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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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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v0.23.1.txt
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Expand Up @@ -92,7 +92,7 @@ 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 IO JSON methods reading empty JSON schema back to DataFrame caused an error (:issue:`21287`)
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Explicitly reference :func:`read_json` and make sure to qualify that this only applies when ``orient='table'``

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Can also update reference to :class:`DataFrame`


Plotting
^^^^^^^^
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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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11 changes: 11 additions & 0 deletions pandas/tests/io/json/test_json_table_schema.py
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Expand Up @@ -12,6 +12,7 @@
from pandas.io.json.table_schema import (
as_json_table_type,
build_table_schema,
parse_table_schema,
convert_pandas_type_to_json_field,
convert_json_field_to_pandas_type,
set_default_names)
Expand Down Expand Up @@ -86,6 +87,16 @@ def test_multiindex(self):
assert result == expected


class TestParseSchema(object):
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Shouldn't need a new class here - can you just move this to TestTableOrientReader?


def test_empty_json_data(self):
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Rename this to test_empty_frame_roundtrip

# GH21287
df = pd.DataFrame([], columns=['a', 'b', 'c'])
json = df.to_json(None, orient='table')
df = parse_table_schema(json, True)
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Let's use pd.read_json here instead

assert df.empty
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To make sure that we've preserved the frame metadata we should use the tm.assert_frame_equal function here. Typically with tests we will:

  1. Create a variable called expected, which is very explicit about what we want (here that's just a copy of df)
  2. Assign to a variable called result, which here would be the result of pd.read_json
  3. Make sure result and expected match using tm.assert_frame_equal



class TestTableSchemaType(object):

@pytest.mark.parametrize('int_type', [
Expand Down