feat: feature selector (#17)

* feat: feature-selector

* unit tests

* docs update

* bump version

README.md

@@ -20,7 +20,7 @@ How can you use it?
 smith forge
 ```
 
-🚧 As a TUI (terminal user interface): Working in progress!
+🚧 As a TUI (terminal user interface): Work in progress!
 
 All these tools will prompt a series of questions regarding the estimator you want to create, and then it will generate the boilerplate code for you.
 
@@ -66,6 +66,17 @@ and it should be compatible with scikit-learn Pipeline, GridSearchCV, etc.
 Scikit-learn documentation on how to
 [develop estimators](https://scikit-learn.org/dev/developers/develop.html#developing-scikit-learn-estimators).
 
+## Supported estimators
+
+The following types of scikit-learn estimator are supported:
+
+- Classifier
+- Regressor
+- Transformer
+  - Feature Selector
+- Outlier Detector
+- Clusterer
+
 ## Installation
 
 sklearn-smithy is available on [pypi](https://pypi.org/project/sklearn-smithy), so you can install it directly from there:

docs/index.md

@@ -13,10 +13,21 @@ How can you use it?
     smith forge
     ```
 
-- [ ] As a TUI (terminal user interface): [Working in progress](https://github.com/FBruzzesi/sklearn-smithy/issues/1)!
+- [ ] As a TUI (terminal user interface): [Work in progress](https://github.com/FBruzzesi/sklearn-smithy/issues/1)!
 
 All these tools will prompt a series of questions regarding the estimator you want to create, and then it will generate the boilerplate code for you.
 
+## Supported estimators
+
+The following types of scikit-learn estimator are supported:
+
+- Classifier
+- Regressor
+- Transformer
+  - Feature Selector
+- Outlier Detector
+- Clusterer
+
 ## Origin story
 
 The idea for this tool originated from [scikit-lego #660](https://github.com/koaning/scikit-lego/pull/660){:target="_blank"}, which I cannot better explain than quoting the PR description itself:

docs/user-guide.md

@@ -28,14 +28,14 @@ Let's see an example of how to use `smith forge` command:
 ```console
 $ <font color="#4E9A06">smith</font> forge
 # 🐍 How would you like to name the estimator?:$ MightyClassifier
-# 🎯 Which kind of estimator is it? (classifier, outlier, regressor, transformer, cluster):$ classifier
+# 🎯 Which kind of estimator is it? (classifier, outlier, regressor, transformer, cluster, feature-selector):$ classifier
 # 📜 Please list the required parameters (comma-separated) []:$ alpha,beta
 # 📑 Please list the optional parameters (comma-separated) []:$ mu,sigma
 # 📶 Does the `.fit()` method support `sample_weight`? [y/N]:$ y
 # 📏 Is the estimator linear? [y/N]:$ N
 # 🎲 Should the estimator implement a `predict_proba` method? [y/N]:$ N
 # ❓ Should the estimator implement a `decision_function` method? [y/N]:$ y
-# 🧪 We are almost there... Is there any tag you want to add? (comma-separated) []:$ binary_only
+# 🧪 We are almost there... Is there any tag you want to add? (comma-separated) []:$ binary_only,non_deterministic
 # 📂 Where would you like to save the class? [mightyclassifier.py]:$ path/to/file.py
 <span style="color: green; font-weight: bold;">Template forged at path/to/file.py </span>
 ```

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "sklearn-smithy"
-version = "0.0.9"
+version = "0.0.10"
 description = "Toolkit to forge scikit-learn compatible estimators."
 requires-python = ">=3.10"
 

sksmithy/_models.py

@@ -13,6 +13,7 @@ class EstimatorType(str, Enum):
     RegressorMixin = "regressor"
     TransformerMixin = "transformer"
     ClusterMixin = "cluster"
+    SelectorMixin = "feature-selector"
 
 
 class TagType(str, Enum):

sksmithy/app.py

@@ -124,7 +124,7 @@
         estimator = st.selectbox(
             label=PROMPT_ESTIMATOR,
             options=tuple(e.value for e in EstimatorType),
-            format_func=lambda x: x.capitalize(),
+            format_func=lambda v: " ".join(x.capitalize() for x in v.split("-")),
             index=None,
             key="estimator",
         )

sksmithy/template.py.jinja

@@ -1,4 +1,4 @@
-{%- if estimator_type=='classifier' %}
+{%- if estimator_type in ('classifier', 'feature-selector') %}
 import numpy as np
 {% endif -%}
 {%- if estimator_type == 'classifier' and linear %}
@@ -7,6 +7,9 @@ from sklearn.linear_model._base import LinearClassifierMixin
 {% elif estimator_type == 'regressor' and linear%}
 from sklearn.base import {{ mixin }}
 from sklearn.linear_model._base import LinearModel
+{% elif estimator_type == 'feature-selector'%}
+from sklearn.base import BaseEstimator
+from sklearn.feature_selection import SelectorMixin
 {% else %}
 from sklearn.base import BaseEstimator, {{ mixin }}
 {% endif -%}
@@ -56,7 +59,7 @@ class {{ name }}(
         {% endfor -%}
         {% endif %}
 
-    def fit(self, X, y{% if estimator_type == 'transformer' %}=None{% endif %}{% if sample_weight %}, sample_weight=None{% endif %}):
+    def fit(self, X, y{% if estimator_type in ('transformer', 'feature-selector') %}=None{% endif %}{% if sample_weight %}, sample_weight=None{% endif %}):
         """
         Fit {{name}} estimator.
 
@@ -82,7 +85,7 @@ class {{ name }}(
         self : {{name}}
             Fitted {{name}} estimator.
         """
-        {%- if estimator_type == 'transformer' %}
+        {%- if estimator_type in ('transformer', 'feature-selector') %}
         X = check_array(X, ...) #TODO: Fill in `check_array` arguments
         {% else %}
         X, y = check_X_y(X, y, ...) #TODO: Fill in `check_X_y` arguments
@@ -105,6 +108,13 @@ class {{ name }}(
         {% if 'max_iter' in parameters -%}self.n_iter_ = ...{%- endif %}
         {% if estimator_type=='outlier' -%}self.offset_ = ...{%- endif %}
         {% if estimator_type=='cluster' -%}self.labels_ = ...{%- endif %}
+        {% if estimator_type=='feature-selector'%}
+        self.selected_features_ = ...  # TODO: Indexes of selected features
+        self.support_ = np.isin(
+            np.arange(0, self.n_features_in_),  # all_features
+            self.selected_features_
+        )
+        {%- endif %}
 
         return self
 
@@ -255,6 +265,20 @@ class {{ name }}(
         return X_ts
     {%- endif %}
 
+    {% if estimator_type=='feature-selector' -%}
+    def _get_support_mask(self, X):
+        """Get the boolean mask indicating which features are selected.
+
+        Returns
+        -------
+        support : boolean array of shape [# input features]
+            An element is True iff its corresponding feature is selected for retention.
+        """
+
+        check_is_fitted(self)
+        return self.support_
+    {%- endif %}
+
     {% if tags %}
     def _more_tags(self):
         return {

tests/test_render.py

@@ -65,7 +65,7 @@ def test_common_estimator(name: str, estimator: EstimatorType, sample_weight: bo
     assert ("sample_weight = _check_sample_weight(sample_weight)" in result) == sample_weight
 
     match estimator:
-        case EstimatorType.TransformerMixin:
+        case EstimatorType.TransformerMixin | EstimatorType.SelectorMixin:
             assert "X = check_array(X, ...)" in result
             assert ("def fit(self, X, y=None, sample_weight=None)" in result) == (sample_weight)
             assert ("def fit(self, X, y=None)" in result) == (not sample_weight)
@@ -191,6 +191,28 @@ def test_transformer(name: str) -> None:
     assert "def predict(self, X)" not in result
 
 
+def test_feature_selector(name: str) -> None:
+    """Tests transformer specific rendering."""
+    estimator_type = EstimatorType.SelectorMixin
+
+    result = render_template(
+        name=name,
+        estimator_type=estimator_type,
+        required=[],
+        optional=[],
+        sample_weight=False,
+        linear=False,
+        predict_proba=False,
+        decision_function=False,
+        tags=None,
+    )
+    # Transformer specific
+    assert "class MightyEstimator(SelectorMixin, BaseEstimator)" in result
+    assert "def _get_support_mask(self, X)" in result
+    assert "self.support_" in result
+    assert "def predict(self, X)" not in result
+
+
 def test_cluster(name: str) -> None:
     """Tests cluster specific rendering."""
     estimator_type = EstimatorType.ClusterMixin