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Merged
merged 13 commits into from
Feb 1, 2024
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ENH: Add check for character limmit #57103

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20e357a
Add check for character limmit
luke396 Jan 27, 2024
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luke396 Jan 27, 2024
74f4f81
Fix test
luke396 Jan 27, 2024
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Merge branch 'main' into add-character-check-to-excel-cell
luke396 Jan 27, 2024
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Fix test
luke396 Jan 27, 2024
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Fix test ingnore extra warings
luke396 Jan 28, 2024
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luke396 Jan 28, 2024
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Add what's new
luke396 Jan 28, 2024
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Merge branch 'main' into add-character-check-to-excel-cell
luke396 Jan 29, 2024
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Update doc/source/whatsnew/v3.0.0.rst
luke396 Jan 30, 2024
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Merge branch 'main' into add-character-check-to-excel-cell
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luke396 Jan 30, 2024
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v3.0.0.rst
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Expand Up @@ -28,7 +28,7 @@ enhancement2

Other enhancements
^^^^^^^^^^^^^^^^^^
-
- :func:`to_excel` now raises a ``ValueError`` when the character count in a cell exceeds Excel's limitation of 32767 characters (:issue:`56954`)
-

.. ---------------------------------------------------------------------------
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4 changes: 4 additions & 0 deletions pandas/core/generic.py
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Expand Up @@ -2363,6 +2363,10 @@ def to_excel(
Once a workbook has been saved it is not possible to write further
data without rewriting the whole workbook.

pandas will check the number of rows, columns,
and cell character count does not exceed Excel's limitations.
All other limitations must be checked by the user.

Examples
--------

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5 changes: 5 additions & 0 deletions pandas/io/excel/_base.py
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Expand Up @@ -1326,6 +1326,11 @@ def _value_with_fmt(
fmt = "0"
else:
val = str(val)
# GH#56954
if len(val) > 32767:
raise ValueError(
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Can you add a reference where 32767 comes from?

Also I think this should be a UserWarning and not a ValueError. We shouldn't completely stop writing the excel file due to excel's limitation

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@rhshadrach rhshadrach Jan 29, 2024 •
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I had suggested an error over a warning in #57103 (comment) primarily due to the fact that we raise an error if the frame is too long or wide already.

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Ah I see. The reason I suggested warning was due to a similar scenario I remember a while back where we used to raise an error if we detected whether a stack/unstack operation would create "too many elements" and users wanted to bypass that limitation. We ended up changing it to a PerformanceWarning #45084

I slightly prefer to still raise a UserWarning to make pandas less opinionated here (the Excel output is still valid and maybe a truncated value is OK for some users). But if you feel strongly about a ValueError, it's not a blocker for me

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Actually - raising here would need a deprecation too, right? That makes me think we should raise a warning. @luke396 - can you turn this back into a warning?

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Actually - raising here would need a deprecation too, right?

Conservatively yes, but it would "fix" an undesired (external) behavior ("bug").

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Truth be told, I didn't initially utilize 'UserWarning' to the extent you both recommended when I first started out. However, I gained valuable insights from the discussions you provided.

"Cell contents too long, truncated to 32767 characters"
)

return val, fmt

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9 changes: 9 additions & 0 deletions pandas/tests/io/excel/test_writers.py
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Expand Up @@ -1385,6 +1385,15 @@ def test_to_excel_empty_frame(self, engine, ext):
expected = DataFrame()
tm.assert_frame_equal(result, expected)

def test_to_excel_raising_error_when_cell_character_exceed_limit(
self, path, engine
):
# GH#56954
df = DataFrame({"A": ["a" * 32768]})
msg = "Cell contents too long, truncated to 32767 characters"
with pytest.raises(ValueError, match=msg):
df.to_excel(path, engine=engine)


class TestExcelWriterEngineTests:
@pytest.mark.parametrize(
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