Predictions (openml#1128)

* Add easy way to retrieve run predictions

* Log addition of ``predictions`` (openml#1103)

doc/progress.rst

@@ -11,7 +11,7 @@ Changelog
  * FIX#1030: ``pre-commit`` hooks now no longer should issue a warning.
  * FIX#1110: Make arguments to ``create_study`` and ``create_suite`` that are defined as optional by the OpenML XSD actually optional.
  * MAIN#1088: Do CI for Windows on Github Actions instead of Appveyor.
-
+ * ADD#1103: Add a ``predictions`` property to OpenMLRun for easy accessibility of prediction data.
 
 
 0.12.2

openml/runs/run.py

@@ -8,6 +8,7 @@
 
 import arff
 import numpy as np
+import pandas as pd
 
 import openml
 import openml._api_calls
@@ -116,6 +117,23 @@ def __init__(
         self.predictions_url = predictions_url
         self.description_text = description_text
         self.run_details = run_details
+        self._predictions = None
+
+    @property
+    def predictions(self) -> pd.DataFrame:
+        """ Return a DataFrame with predictions for this run """
+        if self._predictions is None:
+            if self.data_content:
+                arff_dict = self._generate_arff_dict()
+            elif self.predictions_url:
+                arff_text = openml._api_calls._download_text_file(self.predictions_url)
+                arff_dict = arff.loads(arff_text)
+            else:
+                raise RuntimeError("Run has no predictions.")
+            self._predictions = pd.DataFrame(
+                arff_dict["data"], columns=[name for name, _ in arff_dict["attributes"]]
+            )
+        return self._predictions
 
     @property
     def id(self) -> Optional[int]:

tests/test_runs/test_run_functions.py

@@ -180,6 +180,7 @@ def _rerun_model_and_compare_predictions(self, run_id, model_prime, seed, create
         predictions_prime = run_prime._generate_arff_dict()
 
         self._compare_predictions(predictions, predictions_prime)
+        pd.testing.assert_frame_equal(run.predictions, run_prime.predictions)
 
     def _perform_run(
         self,