by `pytermgui.serializer.Serializer`.

    This dictionary follows the structure defined above.
    """

register(cls)

Registers a widget to the serializer.

Parameters:

Name	Type	Description	Default
cls	Type[widgets_m.Widget]	The widget type to register.	required

Source code in pytermgui/file_loaders.py

def register(self, cls: Type[widgets_m.Widget]) -> None:
    """Registers a widget to the serializer.

    Args:
        cls: The widget type to register.
    """

    self.serializer.register(cls)

JsonLoader

Bases: FileLoader

JSON specific loader subclass.

Source code in pytermgui/file_loaders.py

class JsonLoader(FileLoader):
    """JSON specific loader subclass."""

    def parse(self, data: str) -> dict[Any, Any]:
        """Parse JSON str.

        Args:
            data: JSON formatted string.

        Returns:
            Loadable dictionary.
        """

        return json.loads(data)

parse(data)

Parse JSON str.

Parameters:

Name	Type	Description	Default
data	str	JSON formatted string.	required

Returns:

Type	Description
dict[Any, Any]	Loadable dictionary.

Source code in pytermgui/file_loaders.py

def parse(self, data: str) -> dict[Any, Any]:
    """Parse JSON str.

    Args:
        data: JSON formatted string.

    Returns:
        Loadable dictionary.
    """

    return json.loads(data)

WidgetNamespace dataclass

Class to hold data on loaded namespace.

Source code in pytermgui/file_loaders.py

@dataclass
class WidgetNamespace:
    """Class to hold data on loaded namespace."""

    # No clue why `widgets` is seen as undefined here,
    # but not in the code below. It only seems to happen
    # in certain pylint configs as well.
    config: dict[
        Type[widgets_m.Widget], dict[str, Any]  # pylint: disable=undefined-variable
    ]
    widgets: dict[str, widgets_m.Widget]
    boxes: dict[str, widgets_m.boxes.Box] = field(default_factory=dict)

    @classmethod
    def from_config(cls, data: dict[Any, Any], loader: FileLoader) -> WidgetNamespace:
        """Creates a namespace from config data.

        Args:
            data: A dictionary of config data.
            loader: The `FileLoader` instance that should be used.

        Returns:
            A new WidgetNamespace with the given config.
        """

        namespace = WidgetNamespace({}, {})
        for name, config in data.items():
            obj = loader.serializer.known_widgets.get(name)
            if obj is None:
                raise KeyError(f"Unknown widget type {name}.")

            namespace.config[obj] = {
                "styles": obj.styles,
                "chars": obj.chars.copy(),
            }

            for category, inner in config.items():
                value: str | widgets_m.styles.MarkupFormatter

                if category not in namespace.config[obj]:
                    setattr(obj, category, inner)
                    continue

                for key, value in inner.items():
                    namespace.config[obj][category][key] = value

        namespace.apply_config()
        return namespace

    @staticmethod
    def _apply_section(
        widget: Type[widgets_m.Widget], title: str, section: dict[str, str]
    ) -> None:
        """Applies configuration section to the widget."""

        for key, value in section.items():
            if title == "styles":
                widget.set_style(key, value)
                continue

            widget.set_char(key, value)

    def apply_to(self, widget: widgets_m.Widget) -> None:
        """Applies namespace config to the widget.

        Args:
            widget: The widget in question.
        """

        def _apply_sections(
            data: dict[str, dict[str, str]], widget: widgets_m.Widget
        ) -> None:
            """Applies sections from data to the widget."""

            for title, section in data.items():
                self._apply_section(type(widget), title, section)

        data = self.config.get(type(widget))
        if data is None:
            return

        _apply_sections(data, widget)

        if hasattr(widget, "_widgets"):
            for inner in widget:
                inner_section = self.config.get(type(inner))

                if inner_section is None:
                    continue

                _apply_sections(inner_section, inner)

    def apply_config(self) -> None:
        """Apply self.config to current namespace."""

        for widget, settings in self.config.items():
            for title, section in settings.items():
                self._apply_section(widget, title, section)

    def __getattr__(self, attr: str) -> widgets_m.Widget:
        """Get widget by name from widget list."""

        if attr in self.widgets:
            return self.widgets[attr]

        return self.__dict__[attr]

__getattr__(attr)

Get widget by name from widget list.

Source code in pytermgui/file_loaders.py

def __getattr__(self, attr: str) -> widgets_m.Widget:
    """Get widget by name from widget list."""

    if attr in self.widgets:
        return self.widgets[attr]

    return self.__dict__[attr]

apply_config()

Apply self.config to current namespace.

Source code in pytermgui/file_loaders.py

def apply_config(self) -> None:
    """Apply self.config to current namespace."""

    for widget, settings in self.config.items():
        for title, section in settings.items():
            self._apply_section(widget, title, section)

apply_to(widget)

Applies namespace config to the widget.

Parameters:

Name	Type	Description	Default
widget	widgets_m.Widget	The widget in question.	required

Source code in pytermgui/file_loaders.py

def apply_to(self, widget: widgets_m.Widget) -> None:
    """Applies namespace config to the widget.

    Args:
        widget: The widget in question.
    """

    def _apply_sections(
        data: dict[str, dict[str, str]], widget: widgets_m.Widget
    ) -> None:
        """Applies sections from data to the widget."""

        for title, section in data.items():
            self._apply_section(type(widget), title, section)

    data = self.config.get(type(widget))
    if data is None:
        return

    _apply_sections(data, widget)

    if hasattr(widget, "_widgets"):
        for inner in widget:
            inner_section = self.config.get(type(inner))

            if inner_section is None:
                continue

            _apply_sections(inner_section, inner)

from_config(data, loader) classmethod

Creates a namespace from config data.

Parameters:

Name	Type	Description	Default
data	dict[Any, Any]	A dictionary of config data.	required
loader	FileLoader	The FileLoader instance that should be used.	required

Returns:

Type	Description
WidgetNamespace	A new WidgetNamespace with the given config.

Source code in pytermgui/file_loaders.py

@classmethod
def from_config(cls, data: dict[Any, Any], loader: FileLoader) -> WidgetNamespace:
    """Creates a namespace from config data.

    Args:
        data: A dictionary of config data.
        loader: The `FileLoader` instance that should be used.

    Returns:
        A new WidgetNamespace with the given config.
    """

    namespace = WidgetNamespace({}, {})
    for name, config in data.items():
        obj = loader.serializer.known_widgets.get(name)
        if obj is None:
            raise KeyError(f"Unknown widget type {name}.")

        namespace.config[obj] = {
            "styles": obj.styles,
            "chars": obj.chars.copy(),
        }

        for category, inner in config.items():
            value: str | widgets_m.styles.MarkupFormatter

            if category not in namespace.config[obj]:
                setattr(obj, category, inner)
                continue

            for key, value in inner.items():
                namespace.config[obj][category][key] = value

    namespace.apply_config()
    return namespace

YamlLoader

Bases: FileLoader

YAML specific loader subclass.

Source code in pytermgui/file_loaders.py

class YamlLoader(FileLoader):
    """YAML specific loader subclass."""

    def __init__(self, serializer: Serializer | None = None) -> None:
        """Initialize object, check for installation of PyYAML."""

        if YAML_ERROR is not None:
            raise RuntimeError(
                "YAML implementation module not found. Please install `PyYAML` to use `YamlLoader`."
            ) from YAML_ERROR

        super().__init__()

    def parse(self, data: str) -> dict[Any, Any]:
        """Parse YAML str.

        Args:
            data: YAML formatted string.

        Returns:
            Loadable dictionary.
        """

        assert yaml is not None
        return yaml.safe_load(data)

__init__(serializer=None)

Initialize object, check for installation of PyYAML.

Source code in pytermgui/file_loaders.py

def __init__(self, serializer: Serializer | None = None) -> None:
    """Initialize object, check for installation of PyYAML."""

    if YAML_ERROR is not None:
        raise RuntimeError(
            "YAML implementation module not found. Please install `PyYAML` to use `YamlLoader`."
        ) from YAML_ERROR

    super().__init__()

parse(data)

Parse YAML str.

Parameters:

Name	Type	Description	Default
data	str	YAML formatted string.	required

Returns:

Type	Description
dict[Any, Any]	Loadable dictionary.

Source code in pytermgui/file_loaders.py

def parse(self, data: str) -> dict[Any, Any]:
    """Parse YAML str.

    Args:
        data: YAML formatted string.

    Returns:
        Loadable dictionary.
    """

    assert yaml is not None
    return yaml.safe_load(data)