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BUG: DatetimeIndex is_year_start breaks on BusinessMonthBegin frequency #58691
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BUG: DatetimeIndex is_year_start breaks on BusinessMonthBegin frequency #58691
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natmokval
commented
May 12, 2024
•
edited
edited
- closes BUG: DatetimeIndex.is_year_start breaks on BusinessMonthBegin frequency #58729
- Tests added and passed
- Added an entry in the latest `doc/source/whatsnew/v3.0.0.rst
Thanks @natmokval for the PR. Should the OP be an issue instead.? or is there already an open issue for this? |
thanks @simonjayhawkins for the comment. No, there is no open issue for this. |
…eq-BusinessMonthStart
Fixed bug in |
thanks for looking into this not sure this fixes the issue to be honest: In [2]: pd.DatetimeIndex(['1976-11-01', '1976-12-01', '1977-01-03'], freq='BMS')
Out[2]: DatetimeIndex(['1976-11-01', '1976-12-01', '1977-01-03'], dtype='datetime64[s]', freq='BMS')
In [3]: arr = pd.DatetimeIndex(['1976-11-01', '1976-12-01', '1977-01-03'], freq='BMS')
In [4]: arr.is_year_start
Out[4]: array([False, False, True])
In [5]: [x.is_year_start for x in arr]
Out[5]: [False, False, False] We'd expect Here's a little hypothesis test I put together: import pytest
import hypothesis.strategies as st
from hypothesis import given
import pandas as pd
from datetime import datetime
@pytest.mark.parametrize('freq', [
'MS',
'BMS',
])
@given(dt = st.datetimes(min_value=datetime(1960, 1, 1), max_value=datetime(1980, 1, 1)))
def test_me(freq, dt):
d = pd.date_range(dt, periods=3, freq=freq)
result = [x for x in d.is_year_start]
expected = [x.is_year_start for x in d]
assert result == expected Granted, it looks like this is already super-broken on |
Sorry, as an addendum to my previous comment: If I amend the hypothesis test to be: @given(
dt = st.datetimes(min_value=datetime(1960, 1, 1), max_value=datetime(1980, 1, 1)),
n = st.integers(min_value=1, max_value=10),
freq = st.sampled_from(['BMS'])
)
def test_me(freq, dt, n):
freq = f'{n}{freq}'
d = pd.date_range(dt, periods=3, freq=freq)
result = [x for x in d.is_year_start]
expected = []
for x in d:
if x.is_year_start:
expected.append(True)
else:
if x.day_of_week == 0 and (x - pd.Timedelta(days=1)).is_year_start:
expected.append(True)
elif x.day_of_week == 0 and (x - pd.Timedelta(days=2)).is_year_start:
expected.append(True)
else:
expected.append(False)
assert result == expected then it does indeed pass I think we should get #57494 in first though, as I think that that also fixes the issues "for free" (but then we keep the test from this one) |