fix: avoid rounding problems with microseconds

db_dtypes/__init__.py

@@ -69,29 +69,33 @@ def _datetime(
         cls,
         scalar,
         match_fn=re.compile(
-            r"\s*(?P<hour>\d+)(?::(?P<minute>\d+)(?::(?P<second>\d+(?:[.]\d+)?)?)?)?\s*$"
+            r"\s*(?P<hours>\d+)"
+            r"(?::(?P<minutes>\d+)"
+            r"(?::(?P<seconds>\d+)"
+            r"(?:\.(?P<fraction>\d*))?)?)?\s*$"
         ).match,
     ):
         if isinstance(scalar, datetime.time):
             return datetime.datetime.combine(cls._epoch, scalar)
         elif isinstance(scalar, str):
             # iso string
-            match = match_fn(scalar)
-            if not match:
+            parsed = match_fn(scalar)
+            if not parsed:
                 raise ValueError(f"Bad time string: {repr(scalar)}")
 
-            hour = match.group("hour")
-            minute = match.group("minute")
-            second = match.group("second")
-            second, microsecond = divmod(float(second if second else 0), 1)
+            hours = parsed.group("hours")
+            minutes = parsed.group("minutes")
+            seconds = parsed.group("seconds")
+            fraction = parsed.group("fraction")
+            microseconds = int(fraction.ljust(6, "0")[:6]) if fraction else 0
             return datetime.datetime(
                 1970,
                 1,
                 1,
-                int(hour),
-                int(minute if minute else 0),
-                int(second),
-                int(microsecond * 1_000_000),
+                int(hours),
+                int(minutes) if minutes else 0,
+                int(seconds) if seconds else 0,
+                microseconds,
             )
         else:
             raise TypeError("Invalid value type", scalar)

tests/unit/test_date.py

@@ -0,0 +1,62 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import datetime
+
+import pandas
+import pytest
+
+# To register the types.
+import db_dtypes  # noqa
+
+
+@pytest.mark.parametrize(
+    "value, expected",
+    [
+        # Min/Max values for pandas.Timestamp.
+        ("1677-09-22", datetime.date(1677, 9, 22)),
+        ("2262-04-11", datetime.date(2262, 4, 11)),
+        # Typical "zero" values.
+        ("1900-01-01", datetime.date(1900, 1, 1)),
+        ("1970-01-01", datetime.date(1970, 1, 1)),
+        # Assorted values.
+        ("1993-10-31", datetime.date(1993, 10, 31)),
+        ("2012-02-29", datetime.date(2012, 2, 29)),
+        ("2021-12-17", datetime.date(2021, 12, 17)),
+        ("2038-01-19", datetime.date(2038, 1, 19)),
+    ],
+)
+def test_date_parsing(value, expected):
+    assert pandas.Series([value], dtype="date")[0] == expected
+
+
+@pytest.mark.parametrize(
+    "value, error",
+    [
+        ("thursday", "Bad date string: 'thursday'"),
+        ("1-2-thursday", "Bad date string: '1-2-thursday'"),
+        ("1-2-3-4", "Bad date string: '1-2-3-4'"),
+        ("1-2-3.f", "Bad date string: '1-2-3.f'"),
+        ("1-d-3", "Bad date string: '1-d-3'"),
+        ("1-3", "Bad date string: '1-3'"),
+        ("1", "Bad date string: '1'"),
+        ("", "Bad date string: ''"),
+        ("2021-2-99", "day is out of range for month"),
+        ("2021-99-1", "month must be in 1[.][.]12"),
+        ("10000-1-1", "year 10000 is out of range"),
+    ],
+)
+def test_date_parsing_errors(value, error):
+    with pytest.raises(ValueError, match=error):
+        pandas.Series([value], dtype="date")

tests/unit/test_dtypes.py

@@ -621,51 +621,3 @@ def test_date_sub():
     do = pd.Series([pd.DateOffset(days=i) for i in range(4)])
     expect = dates.astype("object") - do
     assert np.array_equal(dates - do, expect)
-
-
-@pytest.mark.parametrize(
-    "value, expected", [("1", datetime.time(1)), ("1:2", datetime.time(1, 2))],
-)
-def test_short_time_parsing(value, expected):
-    assert _cls("time")([value])[0] == expected
-
-
-@pytest.mark.parametrize(
-    "value, error",
-    [
-        ("thursday", "Bad time string: 'thursday'"),
-        ("1:2:3thursday", "Bad time string: '1:2:3thursday'"),
-        ("1:2:3:4", "Bad time string: '1:2:3:4'"),
-        ("1:2:3.f", "Bad time string: '1:2:3.f'"),
-        ("1:d:3", "Bad time string: '1:d:3'"),
-        ("1:2.3", "Bad time string: '1:2.3'"),
-        ("", "Bad time string: ''"),
-        ("1:2:99", "second must be in 0[.][.]59"),
-        ("1:99", "minute must be in 0[.][.]59"),
-        ("99", "hour must be in 0[.][.]23"),
-    ],
-)
-def test_bad_time_parsing(value, error):
-    with pytest.raises(ValueError, match=error):
-        _cls("time")([value])
-
-
-@pytest.mark.parametrize(
-    "value, error",
-    [
-        ("thursday", "Bad date string: 'thursday'"),
-        ("1-2-thursday", "Bad date string: '1-2-thursday'"),
-        ("1-2-3-4", "Bad date string: '1-2-3-4'"),
-        ("1-2-3.f", "Bad date string: '1-2-3.f'"),
-        ("1-d-3", "Bad date string: '1-d-3'"),
-        ("1-3", "Bad date string: '1-3'"),
-        ("1", "Bad date string: '1'"),
-        ("", "Bad date string: ''"),
-        ("2021-2-99", "day is out of range for month"),
-        ("2021-99-1", "month must be in 1[.][.]12"),
-        ("10000-1-1", "year 10000 is out of range"),
-    ],
-)
-def test_bad_date_parsing(value, error):
-    with pytest.raises(ValueError, match=error):
-        _cls("date")([value])

tests/unit/test_time.py

@@ -0,0 +1,84 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import datetime
+
+import pandas
+import pytest
+
+# To register the types.
+import db_dtypes  # noqa
+
+
+@pytest.mark.parametrize(
+    "value, expected",
+    [
+        # Midnight
+        ("0", datetime.time(0)),
+        ("0:0", datetime.time(0)),
+        ("0:0:0", datetime.time(0)),
+        ("0:0:0.", datetime.time(0)),
+        ("0:0:0.0", datetime.time(0)),
+        ("0:0:0.000000", datetime.time(0)),
+        ("00:00:00", datetime.time(0, 0, 0)),
+        ("  00:00:00  ", datetime.time(0, 0, 0)),
+        # Short values
+        ("1", datetime.time(1)),
+        ("23", datetime.time(23)),
+        ("1:2", datetime.time(1, 2)),
+        ("23:59", datetime.time(23, 59)),
+        ("1:2:3", datetime.time(1, 2, 3)),
+        ("23:59:59", datetime.time(23, 59, 59)),
+        # Non-octal values.
+        ("08:08:08", datetime.time(8, 8, 8)),
+        ("09:09:09", datetime.time(9, 9, 9)),
+        # Fractional seconds can cause rounding problems if cast to float. See:
+        # https://github.com/googleapis/python-db-dtypes-pandas/issues/18
+        ("0:0:59.876543", datetime.time(0, 0, 59, 876543)),
+        ("01:01:01.010101", datetime.time(1, 1, 1, 10101)),
+        ("09:09:09.090909", datetime.time(9, 9, 9, 90909)),
+        ("11:11:11.111111", datetime.time(11, 11, 11, 111111)),
+        ("19:16:23.987654", datetime.time(19, 16, 23, 987654)),
+        # Microsecond precision
+        ("00:00:00.000001", datetime.time(0, 0, 0, 1)),
+        ("23:59:59.999999", datetime.time(23, 59, 59, 999_999)),
+        # TODO: Support nanosecond precision values without truncation.
+        # https://github.com/googleapis/python-db-dtypes-pandas/issues/19
+        ("0:0:0.000001001", datetime.time(0, 0, 0, 1)),
+        ("23:59:59.999999000", datetime.time(23, 59, 59, 999_999)),
+        ("23:59:59.999999999", datetime.time(23, 59, 59, 999_999)),
+    ],
+)
+def test_time_parsing(value, expected):
+    assert pandas.Series([value], dtype="time")[0] == expected
+
+
+@pytest.mark.parametrize(
+    "value, error",
+    [
+        ("thursday", "Bad time string: 'thursday'"),
+        ("1:2:3thursday", "Bad time string: '1:2:3thursday'"),
+        ("1:2:3:4", "Bad time string: '1:2:3:4'"),
+        ("1:2:3.f", "Bad time string: '1:2:3.f'"),
+        ("1:d:3", "Bad time string: '1:d:3'"),
+        ("1:2.3", "Bad time string: '1:2.3'"),
+        ("", "Bad time string: ''"),
+        ("1:2:99", "second must be in 0[.][.]59"),
+        ("1:99", "minute must be in 0[.][.]59"),
+        ("99", "hour must be in 0[.][.]23"),
+    ],
+)
+def test_time_parsing_errors(value, error):
+    with pytest.raises(ValueError, match=error):
+        pandas.Series([value], dtype="time")