BUG: generated timestamps deviate from expected values · Issue #48255 · pandas-dev/pandas (original) (raw)

Pandas version checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of pandas.
• I have confirmed this bug DOES NOT exist on the main branch of pandas (1.4.3 at the time of creating this Issue).

Reproducible Example

import pandas as pd import db_dtypes

value = "23:59:59.999999" expected = datetime.time(23, 59, 59, 999999)

def test_time_parsing(value, expected): assert pandas.Series([value], dtype="dbtime")[0] == expected

The results of the above assert are:

assert datetime.time(23, 59, 58, 999271) == datetime.time(23, 59, 59, 999999)

Issue Description

Formatted time strings are incorrectly converted to datetime.time objects.

When running the prerelease tests for python-db-dtypes-pandas and checking for prerelease issues that might be associated with the pandas dev branches, we found identified that several python-db-dtypes-pandas tests failed depending on which nightly pandas branch we use.

In particular between these two commits:

• b74dc5c077 yields PASSING TESTS
• 87da50042c yields FAILING TESTS

Not sure yet if this is due to something that derives from the python-db-dtypes-pandas lib OR from pandas OR from one of pandas' dependencies.

NOTE: the reproducible example provided is just one of many tests in the test suite that fail with a wide variety of different times, etc.

Expected Behavior

The expected result of the reproducible example should be:

assert datetime.time(23, 59, 59, 999999) == datetime.time(23, 59, 59, 999999)

Installed Versions

For reference here are the installed libraries when we ran these tests. When running the failing tests, the only package that changed was the version of pandas. All other packages were the same:

python==3.10
# >>>>>>>>>>>>>>>>>>>>>>
asttokens==2.0.8
asyncmock==0.4.2
attrs==22.1.0
backcall==0.2.0
coverage==6.4.4
-e git+ssh://git@github.com/googleapis/python-db-dtypes-pandas.git@23d88d9e843e903a6e5a123123825de1bd88c722#egg=db_dtypes
decorator==5.1.1
executing==0.10.0
iniconfig==1.1.1
ipython==8.4.0
jedi==0.18.1
matplotlib-inline==0.1.6
mock==4.0.3
numpy==1.23.2
packaging==21.3
pandas==1.5.0.dev0+686.g5b76b77399  # A passing version of pandas
parso==0.8.3
pexpect==4.8.0
pickleshare==0.7.5
pluggy==1.0.0
prompt-toolkit==3.0.30
ptyprocess==0.7.0
pure-eval==0.2.2
py==1.11.0
pyarrow==9.0.0
Pygments==2.13.0
pyparsing==3.0.9
pytest==7.1.2
pytest-asyncio==0.19.0
pytest-cov==3.0.0
python-dateutil==2.8.2
pytz==2022.2.1
six==1.16.0
stack-data==0.4.0
tomli==2.0.1
traitlets==5.3.0
wcwidth==0.2.5