Issue 35 metadata lost on multiplication (#43)

This PR adds no additional logic, only a test to check whether Issue #35 is successfully resolved (plus some refactoring of test util functions). Note that this is a merge into resample-while-keeping-metadata, and that branch (with PR #23) actually contains the logic that resolves this issue (as a side effect, because I was actually addressing deeper issues there: #22 and #26).

* Refactor metadata propagation checks to util function.

* Add test for metadata propagation upon multiplication (GH 35).

Co-authored-by: F.N. Claessen <[email protected]>

timely_beliefs/tests/test_belief_io.py

@@ -7,8 +7,8 @@
 import pytz
 
 import timely_beliefs as tb
-from timely_beliefs.beliefs.classes import METADATA
 from timely_beliefs.examples import example_df
+from timely_beliefs.tests.utils import assert_metadata_is_retained
 
 
 @pytest.fixture(scope="module")
@@ -360,21 +360,16 @@ def test_converting_between_data_frame_and_series_retains_metadata():
     Test whether expanding dimensions of a BeliefsSeries into a BeliefsDataFrame retains the metadata.
     """
     df = example_df
-    metadata = {md: getattr(example_df, md) for md in METADATA}
     series = df["event_value"]
-    for md in metadata:
-        assert getattr(series, md) == metadata[md]
+    assert_metadata_is_retained(series, original_df=example_df, is_series=True)
     df = series.to_frame()
-    for md in metadata:
-        assert getattr(df, md) == metadata[md]
+    assert_metadata_is_retained(df, original_df=example_df)
 
 
 def test_dropping_index_levels_retains_metadata():
     df = example_df.copy()
-    metadata = {md: getattr(example_df, md) for md in METADATA}
     df.index = df.index.get_level_values("event_start")  # drop all other index levels
-    for md in metadata:
-        assert getattr(df, md) == metadata[md]
+    assert_metadata_is_retained(df, original_df=example_df)
 
 
 @pytest.mark.parametrize("drop_level", [True, False])
@@ -383,12 +378,9 @@ def test_slicing_retains_metadata(drop_level):
     Test whether slicing the index of a BeliefsDataFrame retains the metadata.
     """
     df = example_df
-    metadata = {md: getattr(example_df, md) for md in METADATA}
     df = df.xs("2000-01-03 10:00:00+00:00", level="event_start", drop_level=drop_level)
     print(df)
-    assert isinstance(df, tb.BeliefsDataFrame)
-    for md in metadata:
-        assert getattr(df, md) == metadata[md]
+    assert_metadata_is_retained(df, original_df=example_df)
 
 
 @pytest.mark.parametrize("resolution", [timedelta(minutes=30), timedelta(hours=2)])
@@ -400,15 +392,13 @@ def test_mean_resampling_retains_metadata(resolution):
     Succeeds with pandas==1.1.0
     """
     df = example_df
-    metadata = {md: getattr(example_df, md) for md in METADATA}
     df = df.resample(resolution, level="event_start").mean()
     print(df)
-    assert isinstance(df, tb.BeliefsDataFrame)
-    for md in metadata:
-        # if md == "event_resolution":
-        #     assert df.event_resolution == resolution
-        # else:  # todo: the event_resolution metadata is only updated when resampling using df.resample_events(). A reason to override the original resample method, or otherwise something to document.
-        assert getattr(df, md) == metadata[md]
+    assert_metadata_is_retained(
+        df,
+        original_df=example_df,
+        event_resolution=example_df.event_resolution,
+    )  # todo: the event_resolution metadata is only updated when resampling using df.resample_events(). A reason to override the original resample method, or otherwise something to document.
 
 
 @pytest.mark.parametrize("resolution", [timedelta(minutes=30), timedelta(hours=2)])
@@ -419,7 +409,6 @@ def _test_agg_resampling_retains_metadata(resolution):
     Fails with pandas==1.1.5
     """
     df = example_df
-    metadata = {md: getattr(example_df, md) for md in METADATA}
     df = df.reset_index(level=["belief_time", "source", "cumulative_probability"])
     df = df.resample(resolution).agg(
         {
@@ -431,12 +420,11 @@ def _test_agg_resampling_retains_metadata(resolution):
     )
     df = df.set_index(["belief_time", "source", "cumulative_probability"], append=True)
     print(df)
-    assert isinstance(df, tb.BeliefsDataFrame)
-    for md in metadata:
-        # if md == "event_resolution":
-        #     assert df.event_resolution == resolution
-        # else:  # todo: the event_resolution metadata is only updated when resampling using df.resample_events(). A reason to override the original resample method, or otherwise something to document.
-        assert getattr(df, md) == metadata[md]
+    assert_metadata_is_retained(
+        df,
+        original_df=example_df,
+        event_resolution=example_df.event_resolution,
+    )  # todo: the event_resolution metadata is only updated when resampling using df.resample_events(). A reason to override the original resample method, or otherwise something to document.
 
 
 def test_groupby_retains_metadata():
@@ -447,19 +435,14 @@ def test_groupby_retains_metadata():
     Fixed with pandas==1.1.5
     """
     df = example_df
-    metadata = {md: getattr(example_df, md) for md in METADATA}
 
     def assert_function(x):
         print(x)
-        assert isinstance(x, tb.BeliefsDataFrame)
-        for md in metadata:
-            assert getattr(x, md) == metadata[md]
+        assert_metadata_is_retained(x, original_df=example_df)
         return x
 
     df = df.groupby(level="event_start").apply(lambda x: assert_function(x))
-    assert isinstance(df, tb.BeliefsDataFrame)
-    for md in metadata:
-        assert getattr(df, md) == metadata[md]
+    assert_metadata_is_retained(df, original_df=example_df)
 
 
 def test_copy_series_retains_name_and_metadata():
@@ -589,3 +572,19 @@ def _constructor_sliced(self):
     df2 = getattr(df.groupby("x"), att)(*args)
     print(df2)
     assert df2.a == "b"
+
+
+@pytest.mark.parametrize("constant", [1, -1, 3.14, timedelta(hours=1), ["TiledString"]])
+def test_multiplication_with_constant_retains_metadata(constant):
+    """ Check whether the metadata is still there after multiplication. """
+    # GH 35
+    df = example_df * constant
+    assert_metadata_is_retained(df, original_df=example_df)
+
+    # Also check suggested workarounds from GH 35
+    if constant == -1:
+        df = -example_df
+        assert_metadata_is_retained(df, original_df=example_df)
+
+        df = example_df.abs()
+        assert_metadata_is_retained(df, original_df=example_df)

timely_beliefs/tests/utils.py

@@ -1,7 +1,37 @@
-from typing import Union
+from datetime import timedelta
+from typing import Optional, Union
 
 import numpy as np
 
+import timely_beliefs as tb
+from timely_beliefs.beliefs.classes import METADATA
+
 
 def equal_lists(list_a: Union[list, np.ndarray], list_b: Union[list, np.ndarray]):
     return all(np.isclose(a, b) for a, b in zip(list_a, list_b))
+
+
+def assert_metadata_is_retained(
+    result_df: Union[tb.BeliefsDataFrame, tb.BeliefsSeries],
+    original_df: tb.BeliefsDataFrame,
+    is_series: bool = False,
+    event_resolution: Optional[timedelta] = None,
+):
+    """Fail if result_df is not a BeliefsDataFrame with the same metadata as the original BeliefsDataFrame.
+
+    Can also be used to check for a BeliefsSeries (using is_series=True).
+
+    :param result_df: BeliefsDataFrame or BeliefsSeries to be checked for metadata propagation
+    :param original_df: BeliefsDataFrame containing the original metadata
+    :param is_series: if True, we check that the result is a BeliefsSeries rather than a BeliefsDataFrame
+    :param event_resolution: optional timedelta in case we expect a different event_resolution than the original
+    """
+    metadata = {md: getattr(original_df, md) for md in METADATA}
+    assert isinstance(
+        result_df, tb.BeliefsDataFrame if not is_series else tb.BeliefsSeries
+    )
+    for md in metadata:
+        if md == "event_resolution" and event_resolution is not None:
+            assert result_df.event_resolution == event_resolution
+        else:
+            assert getattr(result_df, md) == metadata[md]