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Inconsistent behavior of *_range functions #17471

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jschendel opened this issue Sep 8, 2017 · 1 comment

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commented Sep 8, 2017

Currently there are some inconsistencies in behavior between the various *_range functions: date_range, period_range, timedelta_range, interval_range.

Note: bdate_range and cdate_range largely use the same code as date_range, so I'm lumping the behavior all three together in the examples below.

End Inclusion

The end parameter of interval_range is not included in the resulting IntervalIndex:

In [2]: pd.interval_range(start=0, end=4)
Out[2]:
IntervalIndex([(0, 1], (1, 2], (2, 3]]
              closed='right',
              dtype='interval[int64]')

However, end is included in the output of the other *_range functions:

In [3]: pd.period_range(start='2017Q1', end='2017Q4', freq='Q')
Out[3]: PeriodIndex(['2017Q1', '2017Q2', '2017Q3', '2017Q4'], dtype='period[Q-DEC]', freq='Q-DEC')

In [4]: pd.date_range(start='2017-01-01', end='2017-01-04')
Out[4]: DatetimeIndex(['2017-01-01', '2017-01-02', '2017-01-03', '2017-01-04'], dtype='datetime64[ns]', freq='D')

In [5]: pd.timedelta_range(start='1 day', end='4 days')
Out[5]: TimedeltaIndex(['1 days', '2 days', '3 days', '4 days'], dtype='timedelta64[ns]', freq='D')

Proposal: interval_range should include end as the endpoint of the last interval in the resulting IntervalIndex.

Behavior when too many parameters are passed

When the start, end, and periods parameters are all passed, interval_range ignores the periods parameter:

In [6]: pd.interval_range(start=0, end=4, periods=6)
Out[6]:
IntervalIndex([(0, 1], (1, 2], (2, 3]]
              closed='right',
              dtype='interval[int64]')

However, period_range ignores the end parameter:

In [7]: pd.period_range(start='2017Q1', end='2017Q4', periods=6, freq='Q')
Out[7]: PeriodIndex(['2017Q1', '2017Q2', '2017Q3', '2017Q4', '2018Q1', '2018Q2'], dtype='period[Q-DEC]', freq='Q-DEC')

Both date_range and timedelta_range raise:

In [8]: pd.date_range(start='2017-01-01', end='2017-01-04', periods=6)
ValueError: Must specify two of start, end, or periods

In [9]: pd.timedelta_range(start='1 day', end='4 days', periods=6)
ValueError: Must specify two of start, end, or periods

Proposal: interval_range and period_range should raise. Add the word "exactly" to the error message of all for additional clarity: "Must specify exactly two of start, end, or periods".

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.6.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 78 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.20.3
pytest: 3.1.2
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.26
numpy: 1.13.1
scipy: 0.19.1
xarray: None
IPython: 6.1.0
sphinx: 1.5.6
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.2.2
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.4.7
xlrd: 1.0.0
xlwt: 1.2.0
xlsxwriter: 0.9.6
lxml: 3.7.3
bs4: 4.6.0
html5lib: 0.999
sqlalchemy: 1.1.9
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None

@jschendel jschendel changed the title Make the behavior of *_range functions consistent Inconsistent behavior of *_range functions Sep 8, 2017

@jreback

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commented Sep 8, 2017

would agree with this in its entirety. go for it. pls make a sub-section in the whatsnew to explain the changes (doesn't have to be big)

@jschendel jschendel referenced this issue Sep 9, 2017

Merged

Make *_range functions consistent #17482

4 of 4 tasks complete

@jreback jreback added this to the 0.21.0 milestone Sep 10, 2017

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