api: exp_show: Postprocess empty strings as None.

Makes it easier to manipulate when converting to pandas DataFrame.

dvc/api/experiments.py

@@ -83,6 +83,10 @@ def _postprocess(exp_rows):
                     exp_row[k] = float(v_str)
                 except ValueError:
                     exp_row[k] = v_str
+
+            if not exp_row[k]:
+                exp_row[k] = None
+
     return exp_rows
 
 

tests/func/api/test_experiments.py

@@ -30,3 +30,5 @@ def test_exp_show(tmp_dir, dvc, scm, exp_stage):  # noqa: F811
     assert exps[0]["metrics.yaml:foo"] == 1.0
     # Postprocessing using `None` as fill value
     assert exps[0]["State"] is None
+    # Postprocessing empty string as `None`
+    assert exps[0]["Experiment"] is None