[dask] Add type hints in Dask package (#3866)

* add type hints in dask module

* starting on asserts

* remove unused code

* add hints for dtypes

* replace accidentally-removed docstrings

* revert unrelated change

* Update python-package/lightgbm/dask.py

* empty commit

* fix hints on group

* capitalize array

* hide hints in signatures

* empty commit

* sphinx version

* Apply suggestions from code review

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* fix hint for MatrixLike

* Update python-package/lightgbm/dask.py

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* Apply suggestions from code review

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* update docstring

* empty commit

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

docs/conf.py

@@ -74,7 +74,7 @@ def run(self):
 RTD = bool(os.environ.get('READTHEDOCS', ''))
 
 # If your documentation needs a minimal Sphinx version, state it here.
-needs_sphinx = '1.3'  # Due to sphinx.ext.napoleon
+needs_sphinx = '2.1.0'  # Due to sphinx.ext.napoleon, autodoc_typehints
 if needs_sphinx > sphinx.__version__:
     message = 'This project needs at least Sphinx v%s' % needs_sphinx
     raise VersionRequirementError(message)
@@ -97,6 +97,9 @@ def run(self):
     "show-inheritance": True,
 }
 
+# hide type hints in API docs
+autodoc_typehints = "none"
+
 # Generate autosummary pages. Output should be set with: `:toctree: pythonapi/`
 autosummary_generate = ['Python-API.rst']
 

python-package/lightgbm/compat.py

@@ -113,7 +113,8 @@ def _check_sample_weight(sample_weight, X, dtype=None):
 try:
     from dask import delayed
     from dask.array import Array as dask_Array
-    from dask.dataframe import _Frame as dask_Frame
+    from dask.dataframe import DataFrame as dask_DataFrame
+    from dask.dataframe import Series as dask_Series
     from dask.distributed import Client, default_client, get_worker, wait
     DASK_INSTALLED = True
 except ImportError:
@@ -129,7 +130,12 @@ class dask_Array:
 
         pass
 
-    class dask_Frame:
-        """Dummy class for dask.dataframe._Frame."""
+    class dask_DataFrame:
+        """Dummy class for dask.dataframe.DataFrame."""
+
+        pass
+
+    class dask_Series:
+        """Dummy class for dask.dataframe.Series."""
 
         pass

python-package/lightgbm/dask.py

@@ -9,7 +9,7 @@
 import socket
 from collections import defaultdict
 from copy import deepcopy
-from typing import Dict, Iterable
+from typing import Any, Dict, Iterable, List, Optional, Type, Union
 from urllib.parse import urlparse
 
 import numpy as np
@@ -18,8 +18,13 @@
 from .basic import _choose_param_value, _ConfigAliases, _LIB, _log_warning, _safe_call, LightGBMError
 from .compat import (PANDAS_INSTALLED, pd_DataFrame, pd_Series, concat,
                      SKLEARN_INSTALLED,
-                     DASK_INSTALLED, dask_Frame, dask_Array, delayed, Client, default_client, get_worker, wait)
-from .sklearn import LGBMClassifier, LGBMRegressor, LGBMRanker
+                     DASK_INSTALLED, dask_DataFrame, dask_Array, dask_Series, delayed, Client, default_client, get_worker, wait)
+from .sklearn import LGBMClassifier, LGBMModel, LGBMRegressor, LGBMRanker
+
+_DaskCollection = Union[dask_Array, dask_DataFrame, dask_Series]
+_DaskMatrixLike = Union[dask_Array, dask_DataFrame]
+_DaskPart = Union[np.ndarray, pd_DataFrame, pd_Series, ss.spmatrix]
+_PredictionDtype = Union[Type[np.float32], Type[np.float64], Type[np.int32], Type[np.int64]]
 
 
 def _find_open_port(worker_ip: str, local_listen_port: int, ports_to_skip: Iterable[int]) -> int:
@@ -102,7 +107,7 @@ def _find_ports_for_workers(client: Client, worker_addresses: Iterable[str], loc
     return worker_ip_to_port
 
 
-def _concat(seq):
+def _concat(seq: List[_DaskPart]) -> _DaskPart:
     if isinstance(seq[0], np.ndarray):
         return np.concatenate(seq, axis=0)
     elif isinstance(seq[0], (pd_DataFrame, pd_Series)):
@@ -113,8 +118,15 @@ def _concat(seq):
         raise TypeError('Data must be one of: numpy arrays, pandas dataframes, sparse matrices (from scipy). Got %s.' % str(type(seq[0])))
 
 
-def _train_part(params, model_factory, list_of_parts, worker_address_to_port, return_model,
-                time_out=120, **kwargs):
+def _train_part(
+    params: Dict[str, Any],
+    model_factory: Type[LGBMModel],
+    list_of_parts: List[Dict[str, _DaskPart]],
+    worker_address_to_port: Dict[str, int],
+    return_model: bool,
+    time_out: int = 120,
+    **kwargs: Any
+) -> Optional[LGBMModel]:
     local_worker_address = get_worker().address
     machine_list = ','.join([
         '%s:%d' % (urlparse(worker_address).hostname, port)
@@ -158,7 +170,7 @@ def _train_part(params, model_factory, list_of_parts, worker_address_to_port, re
     return model if return_model else None
 
 
-def _split_to_parts(data, is_matrix):
+def _split_to_parts(data: _DaskCollection, is_matrix: bool) -> List[_DaskPart]:
     parts = data.to_delayed()
     if isinstance(parts, np.ndarray):
         if is_matrix:
@@ -169,24 +181,33 @@ def _split_to_parts(data, is_matrix):
     return parts
 
 
-def _train(client, data, label, params, model_factory, sample_weight=None, group=None, **kwargs):
+def _train(
+    client: Client,
+    data: _DaskMatrixLike,
+    label: _DaskCollection,
+    params: Dict[str, Any],
+    model_factory: Type[LGBMModel],
+    sample_weight: Optional[_DaskCollection] = None,
+    group: Optional[_DaskCollection] = None,
+    **kwargs: Any
+) -> LGBMModel:
     """Inner train routine.
 
     Parameters
     ----------
     client : dask.distributed.Client
         Dask client.
-    data : dask array of shape = [n_samples, n_features]
+    data : dask Array or dask DataFrame of shape = [n_samples, n_features]
         Input feature matrix.
-    label : dask array of shape = [n_samples]
+    label : dask Array, dask DataFrame or dask Series of shape = [n_samples]
         The target values (class labels in classification, real numbers in regression).
     params : dict
         Parameters passed to constructor of the local underlying model.
     model_factory : lightgbm.LGBMClassifier, lightgbm.LGBMRegressor, or lightgbm.LGBMRanker class
         Class of the local underlying model.
-    sample_weight : array-like of shape = [n_samples] or None, optional (default=None)
+    sample_weight : dask Array, dask DataFrame, Dask Series of shape = [n_samples] or None, optional (default=None)
         Weights of training data.
-    group : array-like or None, optional (default=None)
+    group : dask Array, dask DataFrame, Dask Series of shape = [n_samples] or None, optional (default=None)
         Group/query data.
         Only used in the learning-to-rank task.
         sum(group) = n_samples.
@@ -301,7 +322,15 @@ def _train(client, data, label, params, model_factory, sample_weight=None, group
     return results[0]
 
 
-def _predict_part(part, model, raw_score, pred_proba, pred_leaf, pred_contrib, **kwargs):
+def _predict_part(
+    part: _DaskPart,
+    model: LGBMModel,
+    raw_score: bool,
+    pred_proba: bool,
+    pred_leaf: bool,
+    pred_contrib: bool,
+    **kwargs: Any
+) -> _DaskPart:
     data = part.values if isinstance(part, pd_DataFrame) else part
 
     if data.shape[0] == 0:
@@ -332,15 +361,23 @@ def _predict_part(part, model, raw_score, pred_proba, pred_leaf, pred_contrib, *
     return result
 
 
-def _predict(model, data, raw_score=False, pred_proba=False, pred_leaf=False, pred_contrib=False,
-             dtype=np.float32, **kwargs):
+def _predict(
+    model: LGBMModel,
+    data: _DaskMatrixLike,
+    raw_score: bool = False,
+    pred_proba: bool = False,
+    pred_leaf: bool = False,
+    pred_contrib: bool = False,
+    dtype: _PredictionDtype = np.float32,
+    **kwargs: Any
+) -> dask_Array:
     """Inner predict routine.
 
     Parameters
     ----------
     model : lightgbm.LGBMClassifier, lightgbm.LGBMRegressor, or lightgbm.LGBMRanker class
         Fitted underlying model.
-    data : dask array of shape = [n_samples, n_features]
+    data : dask Array or dask DataFrame of shape = [n_samples, n_features]
         Input feature matrix.
     raw_score : bool, optional (default=False)
         Whether to predict raw scores.
@@ -357,16 +394,16 @@ def _predict(model, data, raw_score=False, pred_proba=False, pred_leaf=False, pr
 
     Returns
     -------
-    predicted_result : dask array of shape = [n_samples] or shape = [n_samples, n_classes]
+    predicted_result : dask Array of shape = [n_samples] or shape = [n_samples, n_classes]
         The predicted values.
-    X_leaves : dask array of shape = [n_samples, n_trees] or shape = [n_samples, n_trees * n_classes]
+    X_leaves : dask Array of shape = [n_samples, n_trees] or shape = [n_samples, n_trees * n_classes]
         If ``pred_leaf=True``, the predicted leaf of every tree for each sample.
-    X_SHAP_values : dask array of shape = [n_samples, n_features + 1] or shape = [n_samples, (n_features + 1) * n_classes] or list with n_classes length of such objects
+    X_SHAP_values : dask Array of shape = [n_samples, n_features + 1] or shape = [n_samples, (n_features + 1) * n_classes]
         If ``pred_contrib=True``, the feature contributions for each sample.
     """
     if not all((DASK_INSTALLED, PANDAS_INSTALLED, SKLEARN_INSTALLED)):
         raise LightGBMError('dask, pandas and scikit-learn are required for lightgbm.dask')
-    if isinstance(data, dask_Frame):
+    if isinstance(data, dask_DataFrame):
         return data.map_partitions(
             _predict_part,
             model=model,
@@ -392,11 +429,21 @@ def _predict(model, data, raw_score=False, pred_proba=False, pred_leaf=False, pr
             **kwargs
         )
     else:
-        raise TypeError('Data must be either Dask array or dataframe. Got %s.' % str(type(data)))
+        raise TypeError('Data must be either dask Array or dask DataFrame. Got %s.' % str(type(data)))
 
 
 class _DaskLGBMModel:
-    def _fit(self, model_factory, X, y, sample_weight=None, group=None, client=None, **kwargs):
+
+    def _fit(
+        self,
+        model_factory: Type[LGBMModel],
+        X: _DaskMatrixLike,
+        y: _DaskCollection,
+        sample_weight: Optional[_DaskCollection] = None,
+        group: Optional[_DaskCollection] = None,
+        client: Optional[Client] = None,
+        **kwargs: Any
+    ) -> "_DaskLGBMModel":
         if not all((DASK_INSTALLED, PANDAS_INSTALLED, SKLEARN_INSTALLED)):
             raise LightGBMError('dask, pandas and scikit-learn are required for lightgbm.dask')
         if client is None:
@@ -420,13 +467,13 @@ def _fit(self, model_factory, X, y, sample_weight=None, group=None, client=None,
 
         return self
 
-    def _to_local(self, model_factory):
+    def _to_local(self, model_factory: Type[LGBMModel]) -> LGBMModel:
         model = model_factory(**self.get_params())
         self._copy_extra_params(self, model)
         return model
 
     @staticmethod
-    def _copy_extra_params(source, dest):
+    def _copy_extra_params(source: Union["_DaskLGBMModel", LGBMModel], dest: Union["_DaskLGBMModel", LGBMModel]) -> None:
         params = source.get_params()
         attributes = source.__dict__
         extra_param_names = set(attributes.keys()).difference(params.keys())
@@ -437,7 +484,14 @@ def _copy_extra_params(source, dest):
 class DaskLGBMClassifier(LGBMClassifier, _DaskLGBMModel):
     """Distributed version of lightgbm.LGBMClassifier."""
 
-    def fit(self, X, y, sample_weight=None, client=None, **kwargs):
+    def fit(
+        self,
+        X: _DaskMatrixLike,
+        y: _DaskCollection,
+        sample_weight: Optional[_DaskCollection] = None,
+        client: Optional[Client] = None,
+        **kwargs: Any
+    ) -> "DaskLGBMClassifier":
         """Docstring is inherited from the lightgbm.LGBMClassifier.fit."""
         return self._fit(
             model_factory=LGBMClassifier,
@@ -455,7 +509,7 @@ def fit(self, X, y, sample_weight=None, client=None, **kwargs):
                    + ' ' * 12 + 'Dask client.\n'
                    + ' ' * 8 + _init_score + _after_init_score)
 
-    def predict(self, X, **kwargs):
+    def predict(self, X: _DaskMatrixLike, **kwargs: Any) -> dask_Array:
         """Docstring is inherited from the lightgbm.LGBMClassifier.predict."""
         return _predict(
             model=self.to_local(),
@@ -466,7 +520,7 @@ def predict(self, X, **kwargs):
 
     predict.__doc__ = LGBMClassifier.predict.__doc__
 
-    def predict_proba(self, X, **kwargs):
+    def predict_proba(self, X: _DaskMatrixLike, **kwargs: Any) -> dask_Array:
         """Docstring is inherited from the lightgbm.LGBMClassifier.predict_proba."""
         return _predict(
             model=self.to_local(),
@@ -477,7 +531,7 @@ def predict_proba(self, X, **kwargs):
 
     predict_proba.__doc__ = LGBMClassifier.predict_proba.__doc__
 
-    def to_local(self):
+    def to_local(self) -> LGBMClassifier:
         """Create regular version of lightgbm.LGBMClassifier from the distributed version.
 
         Returns
@@ -491,7 +545,14 @@ def to_local(self):
 class DaskLGBMRegressor(LGBMRegressor, _DaskLGBMModel):
     """Distributed version of lightgbm.LGBMRegressor."""
 
-    def fit(self, X, y, sample_weight=None, client=None, **kwargs):
+    def fit(
+        self,
+        X: _DaskMatrixLike,
+        y: _DaskCollection,
+        sample_weight: Optional[_DaskCollection] = None,
+        client: Optional[Client] = None,
+        **kwargs: Any
+    ) -> "DaskLGBMRegressor":
         """Docstring is inherited from the lightgbm.LGBMRegressor.fit."""
         return self._fit(
             model_factory=LGBMRegressor,
@@ -509,7 +570,7 @@ def fit(self, X, y, sample_weight=None, client=None, **kwargs):
                    + ' ' * 12 + 'Dask client.\n'
                    + ' ' * 8 + _init_score + _after_init_score)
 
-    def predict(self, X, **kwargs):
+    def predict(self, X: _DaskMatrixLike, **kwargs) -> dask_Array:
         """Docstring is inherited from the lightgbm.LGBMRegressor.predict."""
         return _predict(
             model=self.to_local(),
@@ -519,7 +580,7 @@ def predict(self, X, **kwargs):
 
     predict.__doc__ = LGBMRegressor.predict.__doc__
 
-    def to_local(self):
+    def to_local(self) -> LGBMRegressor:
         """Create regular version of lightgbm.LGBMRegressor from the distributed version.
 
         Returns
@@ -533,7 +594,16 @@ def to_local(self):
 class DaskLGBMRanker(LGBMRanker, _DaskLGBMModel):
     """Distributed version of lightgbm.LGBMRanker."""
 
-    def fit(self, X, y, sample_weight=None, init_score=None, group=None, client=None, **kwargs):
+    def fit(
+        self,
+        X: _DaskMatrixLike,
+        y: _DaskCollection,
+        sample_weight: Optional[_DaskCollection] = None,
+        init_score: Optional[_DaskCollection] = None,
+        group: Optional[_DaskCollection] = None,
+        client: Optional[Client] = None,
+        **kwargs: Any
+    ) -> "DaskLGBMRanker":
         """Docstring is inherited from the lightgbm.LGBMRanker.fit."""
         if init_score is not None:
             raise RuntimeError('init_score is not currently supported in lightgbm.dask')
@@ -555,13 +625,13 @@ def fit(self, X, y, sample_weight=None, init_score=None, group=None, client=None
                    + ' ' * 12 + 'Dask client.\n'
                    + ' ' * 8 + _eval_set + _after_eval_set)
 
-    def predict(self, X, **kwargs):
+    def predict(self, X: _DaskMatrixLike, **kwargs: Any) -> dask_Array:
         """Docstring is inherited from the lightgbm.LGBMRanker.predict."""
         return _predict(self.to_local(), X, **kwargs)
 
     predict.__doc__ = LGBMRanker.predict.__doc__
 
-    def to_local(self):
+    def to_local(self) -> LGBMRanker:
         """Create regular version of lightgbm.LGBMRanker from the distributed version.
 
         Returns