Add custom callable metric (#934)

* Add custom callable metric

* add custom tests

src/evidently/metrics/custom_metric.py

@@ -0,0 +1,51 @@
+from typing import Callable
+from typing import List
+from typing import Optional
+from typing import Union
+
+from pydantic import PrivateAttr
+
+from evidently.base_metric import InputData
+from evidently.base_metric import Metric
+from evidently.base_metric import MetricResult
+from evidently.model.widget import BaseWidgetInfo
+from evidently.options.base import AnyOptions
+from evidently.renderers.base_renderer import MetricRenderer
+from evidently.renderers.base_renderer import default_renderer
+from evidently.renderers.html_widgets import CounterData
+from evidently.renderers.html_widgets import counter
+
+
+class CustomCallableMetricResult(MetricResult):
+    value: float
+
+
+CustomCallableType = Callable[[InputData], float]
+
+
+class CustomCallableMetric(Metric[CustomCallableMetricResult]):
+    func: str
+    title: Optional[str] = None
+
+    _func: Optional[CustomCallableType] = PrivateAttr(None)
+
+    def __init__(self, func: Union[CustomCallableType, str], title: str = None, options: AnyOptions = None, **data):
+        if callable(func):
+            self._func = func
+            self.func = f"{func.__module__}.{func.__name__}"
+        else:
+            self._func = None
+            self.func = func
+        self.title = title
+        super().__init__(options, **data)
+
+    def calculate(self, data: InputData) -> CustomCallableMetricResult:
+        if self._func is None:
+            raise ValueError("CustomCallableMetric is not configured with callable func")
+        return CustomCallableMetricResult(value=self._func(data))
+
+
+@default_renderer(wrap_type=CustomCallableMetric)
+class CustomCallableMetricRenderer(MetricRenderer):
+    def render_html(self, obj: CustomCallableMetric) -> List[BaseWidgetInfo]:
+        return [counter(counters=[CounterData.float("", obj.get_result().value, 2)], title=obj.title or "")]

tests/multitest/metrics/conftest.py

@@ -102,7 +102,7 @@ def generate_dataset_outcome(m: TestMetric):
 
 
 def load_test_metrics():
-    for module in ["classification", "data_integrity", "data_drift", "data_quality", "recsys", "regression"]:
+    for module in ["classification", "data_integrity", "data_drift", "data_quality", "recsys", "regression", "custom"]:
         import_module(f"tests.multitest.metrics.{module}")
 
 

tests/multitest/metrics/custom.py

@@ -0,0 +1,26 @@
+import pandas as pd
+
+from evidently.base_metric import InputData
+from evidently.metrics.custom_metric import CustomCallableMetric
+from tests.multitest.conftest import AssertResultFields
+from tests.multitest.datasets import TestDataset
+from tests.multitest.metrics.conftest import TestMetric
+from tests.multitest.metrics.conftest import metric
+
+
+def custom_func(data: InputData) -> float:
+    return 0.3
+
+
+@metric
+def custom_callable_metric():
+    reference_data = current_data = pd.DataFrame({"text": [1, 2, 3]})
+
+    return TestMetric(
+        "custom_callable_metric",
+        CustomCallableMetric(func=custom_func, title="aaa"),
+        AssertResultFields({"value": 0.3}),
+        datasets=[
+            TestDataset("custom_callable_metric_data", current=current_data, reference=reference_data, tags=[]),
+        ],
+    )