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"""
Test extension array for storing nested data in a pandas container.
The JSONArray stores lists of dictionaries. The storage mechanism is a list,
not an ndarray.
Note
----
We currently store lists of UserDicts. Pandas has a few places
internally that specifically check for dicts, and does non-scalar things
in that case. We *want* the dictionaries to be treated as scalars, so we
hack around pandas by using UserDicts.
"""
from __future__ import annotations
from collections import (
UserDict,
abc,
)
import itertools
import numbers
import string
import sys
from typing import (
TYPE_CHECKING,
Any,
)
import numpy as np
from pandas.core.dtypes.cast import construct_1d_object_array_from_listlike
from pandas.core.dtypes.common import (
is_bool_dtype,
is_list_like,
pandas_dtype,
)
import pandas as pd
from pandas.api.extensions import (
ExtensionArray,
ExtensionDtype,
)
from pandas.core.indexers import unpack_tuple_and_ellipses
if TYPE_CHECKING:
from collections.abc import Mapping
from pandas._typing import type_t
class JSONDtype(ExtensionDtype):
type = abc.Mapping
name = "json"
na_value: Mapping[str, Any] = UserDict()
@classmethod
def construct_array_type(cls) -> type_t[JSONArray]:
"""
Return the array type associated with this dtype.
Returns
-------
type
"""
return JSONArray
class JSONArray(ExtensionArray):
dtype = JSONDtype()
__array_priority__ = 1000
def __init__(self, values, dtype=None, copy=False) -> None:
for val in values:
if not isinstance(val, self.dtype.type):
raise TypeError("All values must be of type " + str(self.dtype.type))
self.data = values
# Some aliases for common attribute names to ensure pandas supports
# these
self._items = self._data = self.data
# those aliases are currently not working due to assumptions
# in internal code (GH-20735)
# self._values = self.values = self.data
@classmethod
def _from_sequence(cls, scalars, dtype=None, copy=False):
return cls(scalars)
@classmethod
def _from_factorized(cls, values, original):
return cls([UserDict(x) for x in values if x != ()])
def __getitem__(self, item):
if isinstance(item, tuple):
item = unpack_tuple_and_ellipses(item)
if isinstance(item, numbers.Integral):
return self.data[item]
elif isinstance(item, slice) and item == slice(None):
# Make sure we get a view
return type(self)(self.data)
elif isinstance(item, slice):
# slice
return type(self)(self.data[item])
elif not is_list_like(item):
# e.g. "foo" or 2.5
# exception message copied from numpy
raise IndexError(
r"only integers, slices (`:`), ellipsis (`...`), numpy.newaxis "
r"(`None`) and integer or boolean arrays are valid indices"
)
else:
item = pd.api.indexers.check_array_indexer(self, item)
if is_bool_dtype(item.dtype):
return self._from_sequence([x for x, m in zip(self, item) if m])
# integer
return type(self)([self.data[i] for i in item])
def __setitem__(self, key, value) -> None:
if isinstance(key, numbers.Integral):
self.data[key] = value
else:
if not isinstance(value, (type(self), abc.Sequence)):
# broadcast value
value = itertools.cycle([value])
if isinstance(key, np.ndarray) and key.dtype == "bool":
# masking
for i, (k, v) in enumerate(zip(key, value)):
if k:
assert isinstance(v, self.dtype.type)
self.data[i] = v
else:
for k, v in zip(key, value):
assert isinstance(v, self.dtype.type)
self.data[k] = v
def __len__(self) -> int:
return len(self.data)
def __eq__(self, other):
return NotImplemented
def __ne__(self, other):
return NotImplemented
def __array__(self, dtype=None):
if dtype is None:
dtype = object
if dtype == object:
# on py38 builds it looks like numpy is inferring to a non-1D array
return construct_1d_object_array_from_listlike(list(self))
return np.asarray(self.data, dtype=dtype)
@property
def nbytes(self) -> int:
return sys.getsizeof(self.data)
def isna(self):
return np.array([x == self.dtype.na_value for x in self.data], dtype=bool)
def take(self, indexer, allow_fill=False, fill_value=None):
# re-implement here, since NumPy has trouble setting
# sized objects like UserDicts into scalar slots of
# an ndarary.
indexer = np.asarray(indexer)
msg = (
"Index is out of bounds or cannot do a "
"non-empty take from an empty array."
)
if allow_fill:
if fill_value is None:
fill_value = self.dtype.na_value
# bounds check
if (indexer < -1).any():
raise ValueError
try:
output = [
self.data[loc] if loc != -1 else fill_value for loc in indexer
]
except IndexError as err:
raise IndexError(msg) from err
else:
try:
output = [self.data[loc] for loc in indexer]
except IndexError as err:
raise IndexError(msg) from err
return self._from_sequence(output)
def copy(self):
return type(self)(self.data[:])
def astype(self, dtype, copy=True):
# NumPy has issues when all the dicts are the same length.
# np.array([UserDict(...), UserDict(...)]) fails,
# but np.array([{...}, {...}]) works, so cast.
from pandas.core.arrays.string_ import StringDtype
dtype = pandas_dtype(dtype)
# needed to add this check for the Series constructor
if isinstance(dtype, type(self.dtype)) and dtype == self.dtype:
if copy:
return self.copy()
return self
elif isinstance(dtype, StringDtype):
value = self.astype(str) # numpy doesn't like nested dicts
return dtype.construct_array_type()._from_sequence(value, copy=False)
return np.array([dict(x) for x in self], dtype=dtype, copy=copy)
def unique(self):
# Parent method doesn't work since np.array will try to infer
# a 2-dim object.
return type(self)([dict(x) for x in {tuple(d.items()) for d in self.data}])
@classmethod
def _concat_same_type(cls, to_concat):
data = list(itertools.chain.from_iterable(x.data for x in to_concat))
return cls(data)
def _values_for_factorize(self):
frozen = self._values_for_argsort()
if len(frozen) == 0:
# factorize_array expects 1-d array, this is a len-0 2-d array.
frozen = frozen.ravel()
return frozen, ()
def _values_for_argsort(self):
# Bypass NumPy's shape inference to get a (N,) array of tuples.
frozen = [tuple(x.items()) for x in self]
return construct_1d_object_array_from_listlike(frozen)
def make_data():
# TODO: Use a regular dict. See _NDFrameIndexer._setitem_with_indexer
rng = np.random.default_rng(2)
return [
UserDict(
[
(rng.choice(list(string.ascii_letters)), rng.integers(0, 100))
for _ in range(rng.integers(0, 10))
]
)
for _ in range(100)
]