fix nonetype error during print for tasks without class labels (#1148)

* fix nonetype error during print for tasks without class labels

* fix #1100/#1058 nonetype error

Co-authored-by: Pieter Gijsbers <p.gijsbers@tue.nl>

Author: willcmartin

doc/progress.rst

@@ -8,11 +8,12 @@ Changelog
 
 0.13.0
 ~~~~~~
- * MAINT#1104: Fix outdated docstring for ``list_task``.
  * FIX#1030: ``pre-commit`` hooks now no longer should issue a warning.
+ * FIX#1058, #1100: Avoid ``NoneType`` error when printing task without ``class_labels`` attribute.
  * FIX#1110: Make arguments to ``create_study`` and ``create_suite`` that are defined as optional by the OpenML XSD actually optional.
  * FIX#1147: ``openml.flow.flow_exists`` no longer requires an API key.
  * MAIN#1088: Do CI for Windows on Github Actions instead of Appveyor.
+ * MAINT#1104: Fix outdated docstring for ``list_task``.
  * MAIN#1146: Update the pre-commit dependencies.
  * ADD#1103: Add a ``predictions`` property to OpenMLRun for easy accessibility of prediction data.
 

openml/tasks/task.py

@@ -97,7 +97,7 @@ def _get_repr_body_fields(self) -> List[Tuple[str, Union[str, int, List[str]]]]:
             fields["Estimation Procedure"] = self.estimation_procedure["type"]
         if getattr(self, "target_name", None) is not None:
             fields["Target Feature"] = getattr(self, "target_name")
-            if hasattr(self, "class_labels"):
+            if hasattr(self, "class_labels") and getattr(self, "class_labels") is not None:
                 fields["# of Classes"] = len(getattr(self, "class_labels"))
             if hasattr(self, "cost_matrix"):
                 fields["Cost Matrix"] = "Available"