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DEPR: Series.first() and DataFrame.first() #53419

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Merged
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Jun 1, 2023
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DEPR: Series.first() and DataFrame.first() #53419

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8de4ffa
Deprecating first()
DeaMariaLeon May 27, 2023
96ce115
Added requested changes
DeaMariaLeon May 29, 2023
ac7707a
Merge remote-tracking branch 'upstream/main' into deprfirst
DeaMariaLeon May 29, 2023
75ee3b1
removed repeated ts
DeaMariaLeon May 29, 2023
6cd46c8
Update doc/source/whatsnew/v2.1.0.rst
MarcoGorelli May 29, 2023
b8e30b4
Update pandas/core/generic.py
MarcoGorelli May 29, 2023
51e75fe
pre-commit
MarcoGorelli May 29, 2023
8fe71ff
Separated test for first() on test_finalize.py
DeaMariaLeon May 30, 2023
e195758
Avoiding docstring on CI
DeaMariaLeon May 30, 2023
148ddfd
Merge remote-tracking branch 'upstream/main' into deprfirst
DeaMariaLeon May 30, 2023
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6 changes: 6 additions & 0 deletions pandas/core/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9162,6 +9162,12 @@ def first(self, offset) -> Self:
3 days observed in the dataset, and therefore data for 2018-04-13 was
not returned.
"""
# GH45908 & GH#52487
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I don't think we need the issue numbers here

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Thanks

warnings.warn(
"first is deprecated and will be removed in a future version",
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shall we advise users what to do instead? something like "please create a mask and filter using .loc instead"

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Yes

FutureWarning,
stacklevel=find_stack_level(),
)
if not isinstance(self.index, DatetimeIndex):
raise TypeError("'first' only supports a DatetimeIndex index")

Expand Down
70 changes: 40 additions & 30 deletions pandas/tests/frame/methods/test_first_and_last.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,38 +10,43 @@
)
import pandas._testing as tm

deprecated_msg = "first is deprecated"


class TestFirst:
def test_first_subset(self, frame_or_series):
ts = tm.makeTimeDataFrame(freq="12h")
ts = tm.get_obj(ts, frame_or_series)
result = ts.first("10d")
assert len(result) == 20
with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
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could we perhaps just do something like

        ts = tm.makeTimeDataFrame(freq="12h")
        ts = tm.get_obj(ts, frame_or_series)
        with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
            result = ts.first("10d")

        ts = tm.makeTimeDataFrame(freq="D")
        ts = tm.get_obj(ts, frame_or_series)
        with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
            result = ts.first("10d")

so that within each assert_produces_warning, there is just a single statement?

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Sure 🫣

result = ts.first("10d")

ts = tm.makeTimeDataFrame(freq="D")
ts = tm.get_obj(ts, frame_or_series)
result = ts.first("10d")
assert len(result) == 10
assert len(result) == 20

result = ts.first("3M")
expected = ts[:"3/31/2000"]
tm.assert_equal(result, expected)
ts = tm.makeTimeDataFrame(freq="D")
ts = tm.get_obj(ts, frame_or_series)
result = ts.first("10d")
assert len(result) == 10

result = ts.first("21D")
expected = ts[:21]
tm.assert_equal(result, expected)
result = ts.first("3M")
expected = ts[:"3/31/2000"]
tm.assert_equal(result, expected)

result = ts[:0].first("3M")
tm.assert_equal(result, ts[:0])
result = ts.first("21D")
expected = ts[:21]
tm.assert_equal(result, expected)

result = ts[:0].first("3M")
tm.assert_equal(result, ts[:0])

def test_first_last_raises(self, frame_or_series):
# GH#20725
obj = DataFrame([[1, 2, 3], [4, 5, 6]])
obj = tm.get_obj(obj, frame_or_series)

msg = "'first' only supports a DatetimeIndex index"
with pytest.raises(TypeError, match=msg): # index is not a DatetimeIndex
obj.first("1D")
with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
with pytest.raises(TypeError, match=msg): # index is not a DatetimeIndex
obj.first("1D")
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this is fine, though an alternative would be

with (
    tm.assert_produces_warning(FutureWarning, match=deprecated_msg),
    pytest.raises(TypeError, match=msg)
):
    obj.first('1D')

There's a ruff check for this https://beta.ruff.rs/docs/rules/multiple-with-statements/ , in case you wanted to make a separate issue about it and we can enable it globally in a separate PR

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I opened a new issue.

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Imo this looks very ugly as soon as one of both statements gets longer. I would prefer keeping them separate for tests at least

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@phofl Separate like this you mean?:

with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
            with pytest.raises(TypeError, match=msg):  # index is not a DatetimeIndex
                obj.first("1D")


msg = "'last' only supports a DatetimeIndex index"
with pytest.raises(TypeError, match=msg): # index is not a DatetimeIndex
Expand Down Expand Up @@ -73,25 +78,30 @@ def test_last_subset(self, frame_or_series):
def test_first_with_first_day_last_of_month(self, frame_or_series, start, periods):
# GH#29623
x = frame_or_series([1] * 100, index=bdate_range(start, periods=100))
result = x.first("1M")
expected = frame_or_series(
[1] * periods, index=bdate_range(start, periods=periods)
)
tm.assert_equal(result, expected)
with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
result = x.first("1M")
expected = frame_or_series(
[1] * periods, index=bdate_range(start, periods=periods)
)
tm.assert_equal(result, expected)
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let's take this out of the with context


def test_first_with_first_day_end_of_frq_n_greater_one(self, frame_or_series):
# GH#29623
x = frame_or_series([1] * 100, index=bdate_range("2010-03-31", periods=100))
result = x.first("2M")
expected = frame_or_series(
[1] * 23, index=bdate_range("2010-03-31", "2010-04-30")
)
tm.assert_equal(result, expected)

@pytest.mark.parametrize("func", ["first", "last"])
def test_empty_not_input(self, func):
with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
result = x.first("2M")
expected = frame_or_series(
[1] * 23, index=bdate_range("2010-03-31", "2010-04-30")
)
tm.assert_equal(result, expected)

def test_empty_not_input(self):
# GH#51032
df = DataFrame(index=pd.DatetimeIndex([]))
result = getattr(df, func)(offset=1)
result = getattr(df, "last")(offset=1)
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if we're doing getattr with a literal, we may as well just write df.last

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Yes, thanks


with tm.assert_produces_warning(FutureWarning, match=deprecated_msg):
result = getattr(df, "first")(offset=1)

tm.assert_frame_equal(df, result)
assert df is not result