from __future__ import annotations import abc from collections.abc import Callable, Hashable, Mapping, Sequence from enum import Enum from typing import ( TYPE_CHECKING, Any, Literal, Protocol, TypeVar, Union, runtime_checkable, ) if TYPE_CHECKING: # IPython import is relatively slow. Avoid if not necessary from IPython.display import DisplayObject # TODO import from typing (requires Python >=3.10) from typing_extensions import TypeAlias CollType = TypeVar("CollType", bound="DaskCollection") CollType_co = TypeVar("CollType_co", bound="DaskCollection", covariant=True) PostComputeCallable = Callable Key: TypeAlias = Union[str, bytes, int, float, tuple["Key", ...]] # FIXME: This type is a little misleading. Low level graphs are often # MutableMappings but HLGs are not Graph: TypeAlias = Mapping[Key, Any] # Potentially nested list of Dask keys NestedKeys: TypeAlias = list[Union[Key, "NestedKeys"]] class SchedulerGetCallable(Protocol): """Protocol defining the signature of a ``__dask_scheduler__`` callable.""" def __call__( self, dsk: Graph, keys: Sequence[Key] | Key, **kwargs: Any, ) -> Any: """Method called as the default scheduler for a collection. Parameters ---------- dsk : The task graph. keys : Key(s) corresponding to the desired data. **kwargs : Additional arguments. Returns ------- Any Result(s) associated with `keys` """ raise NotImplementedError("Inheriting class must implement this method.") class PostPersistCallable(Protocol[CollType_co]): """Protocol defining the signature of a ``__dask_postpersist__`` callable.""" def __call__( self, dsk: Graph, *args: Any, rename: Mapping[str, str] | None = None, ) -> CollType_co: """Method called to rebuild a persisted collection. Parameters ---------- dsk: Mapping A mapping which contains at least the output keys returned by __dask_keys__(). *args : Any Additional optional arguments If no extra arguments are necessary, it must be an empty tuple. rename : Mapping[str, str], optional If defined, it indicates that output keys may be changing too; e.g. if the previous output of :meth:`__dask_keys__` was ``[("a", 0), ("a", 1)]``, after calling ``rebuild(dsk, *extra_args, rename={"a": "b"})`` it must become ``[("b", 0), ("b", 1)]``. The ``rename`` mapping may not contain the collection name(s); in such case the associated keys do not change. It may contain replacements for unexpected names, which must be ignored. Returns ------- Collection An equivalent Dask collection with the same keys as computed through a different graph. """ raise NotImplementedError("Inheriting class must implement this method.") @runtime_checkable class DaskCollection(Protocol): """Protocol defining the interface of a Dask collection.""" @abc.abstractmethod def __dask_graph__(self) -> Graph: """The Dask task graph. The core Dask collections (Array, DataFrame, Bag, and Delayed) use a :py:class:`~dask.highlevelgraph.HighLevelGraph` to represent the collection task graph. It is also possible to represent the task graph as a low level graph using a Python dictionary. Returns ------- Mapping The Dask task graph. If the instance returns a :py:class:`dask.highlevelgraph.HighLevelGraph` then the :py:func:`__dask_layers__` method must be implemented, as defined by the :py:class:`~dask.typing.HLGDaskCollection` protocol. """ raise NotImplementedError("Inheriting class must implement this method.") @abc.abstractmethod def __dask_keys__(self) -> NestedKeys: """The output keys of the task graph. Note that there are additional constraints on keys for a Dask collection than those described in the :doc:`task graph specification documentation `. These additional constraints are described below. All keys must either be non-empty strings or tuples where the first element is a non-empty string, followed by zero or more arbitrary str, bytes, int, float, or tuples thereof. The non-empty string is commonly known as the *collection name*. All collections embedded in the dask package have exactly one name, but this is not a requirement. These are all valid outputs: - ``[]`` - ``["x", "y"]`` - ``[[("y", "a", 0), ("y", "a", 1)], [("y", "b", 0), ("y", "b", 1)]`` Returns ------- list A possibly nested list of keys that represent the outputs of the graph. After computation, the results will be returned in the same layout, with the keys replaced with their corresponding outputs. """ raise NotImplementedError("Inheriting class must implement this method.") @abc.abstractmethod def __dask_postcompute__(self) -> tuple[PostComputeCallable, tuple]: """Finalizer function and optional arguments to construct final result. Upon computation each key in the collection will have an in memory result, the postcompute function combines each key's result into a final in memory representation. For example, dask.array.Array concatenates the arrays at each chunk into a final in-memory array. Returns ------- PostComputeCallable Callable that receives the sequence of the results of each final key along with optional arguments. An example signature would be ``finalize(results: Sequence[Any], *args)``. tuple[Any, ...] Optional arguments passed to the function following the key results (the `*args` part of the ``PostComputeCallable``. If no additional arguments are to be passed then this must be an empty tuple. """ raise NotImplementedError("Inheriting class must implement this method.") @abc.abstractmethod def __dask_postpersist__(self) -> tuple[PostPersistCallable, tuple]: """Rebuilder function and optional arguments to construct a persisted collection. See also the documentation for :py:class:`dask.typing.PostPersistCallable`. Returns ------- PostPersistCallable Callable that rebuilds the collection. The signature should be ``rebuild(dsk: Mapping, *args: Any, rename: Mapping[str, str] | None)`` (as defined by the :py:class:`~dask.typing.PostPersistCallable` protocol). The callable should return an equivalent Dask collection with the same keys as `self`, but with results that are computed through a different graph. In the case of :py:func:`dask.persist`, the new graph will have just the output keys and the values already computed. tuple[Any, ...] Optional arguments passed to the rebuild callable. If no additional arguments are to be passed then this must be an empty tuple. """ raise NotImplementedError("Inheriting class must implement this method.") @abc.abstractmethod def __dask_tokenize__(self) -> Hashable: """Value that must fully represent the object.""" raise NotImplementedError("Inheriting class must implement this method.") __dask_optimize__: Any """Given a graph and keys, return a new optimized graph. This method can be either a ``staticmethod`` or a ``classmethod``, but not an ``instancemethod``. For example implementations see the definitions of ``__dask_optimize__`` in the core Dask collections: ``dask.array.Array``, ``dask.dataframe.DataFrame``, etc. Note that graphs and keys are merged before calling ``__dask_optimize__``; as such, the graph and keys passed to this method may represent more than one collection sharing the same optimize method. Parameters ---------- dsk : Graph The merged graphs from all collections sharing the same ``__dask_optimize__`` method. keys : Sequence[Key] A list of the outputs from ``__dask_keys__`` from all collections sharing the same ``__dask_optimize__`` method. **kwargs : Any Extra keyword arguments forwarded from the call to ``compute`` or ``persist``. Can be used or ignored as needed. Returns ------- MutableMapping The optimized Dask graph. """ __dask_scheduler__: staticmethod[SchedulerGetCallable] """The default scheduler ``get`` to use for this object. Usually attached to the class as a staticmethod, e.g.: >>> import dask.threaded >>> class MyCollection: ... # Use the threaded scheduler by default ... __dask_scheduler__ = staticmethod(dask.threaded.get) """ @abc.abstractmethod def compute(self, **kwargs: Any) -> Any: """Compute this dask collection. This turns a lazy Dask collection into its in-memory equivalent. For example a Dask array turns into a NumPy array and a Dask dataframe turns into a Pandas dataframe. The entire dataset must fit into memory before calling this operation. Parameters ---------- scheduler : string, optional Which scheduler to use like "threads", "synchronous" or "processes". If not provided, the default is to check the global settings first, and then fall back to the collection defaults. optimize_graph : bool, optional If True [default], the graph is optimized before computation. Otherwise the graph is run as is. This can be useful for debugging. kwargs : Extra keywords to forward to the scheduler function. Returns ------- The collection's computed result. See Also -------- dask.compute """ raise NotImplementedError("Inheriting class must implement this method.") @abc.abstractmethod def persist(self: CollType, **kwargs: Any) -> CollType: """Persist this dask collection into memory This turns a lazy Dask collection into a Dask collection with the same metadata, but now with the results fully computed or actively computing in the background. The action of function differs significantly depending on the active task scheduler. If the task scheduler supports asynchronous computing, such as is the case of the dask.distributed scheduler, then persist will return *immediately* and the return value's task graph will contain Dask Future objects. However if the task scheduler only supports blocking computation then the call to persist will *block* and the return value's task graph will contain concrete Python results. This function is particularly useful when using distributed systems, because the results will be kept in distributed memory, rather than returned to the local process as with compute. Parameters ---------- scheduler : string, optional Which scheduler to use like "threads", "synchronous" or "processes". If not provided, the default is to check the global settings first, and then fall back to the collection defaults. optimize_graph : bool, optional If True [default], the graph is optimized before computation. Otherwise the graph is run as is. This can be useful for debugging. **kwargs Extra keywords to forward to the scheduler function. Returns ------- New dask collections backed by in-memory data See Also -------- dask.persist """ raise NotImplementedError("Inheriting class must implement this method.") @abc.abstractmethod def visualize( self, filename: str = "mydask", format: str | None = None, optimize_graph: bool = False, **kwargs: Any, ) -> DisplayObject | None: """Render the computation of this object's task graph using graphviz. Requires ``graphviz`` to be installed. Parameters ---------- filename : str or None, optional The name of the file to write to disk. If the provided `filename` doesn't include an extension, '.png' will be used by default. If `filename` is None, no file will be written, and we communicate with dot using only pipes. format : {'png', 'pdf', 'dot', 'svg', 'jpeg', 'jpg'}, optional Format in which to write output file. Default is 'png'. optimize_graph : bool, optional If True, the graph is optimized before rendering. Otherwise, the graph is displayed as is. Default is False. color: {None, 'order'}, optional Options to color nodes. Provide ``cmap=`` keyword for additional colormap **kwargs Additional keyword arguments to forward to ``to_graphviz``. Examples -------- >>> x.visualize(filename='dask.pdf') # doctest: +SKIP >>> x.visualize(filename='dask.pdf', color='order') # doctest: +SKIP Returns ------- result : IPython.display.Image, IPython.display.SVG, or None See dask.dot.dot_graph for more information. See Also -------- dask.visualize dask.dot.dot_graph Notes ----- For more information on optimization see here: https://docs.dask.org/en/latest/optimize.html """ raise NotImplementedError("Inheriting class must implement this method.") @runtime_checkable class HLGDaskCollection(DaskCollection, Protocol): """Protocol defining a Dask collection that uses HighLevelGraphs. This protocol is nearly identical to :py:class:`~dask.typing.DaskCollection`, with the addition of the ``__dask_layers__`` method (required for collections backed by high level graphs). """ @abc.abstractmethod def __dask_layers__(self) -> Sequence[str]: """Names of the HighLevelGraph layers.""" raise NotImplementedError("Inheriting class must implement this method.") class _NoDefault(Enum): """typing-aware constant to detect when the user omits a parameter and you can't use None. Copied from pandas._libs.lib._NoDefault. Usage ----- from dask.typing import NoDefault, no_default def f(x: int | None | NoDefault = no_default) -> int: if x is no_default: ... """ no_default = "NO_DEFAULT" def __repr__(self) -> str: return "" no_default = _NoDefault.no_default NoDefault = Literal[_NoDefault.no_default]