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BUG: closes #44312: fixes unwanted TypeError with nullable nested metadata in json_normalize #44325

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Merged
merged 1 commit into from
Nov 14, 2021
Merged

BUG: closes #44312: fixes unwanted TypeError with nullable nested metadata in json_normalize #44325

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.4.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -569,6 +569,7 @@ I/O
- Bug in :func:`read_csv`, changed exception class when expecting a file path name or file-like object from ``OSError`` to ``TypeError`` (:issue:`43366`)
- Bug in :func:`read_json` not handling non-numpy dtypes correctly (especially ``category``) (:issue:`21892`, :issue:`33205`)
- Bug in :func:`json_normalize` where multi-character ``sep`` parameter is incorrectly prefixed to every key (:issue:`43831`)
- Bug in :func:`json_normalize` where reading data with missing multi-level metadata would not respect errors="ignore" (:issue:`44312`)
- Bug in :func:`read_csv` with :code:`float_precision="round_trip"` which did not skip initial/trailing whitespace (:issue:`43713`)
- Bug in dumping/loading a :class:`DataFrame` with ``yaml.dump(frame)`` (:issue:`42748`)
-
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2 changes: 2 additions & 0 deletions pandas/io/json/_normalize.py
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Expand Up @@ -389,6 +389,8 @@ def _pull_field(
try:
if isinstance(spec, list):
for field in spec:
if result is None:
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While this fixes the issue, the typing suggests result should be dict[str, Any] from js. Is the typing incorrect or the issue more upstream?

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@qdbp qdbp Nov 8, 2021 •
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It's the Any value type on the js dict: once we're one level down we're no longer guaranteed that result is a Dict. It could be (and in this case is) None.

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Proper json typing requires recursive types, which seem to be, as of very recently, tentatively supported: python/mypy#731 (comment). This is a whole other kettle of fish, though, that will no doubt reveal a plethora of similar soundness issues.

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Got it. Could you add an informative message in KeyError and test it if possible?

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done

raise KeyError(field)
result = result[field]
else:
result = result[spec]
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27 changes: 27 additions & 0 deletions pandas/tests/io/json/test_normalize.py
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Expand Up @@ -634,6 +634,33 @@ def test_missing_meta(self, missing_metadata):
expected = DataFrame(ex_data, columns=columns)
tm.assert_frame_equal(result, expected)

def test_missing_nested_meta(self):
# GH44312
# If errors="ignore" and nested metadata is null, we should return nan
data = {"meta": "foo", "nested_meta": None, "value": [{"rec": 1}, {"rec": 2}]}
result = json_normalize(
data,
record_path="value",
meta=["meta", ["nested_meta", "leaf"]],
errors="ignore",
)
ex_data = [[1, "foo", np.nan], [2, "foo", np.nan]]
columns = ["rec", "meta", "nested_meta.leaf"]
expected = DataFrame(ex_data, columns=columns).astype(
{"nested_meta.leaf": object}
)
tm.assert_frame_equal(result, expected)

# If errors="raise" and nested metadata is null, we should raise with the
# key of the first missing level
with pytest.raises(KeyError, match="'leaf' not found"):
json_normalize(
data,
record_path="value",
meta=["meta", ["nested_meta", "leaf"]],
errors="raise",
)

def test_missing_meta_multilevel_record_path_errors_raise(self, missing_metadata):
# GH41876
# Ensure errors='raise' works as intended even when a record_path of length
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