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BUG: pd.offsets.MonthEnd() delevers wrong month #49133

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BUG: pd.offsets.MonthEnd() delevers wrong month #49133

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336998e
Update offsets.pyx
jtimko16 Oct 16, 2022
fae682d
Clear whitespaces
jtimko16 Oct 17, 2022
2bf9a87
[DOCS] - Added more comment and examples of n parameter
jtimko16 Oct 17, 2022
e8552c2
Remove trailing white spaces
jtimko16 Oct 17, 2022
edcbdc1
Update pandas/_libs/tslibs/offsets.pyx
jtimko16 Oct 17, 2022
0e98b9f
Update pandas/_libs/tslibs/offsets.pyx
jtimko16 Oct 17, 2022
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46 changes: 46 additions & 0 deletions pandas/_libs/tslibs/offsets.pyx
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Expand Up @@ -2477,11 +2477,57 @@ cdef class MonthEnd(MonthOffset):
"""
DateOffset of one month end.

Parameters
----------
n : int, default 1
n = 0 -> offset to the end of month.
n = 1 -> depend on the given date:
a) Given date is on an anchor point (last day of the month) -> offset to the end of the following month.
b) Given date is not on an anchor point -> offset to the end of the same month.

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does this look right? can you try building this page of the docs to check please? https://pandas.pydata.org/docs/dev/development/contributing_documentation.html

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Ok, but I will need more time for this. I still have trouble with setting up virtual environment (spend one hour with it today and will continue tomorrow)

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@jtimko16 jtimko16 Oct 18, 2022 •
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What is the version of Python you are using? I created a virtual environment on top of Python 3.10, and trying to install packagse from requirements-dev.txt, however it always stuck at installation of boto3:
`

Using cached boto3-1.24.38-py3-none-any.whl (132 kB)
Using cached boto3-1.24.37-py3-none-any.whl (132 kB)
Using cached boto3-1.24.36-py3-none-any.whl (132 kB)
Using cached boto3-1.24.35-py3-none-any.whl (132 kB)
Using cached boto3-1.24.34-py3-none-any.whl (132 kB)
Using cached boto3-1.24.33-py3-none-any.whl (132 kB)
Using cached boto3-1.24.32-py3-none-any.whl (132 kB)`

Is it better to use older version of Python - e.g. 3.9? Thanks

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I'd suggest using mamba https://pandas.pydata.org/docs/dev/development/contributing_environment.html#option-1a-using-mamba-recommended

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please do ask (here or on Slack) if it's unclear / anything trips you up

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I tried to run it again, and also installed C++ Build Tools, but still receiving similar error. Please see below the full traceback:
Traceback_error.txt

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I don't know, sorry - you could ask on Slack , or try using Ubuntu via the WSL on Windows

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Hi, thank you. I don't want to sound like giving up. However unfortunately, this is going deeper and deeper technical, and I feel I am not able to effectively contribute. Is it OK, if I share the updated text of documentation in thread under the issue, and leave it for someone more technically capable to proceed with implementation?

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sure, that's fine, someone else can take this forwards, and if you feel like trying again, feel free to reach out and ask

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Ok, thanks. Maybe I will give it another go this weekend. Will let you know how I decide to proceed then. Thanks

Examples
--------
Offset to the end of the month:

>>> ts = pd.Timestamp(2022, 1, 1)
>>> ts + pd.offsets.MonthEnd()
Timestamp('2022-01-31 00:00:00')

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can you add a short sentence before the examples you've added to clarify what the reader is meant to take away from them? see https://pandas.pydata.org/docs/development/contributing_docstring.html#section-7-examples

However be careful, if given date is the last day of a month, method offsets to the end of the following month:

>>> ts = pd.Timestamp(2022, 1, 31)
>>> ts + pd.offsets.MonthEnd()
Timestamp('2022-02-28 00:00:00')

With the ``n`` parameter, we can control logic of offset.

See below, when ``n`` is set to 0, offset is always made to the end of the current month:

>>> ts = pd.Timestamp(2022, 1, 31)
>>> ts + pd.offsets.MonthEnd(n=0)
Timestamp('2022-01-31 00:00:00')

When ``n`` is set to 1 (default) it will be moved to the following month:

>>> ts = pd.Timestamp(2022, 1, 31)
>>> ts + pd.offsets.MonthEnd(n=1)
Timestamp('2022-02-28 00:00:00')

When ``n`` is set to 2, method offsets one additional month. And again depends whether given date is on an anchor point:

>>> ts = pd.Timestamp(2022, 1, 1)
>>> ts + pd.offsets.MonthEnd(n=2)
Timestamp('2022-02-28 00:00:00')

>>> ts = pd.Timestamp(2022, 1, 31)
>>> ts + pd.offsets.MonthEnd(n=2)
Timestamp('2022-03-31 00:00:00')

Also we can use negative ``n`` to find end of previous months:

>>> ts = pd.Timestamp(2022, 1, 31)
>>> ts + pd.offsets.MonthEnd(n=-1)
Timestamp('2021-12-31 00:00:00')
"""
_period_dtype_code = PeriodDtypeCode.M
_prefix = "M"
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