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BUG: Fix empty Data frames to JSON round-trippable back to data frames #21318

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Merged
merged 15 commits into from
Jun 8, 2018
Merged

BUG: Fix empty Data frames to JSON round-trippable back to data frames #21318

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6dfd976
BUG: Fix empty Data frames to JSON round-trippable back to data frame…
Jun 4, 2018
466e5a6
Add test and whatsnew
Jun 4, 2018
db3a738
Empty line between test classes
Jun 4, 2018
5844301
Changes based on review comments
Jun 5, 2018
fd8fa93
Fix whatsnew + PEP
Jun 5, 2018
2f347c0
Prevent empty data from being coerced to float64
Jun 5, 2018
28d6e05
Remove debugging messages
Jun 5, 2018
743c08f
Remove obsolete imports from tests
Jun 5, 2018
833afea
Merge remote-tracking branch 'upstream/master' into empty-json-empty-…
Jun 6, 2018
2461b90
Loosen test type checks, remove length check from JSON parser
Jun 6, 2018
03a2b8a
Add GH issue number to TODO comment
Jun 6, 2018
fc15ba0
Parametrize JSON roundtrip test with xfail mark
Jun 7, 2018
0a26bf8
Merge remote-tracking branch 'upstream/master' into empty-json-empty-…
Jun 8, 2018
ecc631a
Merge branch 'master' into PR_TOOL_MERGE_PR_21318
jreback Jun 8, 2018
8d5f127
fix whatsnew
jreback Jun 8, 2018
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3 changes: 2 additions & 1 deletion doc/source/whatsnew/v0.23.1.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,7 @@ I/O
- Bug in IO methods specifying ``compression='zip'`` which produced uncompressed zip archives (:issue:`17778`, :issue:`21144`)
- Bug in :meth:`DataFrame.to_stata` which prevented exporting DataFrames to buffers and most file-like objects (:issue:`21041`)
- Bug in :meth:`read_stata` and :class:`StataReader` which did not correctly decode utf-8 strings on Python 3 from Stata 14 files (dta version 118) (:issue:`21244`)
- Bug in IO JSON :func:`read_json` reading empty JSON schema with ``orient='table'`` back to :class:`DataFrame` caused an error (:issue:`21287`)

Reshaping

Expand All @@ -84,4 +85,4 @@ Reshaping

Other

- Tab completion on :class:`Index` in IPython no longer outputs deprecation warnings (:issue:`21125`)
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Why is this showing up in the diff?

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Yeah, just noticed the same. Should not be there, sry

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No worries! Merging branches can surprise you sometimes 😄

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there was a removed newline, fixed

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@pyryjook pyryjook Jun 10, 2018 •
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Great, thanks! I did not have chance to fix it during the weekend, but great that it was resolved already.

- Tab completion on :class:`Index` in IPython no longer outputs deprecation warnings (:issue:`21125`)
2 changes: 1 addition & 1 deletion pandas/io/json/table_schema.py
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Expand Up @@ -296,7 +296,7 @@ def parse_table_schema(json, precise_float):
"""
table = loads(json, precise_float=precise_float)
col_order = [field['name'] for field in table['schema']['fields']]
df = DataFrame(table['data'])[col_order]
df = DataFrame(table['data'], columns=col_order)[col_order]

dtypes = {field['name']: convert_json_field_to_pandas_type(field)
for field in table['schema']['fields']}
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13 changes: 13 additions & 0 deletions pandas/tests/io/json/test_json_table_schema.py
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Expand Up @@ -560,3 +560,16 @@ def test_multiindex(self, index_names):
out = df.to_json(orient="table")
result = pd.read_json(out, orient="table")
tm.assert_frame_equal(df, result)

@pytest.mark.parametrize("strict_check", [
pytest.param(True, marks=pytest.mark.xfail), False])
def test_empty_frame_roundtrip(self, strict_check):
# GH 21287
df = pd.DataFrame([], columns=['a', 'b', 'c'])
expected = df.copy()
out = df.to_json(orient='table')
result = pd.read_json(out, orient='table')
# TODO: When DF coercion issue (#21345) is resolved tighten type checks
tm.assert_frame_equal(expected, result,
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Minor nit but can you parametrize this with a "strict_check" parameter whose values can be True and False, with the former being marked as an xfail? You can see an example of this below:

pandas/pandas/tests/io/json/test_json_table_schema.py

Line 498 in 0c65c57

None, "idx", pytest.param("index", marks=pytest.mark.xfail),

The explicit xfail gives more visibility to the issue (I'm being overly cautious here)

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Sure, I’ll make the change. Have to say that I appreciate your pedantics on these! 😊

check_dtype=strict_check,
check_index_type=strict_check)