def nargsort(items, kind="quicksort", ascending=True, na_position="last"):
"""
This is intended to be a drop-in replacement for np.argsort which
handles NaNs. It adds ascending and na_position parameters.
GH #6399, #5231
"""
from pandas.core.internals.arrays import extract_array
items = extract_array(items)
mask = np.asarray(isna(items))
if is_extension_array_dtype(items):
items = items._values_for_argsort()
else:
items = np.asanyarray(items)
idx = np.arange(len(items))
non_nans = items[~mask]
non_nan_idx = idx[~mask]
nan_idx = np.nonzero(mask)[0]
if not ascending:
non_nans = non_nans[::-1]
non_nan_idx = non_nan_idx[::-1]
indexer = non_nan_idx[non_nans.argsort(kind=kind)]
if not ascending:
indexer = indexer[::-1]
# Finally, place the NaNs at the end or the beginning according to
# na_position
if na_position == "last":
indexer = np.concatenate([indexer, nan_idx])
elif na_position == "first":
indexer = np.concatenate([nan_idx, indexer])
else:
raise ValueError("invalid na_position: {!r}".format(na_position))
return indexer
def nargsort(items, kind='quicksort', ascending=True, na_position='last'):
"""
This is intended to be a drop-in replacement for np.argsort which
handles NaNs. It adds ascending and na_position parameters.
GH #6399, #5231
"""
from pandas.core.internals.arrays import extract_array
items = extract_array(items)
mask = np.asarray(isna(items))
# specially handle Categorical
if is_categorical_dtype(items):
if na_position not in {'first', 'last'}:
raise ValueError('invalid na_position: {!r}'.format(na_position))
cnt_null = mask.sum()
sorted_idx = items.argsort(ascending=ascending, kind=kind)
if ascending and na_position == 'last':
# NaN is coded as -1 and is listed in front after sorting
sorted_idx = np.roll(sorted_idx, -cnt_null)
elif not ascending and na_position == 'first':
# NaN is coded as -1 and is listed in the end after sorting
sorted_idx = np.roll(sorted_idx, cnt_null)
return sorted_idx
if is_extension_array_dtype(items):
items = items._values_for_argsort()
else:
items = np.asanyarray(items)
idx = np.arange(len(items))
non_nans = items[~mask]
non_nan_idx = idx[~mask]
nan_idx = np.nonzero(mask)[0]
if not ascending:
non_nans = non_nans[::-1]
non_nan_idx = non_nan_idx[::-1]
indexer = non_nan_idx[non_nans.argsort(kind=kind)]
if not ascending:
indexer = indexer[::-1]
# Finally, place the NaNs at the end or the beginning according to
# na_position
if na_position == 'last':
indexer = np.concatenate([indexer, nan_idx])
elif na_position == 'first':
indexer = np.concatenate([nan_idx, indexer])
else:
raise ValueError('invalid na_position: {!r}'.format(na_position))
return indexer
def _unstack_extension_series(series, level, fill_value):
"""
Unstack an ExtensionArray-backed Series.
The ExtensionDtype is preserved.
Parameters
----------
series : Series
A Series with an ExtensionArray for values
level : Any
The level name or number.
fill_value : Any
The user-level (not physical storage) fill value to use for
missing values introduced by the reshape. Passed to
``series.values.take``.
Returns
-------
DataFrame
Each column of the DataFrame will have the same dtype as
the input Series.
"""
# Implementation note: the basic idea is to
# 1. Do a regular unstack on a dummy array of integers
# 2. Followup with a columnwise take.
# We use the dummy take to discover newly-created missing values
# introduced by the reshape.
from pandas.core.reshape.concat import concat
dummy_arr = np.arange(len(series))
# fill_value=-1, since we will do a series.values.take later
result = _Unstacker(dummy_arr, series.index, level=level,
fill_value=-1).get_result()
out = []
values = extract_array(series, extract_numpy=False)
for col, indices in result.items():
out.append(
Series(
values.take(indices.values,
allow_fill=True,
fill_value=fill_value),
name=col,
index=result.index,
))
return concat(out, axis="columns", copy=False, keys=result.columns)
def _unstack_extension_series(series, level, fill_value):
"""
Unstack an ExtensionArray-backed Series.
The ExtensionDtype is preserved.
Parameters
----------
series : Series
A Series with an ExtensionArray for values
level : Any
The level name or number.
fill_value : Any
The user-level (not physical storage) fill value to use for
missing values introduced by the reshape. Passed to
``series.values.take``.
Returns
-------
DataFrame
Each column of the DataFrame will have the same dtype as
the input Series.
"""
# Implementation note: the basic idea is to
# 1. Do a regular unstack on a dummy array of integers
# 2. Followup with a columnwise take.
# We use the dummy take to discover newly-created missing values
# introduced by the reshape.
from pandas.core.reshape.concat import concat
dummy_arr = np.arange(len(series))
# fill_value=-1, since we will do a series.values.take later
result = _Unstacker(dummy_arr, series.index,
level=level, fill_value=-1).get_result()
out = []
values = extract_array(series, extract_numpy=False)
for col, indices in result.iteritems():
out.append(Series(values.take(indices.values,
allow_fill=True,
fill_value=fill_value),
name=col, index=result.index))
return concat(out, axis='columns', copy=False, keys=result.columns)
def __setitem__(self, key, value):
from pandas.core.internals.arrays import extract_array
value = extract_array(value, extract_numpy=True)
if not lib.is_scalar(key) and is_list_like(key):
key = np.asarray(key)
if not lib.is_scalar(value):
value = np.asarray(value)
values = self._ndarray
t = np.result_type(value, values)
if t != self._ndarray.dtype:
values = values.astype(t, casting='safe')
values[key] = value
self._dtype = PandasDtype(t)
self._ndarray = values
else:
self._ndarray[key] = value
def __setitem__(self, key, value):
from pandas.core.internals.arrays import extract_array
value = extract_array(value, extract_numpy=True)
if not lib.is_scalar(key) and is_list_like(key):
key = np.asarray(key)
if not lib.is_scalar(value):
value = np.asarray(value)
values = self._ndarray
t = np.result_type(value, values)
if t != self._ndarray.dtype:
values = values.astype(t, casting="safe")
values[key] = value
self._dtype = PandasDtype(t)
self._ndarray = values
else:
self._ndarray[key] = value
def sanitize_array(data,
index,
dtype=None,
copy=False,
raise_cast_failure=False):
"""
Sanitize input data to an ndarray, copy if specified, coerce to the
dtype if specified.
"""
if dtype is not None:
dtype = pandas_dtype(dtype)
if isinstance(data, ma.MaskedArray):
mask = ma.getmaskarray(data)
if mask.any():
data, fill_value = maybe_upcast(data, copy=True)
data.soften_mask() # set hardmask False if it was True
data[mask] = fill_value
else:
data = data.copy()
data = extract_array(data, extract_numpy=True)
# GH#846
if isinstance(data, np.ndarray):
if dtype is not None:
subarr = np.array(data, copy=False)
# possibility of nan -> garbage
if is_float_dtype(data.dtype) and is_integer_dtype(dtype):
try:
subarr = _try_cast(data, True, dtype, copy, True)
except ValueError:
if copy:
subarr = data.copy()
else:
subarr = _try_cast(data, True, dtype, copy, raise_cast_failure)
elif isinstance(data, Index):
# don't coerce Index types
# e.g. indexes can have different conversions (so don't fast path
# them)
# GH#6140
subarr = sanitize_index(data, index, copy=copy)
else:
# we will try to copy be-definition here
subarr = _try_cast(data, True, dtype, copy, raise_cast_failure)
elif isinstance(data, ExtensionArray):
if isinstance(data, ABCPandasArray):
# We don't want to let people put our PandasArray wrapper
# (the output of Series/Index.array), into a Series. So
# we explicitly unwrap it here.
subarr = data.to_numpy()
else:
subarr = data
# everything else in this block must also handle ndarray's,
# becuase we've unwrapped PandasArray into an ndarray.
if dtype is not None:
subarr = data.astype(dtype)
if copy:
subarr = data.copy()
return subarr
elif isinstance(data, (list, tuple)) and len(data) > 0:
if dtype is not None:
try:
subarr = _try_cast(data, False, dtype, copy,
raise_cast_failure)
except Exception:
if raise_cast_failure: # pragma: no cover
raise
subarr = np.array(data, dtype=object, copy=copy)
subarr = lib.maybe_convert_objects(subarr)
else:
subarr = maybe_convert_platform(data)
subarr = maybe_cast_to_datetime(subarr, dtype)
elif isinstance(data, range):
# GH#16804
start, stop, step = get_range_parameters(data)
arr = np.arange(start, stop, step, dtype='int64')
subarr = _try_cast(arr, False, dtype, copy, raise_cast_failure)
else:
subarr = _try_cast(data, False, dtype, copy, raise_cast_failure)
# scalar like, GH
if getattr(subarr, 'ndim', 0) == 0:
if isinstance(data, list): # pragma: no cover
subarr = np.array(data, dtype=object)
elif index is not None:
value = data
# figure out the dtype from the value (upcast if necessary)
if dtype is None:
dtype, value = infer_dtype_from_scalar(value)
else:
# need to possibly convert the value here
value = maybe_cast_to_datetime(value, dtype)
subarr = construct_1d_arraylike_from_scalar(
value, len(index), dtype)
else:
return subarr.item()
# the result that we want
elif subarr.ndim == 1:
if index is not None:
# a 1-element ndarray
if len(subarr) != len(index) and len(subarr) == 1:
subarr = construct_1d_arraylike_from_scalar(
subarr[0], len(index), subarr.dtype)
elif subarr.ndim > 1:
if isinstance(data, np.ndarray):
raise Exception('Data must be 1-dimensional')
else:
subarr = com.asarray_tuplesafe(data, dtype=dtype)
# This is to prevent mixed-type Series getting all casted to
# NumPy string type, e.g. NaN --> '-1#IND'.
if issubclass(subarr.dtype.type, compat.string_types):
# GH#16605
# If not empty convert the data to dtype
# GH#19853: If data is a scalar, subarr has already the result
if not lib.is_scalar(data):
if not np.all(isna(data)):
data = np.array(data, dtype=dtype, copy=False)
subarr = np.array(data, dtype=object, copy=copy)
if is_object_dtype(subarr.dtype) and dtype != 'object':
inferred = lib.infer_dtype(subarr, skipna=False)
if inferred == 'period':
try:
subarr = period_array(subarr)
except IncompatibleFrequency:
pass
return subarr
def array(data, # type: Sequence[object]
dtype=None, # type: Optional[Union[str, np.dtype, ExtensionDtype]]
copy=True, # type: bool
):
# type: (...) -> ExtensionArray
"""
Create an array.
.. versionadded:: 0.24.0
Parameters
----------
data : Sequence of objects
The scalars inside `data` should be instances of the
scalar type for `dtype`. It's expected that `data`
represents a 1-dimensional array of data.
When `data` is an Index or Series, the underlying array
will be extracted from `data`.
dtype : str, np.dtype, or ExtensionDtype, optional
The dtype to use for the array. This may be a NumPy
dtype or an extension type registered with pandas using
:meth:`pandas.api.extensions.register_extension_dtype`.
If not specified, there are two possibilities:
1. When `data` is a :class:`Series`, :class:`Index`, or
:class:`ExtensionArray`, the `dtype` will be taken
from the data.
2. Otherwise, pandas will attempt to infer the `dtype`
from the data.
Note that when `data` is a NumPy array, ``data.dtype`` is
*not* used for inferring the array type. This is because
NumPy cannot represent all the types of data that can be
held in extension arrays.
Currently, pandas will infer an extension dtype for sequences of
============================== =====================================
scalar type Array Type
============================= =====================================
* :class:`pandas.Interval` :class:`pandas.IntervalArray`
* :class:`pandas.Period` :class:`pandas.arrays.PeriodArray`
* :class:`datetime.datetime` :class:`pandas.arrays.DatetimeArray`
* :class:`datetime.timedelta` :class:`pandas.arrays.TimedeltaArray`
============================= =====================================
For all other cases, NumPy's usual inference rules will be used.
copy : bool, default True
Whether to copy the data, even if not necessary. Depending
on the type of `data`, creating the new array may require
copying data, even if ``copy=False``.
Returns
-------
ExtensionArray
The newly created array.
Raises
------
ValueError
When `data` is not 1-dimensional.
See Also
--------
numpy.array : Construct a NumPy array.
arrays.PandasArray : ExtensionArray wrapping a NumPy array.
Series : Construct a pandas Series.
Index : Construct a pandas Index.
Notes
-----
Omitting the `dtype` argument means pandas will attempt to infer the
best array type from the values in the data. As new array types are
added by pandas and 3rd party libraries, the "best" array type may
change. We recommend specifying `dtype` to ensure that
1. the correct array type for the data is returned
2. the returned array type doesn't change as new extension types
are added by pandas and third-party libraries
Additionally, if the underlying memory representation of the returned
array matters, we recommend specifying the `dtype` as a concrete object
rather than a string alias or allowing it to be inferred. For example,
a future version of pandas or a 3rd-party library may include a
dedicated ExtensionArray for string data. In this event, the following
would no longer return a :class:`arrays.PandasArray` backed by a NumPy
array.
>>> pd.array(['a', 'b'], dtype=str)
<PandasArray>
['a', 'b']
Length: 2, dtype: str32
This would instead return the new ExtensionArray dedicated for string
data. If you really need the new array to be backed by a NumPy array,
specify that in the dtype.
>>> pd.array(['a', 'b'], dtype=np.dtype("<U1"))
<PandasArray>
['a', 'b']
Length: 2, dtype: str32
Or use the dedicated constructor for the array you're expecting, and
wrap that in a PandasArray
>>> pd.array(np.array(['a', 'b'], dtype='<U1'))
<PandasArray>
['a', 'b']
Length: 2, dtype: str32
Examples
--------
If a dtype is not specified, `data` is passed through to
:meth:`numpy.array`, and a :class:`arrays.PandasArray` is returned.
>>> pd.array([1, 2])
<PandasArray>
[1, 2]
Length: 2, dtype: int64
Or the NumPy dtype can be specified
>>> pd.array([1, 2], dtype=np.dtype("int32"))
<PandasArray>
[1, 2]
Length: 2, dtype: int32
You can use the string alias for `dtype`
>>> pd.array(['a', 'b', 'a'], dtype='category')
[a, b, a]
Categories (2, object): [a, b]
Or specify the actual dtype
>>> pd.array(['a', 'b', 'a'],
... dtype=pd.CategoricalDtype(['a', 'b', 'c'], ordered=True))
[a, b, a]
Categories (3, object): [a < b < c]
Because omitting the `dtype` passes the data through to NumPy,
a mixture of valid integers and NA will return a floating-point
NumPy array.
>>> pd.array([1, 2, np.nan])
<PandasArray>
[1.0, 2.0, nan]
Length: 3, dtype: float64
To use pandas' nullable :class:`pandas.arrays.IntegerArray`, specify
the dtype:
>>> pd.array([1, 2, np.nan], dtype='Int64')
<IntegerArray>
[1, 2, NaN]
Length: 3, dtype: Int64
Pandas will infer an ExtensionArray for some types of data:
>>> pd.array([pd.Period('2000', freq="D"), pd.Period("2000", freq="D")])
<PeriodArray>
['2000-01-01', '2000-01-01']
Length: 2, dtype: period[D]
`data` must be 1-dimensional. A ValueError is raised when the input
has the wrong dimensionality.
>>> pd.array(1)
Traceback (most recent call last):
...
ValueError: Cannot pass scalar '1' to 'pandas.array'.
"""
from pandas.core.arrays import (
period_array, ExtensionArray, IntervalArray, PandasArray,
DatetimeArrayMixin,
TimedeltaArrayMixin,
)
from pandas.core.internals.arrays import extract_array
if lib.is_scalar(data):
msg = (
"Cannot pass scalar '{}' to 'pandas.array'."
)
raise ValueError(msg.format(data))
data = extract_array(data, extract_numpy=True)
if dtype is None and isinstance(data, ExtensionArray):
dtype = data.dtype
# this returns None for not-found dtypes.
if isinstance(dtype, compat.string_types):
dtype = registry.find(dtype) or dtype
if is_extension_array_dtype(dtype):
cls = dtype.construct_array_type()
return cls._from_sequence(data, dtype=dtype, copy=copy)
if dtype is None:
inferred_dtype = lib.infer_dtype(data)
if inferred_dtype == 'period':
try:
return period_array(data, copy=copy)
except tslibs.IncompatibleFrequency:
# We may have a mixture of frequencies.
# We choose to return an ndarray, rather than raising.
pass
elif inferred_dtype == 'interval':
try:
return IntervalArray(data, copy=copy)
except ValueError:
# We may have a mixture of `closed` here.
# We choose to return an ndarray, rather than raising.
pass
elif inferred_dtype.startswith('datetime'):
# datetime, datetime64
try:
return DatetimeArrayMixin._from_sequence(data, copy=copy)
except ValueError:
# Mixture of timezones, fall back to PandasArray
pass
elif inferred_dtype.startswith('timedelta'):
# timedelta, timedelta64
return TimedeltaArrayMixin._from_sequence(data, copy=copy)
# TODO(BooleanArray): handle this type
result = PandasArray._from_sequence(data, dtype=dtype, copy=copy)
return result
def sanitize_array(data, index, dtype=None, copy=False,
raise_cast_failure=False):
"""
Sanitize input data to an ndarray, copy if specified, coerce to the
dtype if specified.
"""
if dtype is not None:
dtype = pandas_dtype(dtype)
if isinstance(data, ma.MaskedArray):
mask = ma.getmaskarray(data)
if mask.any():
data, fill_value = maybe_upcast(data, copy=True)
data.soften_mask() # set hardmask False if it was True
data[mask] = fill_value
else:
data = data.copy()
data = extract_array(data, extract_numpy=True)
# GH#846
if isinstance(data, np.ndarray):
if dtype is not None:
subarr = np.array(data, copy=False)
# possibility of nan -> garbage
if is_float_dtype(data.dtype) and is_integer_dtype(dtype):
try:
subarr = _try_cast(data, True, dtype, copy,
True)
except ValueError:
if copy:
subarr = data.copy()
else:
subarr = _try_cast(data, True, dtype, copy, raise_cast_failure)
elif isinstance(data, Index):
# don't coerce Index types
# e.g. indexes can have different conversions (so don't fast path
# them)
# GH#6140
subarr = sanitize_index(data, index, copy=copy)
else:
# we will try to copy be-definition here
subarr = _try_cast(data, True, dtype, copy, raise_cast_failure)
elif isinstance(data, ExtensionArray):
if isinstance(data, ABCPandasArray):
# We don't want to let people put our PandasArray wrapper
# (the output of Series/Index.array), into a Series. So
# we explicitly unwrap it here.
subarr = data.to_numpy()
else:
subarr = data
# everything else in this block must also handle ndarray's,
# becuase we've unwrapped PandasArray into an ndarray.
if dtype is not None:
subarr = data.astype(dtype)
if copy:
subarr = data.copy()
return subarr
elif isinstance(data, (list, tuple)) and len(data) > 0:
if dtype is not None:
try:
subarr = _try_cast(data, False, dtype, copy,
raise_cast_failure)
except Exception:
if raise_cast_failure: # pragma: no cover
raise
subarr = np.array(data, dtype=object, copy=copy)
subarr = lib.maybe_convert_objects(subarr)
else:
subarr = maybe_convert_platform(data)
subarr = maybe_cast_to_datetime(subarr, dtype)
elif isinstance(data, range):
# GH#16804
start, stop, step = get_range_parameters(data)
arr = np.arange(start, stop, step, dtype='int64')
subarr = _try_cast(arr, False, dtype, copy, raise_cast_failure)
else:
subarr = _try_cast(data, False, dtype, copy, raise_cast_failure)
# scalar like, GH
if getattr(subarr, 'ndim', 0) == 0:
if isinstance(data, list): # pragma: no cover
subarr = np.array(data, dtype=object)
elif index is not None:
value = data
# figure out the dtype from the value (upcast if necessary)
if dtype is None:
dtype, value = infer_dtype_from_scalar(value)
else:
# need to possibly convert the value here
value = maybe_cast_to_datetime(value, dtype)
subarr = construct_1d_arraylike_from_scalar(
value, len(index), dtype)
else:
return subarr.item()
# the result that we want
elif subarr.ndim == 1:
if index is not None:
# a 1-element ndarray
if len(subarr) != len(index) and len(subarr) == 1:
subarr = construct_1d_arraylike_from_scalar(
subarr[0], len(index), subarr.dtype)
elif subarr.ndim > 1:
if isinstance(data, np.ndarray):
raise Exception('Data must be 1-dimensional')
else:
subarr = com.asarray_tuplesafe(data, dtype=dtype)
# This is to prevent mixed-type Series getting all casted to
# NumPy string type, e.g. NaN --> '-1#IND'.
if issubclass(subarr.dtype.type, compat.string_types):
# GH#16605
# If not empty convert the data to dtype
# GH#19853: If data is a scalar, subarr has already the result
if not lib.is_scalar(data):
if not np.all(isna(data)):
data = np.array(data, dtype=dtype, copy=False)
subarr = np.array(data, dtype=object, copy=copy)
if is_object_dtype(subarr.dtype) and dtype != 'object':
inferred = lib.infer_dtype(subarr, skipna=False)
if inferred == 'period':
try:
subarr = period_array(subarr)
except IncompatibleFrequency:
pass
return subarr
def sanitize_array(data,
index,
dtype=None,
copy=False,
raise_cast_failure=False):
"""
Sanitize input data to an ndarray, copy if specified, coerce to the
dtype if specified.
"""
if dtype is not None:
dtype = pandas_dtype(dtype)
if isinstance(data, ma.MaskedArray):
mask = ma.getmaskarray(data)
if mask.any():
data, fill_value = maybe_upcast(data, copy=True)
data.soften_mask() # set hardmask False if it was True
data[mask] = fill_value
else:
data = data.copy()
# extract ndarray or ExtensionArray, ensure we have no PandasArray
data = extract_array(data, extract_numpy=True)
# GH#846
if isinstance(data, np.ndarray):
if dtype is not None and is_float_dtype(
data.dtype) and is_integer_dtype(dtype):
# possibility of nan -> garbage
try:
subarr = _try_cast(data, dtype, copy, True)
except ValueError:
if copy:
subarr = data.copy()
else:
subarr = np.array(data, copy=False)
else:
# we will try to copy be-definition here
subarr = _try_cast(data, dtype, copy, raise_cast_failure)
elif isinstance(data, ExtensionArray):
# it is already ensured above this is not a PandasArray
subarr = data
if dtype is not None:
subarr = subarr.astype(dtype, copy=copy)
elif copy:
subarr = subarr.copy()
return subarr
elif isinstance(data, (list, tuple)) and len(data) > 0:
if dtype is not None:
try:
subarr = _try_cast(data, dtype, copy, raise_cast_failure)
except Exception:
if raise_cast_failure: # pragma: no cover
raise
subarr = np.array(data, dtype=object, copy=copy)
subarr = lib.maybe_convert_objects(subarr)
else:
subarr = maybe_convert_platform(data)
subarr = maybe_cast_to_datetime(subarr, dtype)
elif isinstance(data, range):
# GH#16804
arr = np.arange(data.start, data.stop, data.step, dtype="int64")
subarr = _try_cast(arr, dtype, copy, raise_cast_failure)
else:
subarr = _try_cast(data, dtype, copy, raise_cast_failure)
# scalar like, GH
if getattr(subarr, "ndim", 0) == 0:
if isinstance(data, list): # pragma: no cover
subarr = np.array(data, dtype=object)
elif index is not None:
value = data
# figure out the dtype from the value (upcast if necessary)
if dtype is None:
dtype, value = infer_dtype_from_scalar(value)
else:
# need to possibly convert the value here
value = maybe_cast_to_datetime(value, dtype)
subarr = construct_1d_arraylike_from_scalar(
value, len(index), dtype)
else:
return subarr.item()
# the result that we want
elif subarr.ndim == 1:
if index is not None:
# a 1-element ndarray
if len(subarr) != len(index) and len(subarr) == 1:
subarr = construct_1d_arraylike_from_scalar(
subarr[0], len(index), subarr.dtype)
elif subarr.ndim > 1:
if isinstance(data, np.ndarray):
raise Exception("Data must be 1-dimensional")
else:
subarr = com.asarray_tuplesafe(data, dtype=dtype)
# This is to prevent mixed-type Series getting all casted to
# NumPy string type, e.g. NaN --> '-1#IND'.
if issubclass(subarr.dtype.type, str):
# GH#16605
# If not empty convert the data to dtype
# GH#19853: If data is a scalar, subarr has already the result
if not lib.is_scalar(data):
if not np.all(isna(data)):
data = np.array(data, dtype=dtype, copy=False)
subarr = np.array(data, dtype=object, copy=copy)
if (not (is_extension_array_dtype(subarr.dtype)
or is_extension_array_dtype(dtype))
and is_object_dtype(subarr.dtype) and not is_object_dtype(dtype)):
inferred = lib.infer_dtype(subarr, skipna=False)
if inferred == "period":
try:
subarr = period_array(subarr)
except IncompatibleFrequency:
pass
return subarr
def array(data: Sequence[object],
dtype: Optional[Union[str, np.dtype, ExtensionDtype]] = None,
copy: bool = True,
) -> ABCExtensionArray:
"""
Create an array.
.. versionadded:: 0.24.0
Parameters
----------
data : Sequence of objects
The scalars inside `data` should be instances of the
scalar type for `dtype`. It's expected that `data`
represents a 1-dimensional array of data.
When `data` is an Index or Series, the underlying array
will be extracted from `data`.
dtype : str, np.dtype, or ExtensionDtype, optional
The dtype to use for the array. This may be a NumPy
dtype or an extension type registered with pandas using
:meth:`pandas.api.extensions.register_extension_dtype`.
If not specified, there are two possibilities:
1. When `data` is a :class:`Series`, :class:`Index`, or
:class:`ExtensionArray`, the `dtype` will be taken
from the data.
2. Otherwise, pandas will attempt to infer the `dtype`
from the data.
Note that when `data` is a NumPy array, ``data.dtype`` is
*not* used for inferring the array type. This is because
NumPy cannot represent all the types of data that can be
held in extension arrays.
Currently, pandas will infer an extension dtype for sequences of
============================== =====================================
Scalar Type Array Type
============================== =====================================
:class:`pandas.Interval` :class:`pandas.arrays.IntervalArray`
:class:`pandas.Period` :class:`pandas.arrays.PeriodArray`
:class:`datetime.datetime` :class:`pandas.arrays.DatetimeArray`
:class:`datetime.timedelta` :class:`pandas.arrays.TimedeltaArray`
============================== =====================================
For all other cases, NumPy's usual inference rules will be used.
copy : bool, default True
Whether to copy the data, even if not necessary. Depending
on the type of `data`, creating the new array may require
copying data, even if ``copy=False``.
Returns
-------
ExtensionArray
The newly created array.
Raises
------
ValueError
When `data` is not 1-dimensional.
See Also
--------
numpy.array : Construct a NumPy array.
Series : Construct a pandas Series.
Index : Construct a pandas Index.
arrays.PandasArray : ExtensionArray wrapping a NumPy array.
Series.array : Extract the array stored within a Series.
Notes
-----
Omitting the `dtype` argument means pandas will attempt to infer the
best array type from the values in the data. As new array types are
added by pandas and 3rd party libraries, the "best" array type may
change. We recommend specifying `dtype` to ensure that
1. the correct array type for the data is returned
2. the returned array type doesn't change as new extension types
are added by pandas and third-party libraries
Additionally, if the underlying memory representation of the returned
array matters, we recommend specifying the `dtype` as a concrete object
rather than a string alias or allowing it to be inferred. For example,
a future version of pandas or a 3rd-party library may include a
dedicated ExtensionArray for string data. In this event, the following
would no longer return a :class:`arrays.PandasArray` backed by a NumPy
array.
>>> pd.array(['a', 'b'], dtype=str)
<PandasArray>
['a', 'b']
Length: 2, dtype: str32
This would instead return the new ExtensionArray dedicated for string
data. If you really need the new array to be backed by a NumPy array,
specify that in the dtype.
>>> pd.array(['a', 'b'], dtype=np.dtype("<U1"))
<PandasArray>
['a', 'b']
Length: 2, dtype: str32
Or use the dedicated constructor for the array you're expecting, and
wrap that in a PandasArray
>>> pd.array(np.array(['a', 'b'], dtype='<U1'))
<PandasArray>
['a', 'b']
Length: 2, dtype: str32
Finally, Pandas has arrays that mostly overlap with NumPy
* :class:`arrays.DatetimeArray`
* :class:`arrays.TimedeltaArray`
When data with a ``datetime64[ns]`` or ``timedelta64[ns]`` dtype is
passed, pandas will always return a ``DatetimeArray`` or ``TimedeltaArray``
rather than a ``PandasArray``. This is for symmetry with the case of
timezone-aware data, which NumPy does not natively support.
>>> pd.array(['2015', '2016'], dtype='datetime64[ns]')
<DatetimeArray>
['2015-01-01 00:00:00', '2016-01-01 00:00:00']
Length: 2, dtype: datetime64[ns]
>>> pd.array(["1H", "2H"], dtype='timedelta64[ns]')
<TimedeltaArray>
['01:00:00', '02:00:00']
Length: 2, dtype: timedelta64[ns]
Examples
--------
If a dtype is not specified, `data` is passed through to
:meth:`numpy.array`, and a :class:`arrays.PandasArray` is returned.
>>> pd.array([1, 2])
<PandasArray>
[1, 2]
Length: 2, dtype: int64
Or the NumPy dtype can be specified
>>> pd.array([1, 2], dtype=np.dtype("int32"))
<PandasArray>
[1, 2]
Length: 2, dtype: int32
You can use the string alias for `dtype`
>>> pd.array(['a', 'b', 'a'], dtype='category')
[a, b, a]
Categories (2, object): [a, b]
Or specify the actual dtype
>>> pd.array(['a', 'b', 'a'],
... dtype=pd.CategoricalDtype(['a', 'b', 'c'], ordered=True))
[a, b, a]
Categories (3, object): [a < b < c]
Because omitting the `dtype` passes the data through to NumPy,
a mixture of valid integers and NA will return a floating-point
NumPy array.
>>> pd.array([1, 2, np.nan])
<PandasArray>
[1.0, 2.0, nan]
Length: 3, dtype: float64
To use pandas' nullable :class:`pandas.arrays.IntegerArray`, specify
the dtype:
>>> pd.array([1, 2, np.nan], dtype='Int64')
<IntegerArray>
[1, 2, NaN]
Length: 3, dtype: Int64
Pandas will infer an ExtensionArray for some types of data:
>>> pd.array([pd.Period('2000', freq="D"), pd.Period("2000", freq="D")])
<PeriodArray>
['2000-01-01', '2000-01-01']
Length: 2, dtype: period[D]
`data` must be 1-dimensional. A ValueError is raised when the input
has the wrong dimensionality.
>>> pd.array(1)
Traceback (most recent call last):
...
ValueError: Cannot pass scalar '1' to 'pandas.array'.
"""
from pandas.core.arrays import (
period_array, ExtensionArray, IntervalArray, PandasArray,
DatetimeArray,
TimedeltaArray,
)
from pandas.core.internals.arrays import extract_array
if lib.is_scalar(data):
msg = (
"Cannot pass scalar '{}' to 'pandas.array'."
)
raise ValueError(msg.format(data))
data = extract_array(data, extract_numpy=True)
if dtype is None and isinstance(data, ExtensionArray):
dtype = data.dtype
# this returns None for not-found dtypes.
if isinstance(dtype, str):
dtype = registry.find(dtype) or dtype
if is_extension_array_dtype(dtype):
cls = dtype.construct_array_type()
return cls._from_sequence(data, dtype=dtype, copy=copy)
if dtype is None:
inferred_dtype = lib.infer_dtype(data, skipna=False)
if inferred_dtype == 'period':
try:
return period_array(data, copy=copy)
except tslibs.IncompatibleFrequency:
# We may have a mixture of frequencies.
# We choose to return an ndarray, rather than raising.
pass
elif inferred_dtype == 'interval':
try:
return IntervalArray(data, copy=copy)
except ValueError:
# We may have a mixture of `closed` here.
# We choose to return an ndarray, rather than raising.
pass
elif inferred_dtype.startswith('datetime'):
# datetime, datetime64
try:
return DatetimeArray._from_sequence(data, copy=copy)
except ValueError:
# Mixture of timezones, fall back to PandasArray
pass
elif inferred_dtype.startswith('timedelta'):
# timedelta, timedelta64
return TimedeltaArray._from_sequence(data, copy=copy)
# TODO(BooleanArray): handle this type
# Pandas overrides NumPy for
# 1. datetime64[ns]
# 2. timedelta64[ns]
# so that a DatetimeArray is returned.
if is_datetime64_ns_dtype(dtype):
return DatetimeArray._from_sequence(data, dtype=dtype, copy=copy)
elif is_timedelta64_ns_dtype(dtype):
return TimedeltaArray._from_sequence(data, dtype=dtype, copy=copy)
result = PandasArray._from_sequence(data, dtype=dtype, copy=copy)
return result
