pyarrow.ChunkedArray#

class pyarrow.ChunkedArray#

Bases: pyarrow.lib._PandasConvertible

An array-like composed from a (possibly empty) collection of pyarrow.Arrays

Warning

Do not call this class’s constructor directly.

Examples

To construct a ChunkedArray object use pyarrow.chunked_array():

>>> import pyarrow as pa
>>> pa.chunked_array([], type=pa.int8())
<pyarrow.lib.ChunkedArray object at ...>
[
...
]

>>> pa.chunked_array([[2, 2, 4], [4, 5, 100]])
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> isinstance(pa.chunked_array([[2, 2, 4], [4, 5, 100]]), pa.ChunkedArray)
True

__init__(*args, **kwargs)#

Methods

`__init__`(args, *kwargs)
`cast`(self, target_type[, safe])	Cast array values to another data type
`chunk`(self, i)	Select a chunk by its index.
`combine_chunks`(self, MemoryPool memory_pool=None)	Flatten this ChunkedArray into a single non-chunked array.
`dictionary_encode`(self[, null_encoding])	Compute dictionary-encoded representation of array.
`drop_null`(self)	Remove missing values from a chunked array.
`equals`(self, ChunkedArray other)	Return whether the contents of two chunked arrays are equal.
`fill_null`(self, fill_value)	Replace each null element in values with fill_value.
`filter`(self, mask[, null_selection_behavior])	Select values from the chunked array.
`flatten`(self, MemoryPool memory_pool=None)	Flatten this ChunkedArray.
`format`(self, **kwargs)
`get_total_buffer_size`(self)	The sum of bytes in each buffer referenced by the chunked array.
`index`(self, value[, start, end, memory_pool])	Find the first index of a value.
`is_null`(self, *[, nan_is_null])	Return boolean array indicating the null values.
`is_valid`(self)	Return boolean array indicating the non-null values.
`iterchunks`(self)	Convert to an iterator of ChunkArrays.
`length`(self)	Return length of a ChunkedArray.
`slice`(self[, offset, length])	Compute zero-copy slice of this ChunkedArray
`take`(self, indices)	Select values from the chunked array.
`to_numpy`(self)	Return a NumPy copy of this array (experimental).
`to_pandas`(self[, memory_pool, categories, ...])	Convert to a pandas-compatible NumPy array or DataFrame, as appropriate
`to_pylist`(self)	Convert to a list of native Python objects.
`to_string`(self, *, int indent=0, ...)	Render a "pretty-printed" string representation of the ChunkedArray
`unify_dictionaries`(self, ...)	Unify dictionaries across all chunks.
`unique`(self)	Compute distinct elements in array
`validate`(self, *[, full])	Perform validation checks.
`value_counts`(self)	Compute counts of unique elements in array.

Attributes

`chunks`	Convert to a list of single-chunked arrays.
`data`
`nbytes`	Total number of bytes consumed by the elements of the chunked array.
`null_count`	Number of null entries
`num_chunks`	Number of underlying chunks.
`type`	Return data type of a ChunkedArray.

cast(self, target_type, safe=True)#

Cast array values to another data type

See pyarrow.compute.cast() for usage.

Parameters

target_typeDataType: Type to cast array to.
safebool, default True: Whether to check for conversion errors such as overflow.

Returns

castArray or ChunkedArray

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs.type
DataType(int64)

Change the data type of an array:

>>> n_legs_seconds = n_legs.cast(pa.duration('s'))
>>> n_legs_seconds.type
DurationType(duration[s])

chunk(self, i)#

Select a chunk by its index.

Parameters

iint

Returns

pyarrow.Array

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, None], [4, 5, 100]])
>>> n_legs.chunk(1)
<pyarrow.lib.Int64Array object at ...>
[
  4,
  5,
  100
]

chunks#

Convert to a list of single-chunked arrays.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, None], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    null
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.chunks
[<pyarrow.lib.Int64Array object at ...>
[
  2,
  2,
  null
], <pyarrow.lib.Int64Array object at ...>
[
  4,
  5,
  100
]]

combine_chunks(self, MemoryPool memory_pool=None)#

Flatten this ChunkedArray into a single non-chunked array.

Parameters

memory_poolMemoryPool, default None: For memory allocations, if required, otherwise use default pool

Returns

resultArray

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.combine_chunks()
<pyarrow.lib.Int64Array object at ...>
[
  2,
  2,
  4,
  4,
  5,
  100
]

data#

dictionary_encode(self, null_encoding='mask')#

Compute dictionary-encoded representation of array.

See pyarrow.compute.dictionary_encode() for full usage.

Parameters

null_encoding: How to handle null entries.

Returns

encodedChunkedArray: A dictionary-encoded version of this array.

Examples

>>> import pyarrow as pa
>>> animals = pa.chunked_array((
...             ["Flamingo", "Parot", "Dog"],
...             ["Horse", "Brittle stars", "Centipede"]
...             ))
>>> animals.dictionary_encode()
<pyarrow.lib.ChunkedArray object at ...>
[
...
  -- dictionary:
    [
      "Flamingo",
      "Parot",
      "Dog",
      "Horse",
      "Brittle stars",
      "Centipede"
    ]
  -- indices:
    [
      0,
      1,
      2
    ],
...
  -- dictionary:
    [
      "Flamingo",
      "Parot",
      "Dog",
      "Horse",
      "Brittle stars",
      "Centipede"
    ]
  -- indices:
    [
      3,
      4,
      5
    ]
]

drop_null(self)#

Remove missing values from a chunked array. See pyarrow.compute.drop_null() for full description.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, None], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    null
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.drop_null()
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2
  ],
  [
    4,
    5,
    100
  ]
]

equals(self, ChunkedArray other)#

Return whether the contents of two chunked arrays are equal.

Parameters

otherpyarrow.ChunkedArray: Chunked array to compare against.

Returns

are_equalbool

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> animals = pa.chunked_array((
...             ["Flamingo", "Parot", "Dog"],
...             ["Horse", "Brittle stars", "Centipede"]
...             ))
>>> n_legs.equals(n_legs)
True
>>> n_legs.equals(animals)
False

fill_null(self, fill_value)#

Replace each null element in values with fill_value.

See pyarrow.compute.fill_null() for full usage.

Parameters

fill_value: The replacement value for null entries.

Returns

resultArray or ChunkedArray: A new array with nulls replaced by the given value.

Examples

>>> import pyarrow as pa
>>> fill_value = pa.scalar(5, type=pa.int8())
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.fill_null(fill_value)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4,
    4,
    5,
    100
  ]
]

filter(self, mask, null_selection_behavior='drop')#

Select values from the chunked array.

See pyarrow.compute.filter() for full usage.

Parameters

maskArray or array-like: The boolean mask to filter the chunked array with.
null_selection_behavior: How nulls in the mask should be handled.

Returns

filteredArray or ChunkedArray: An array of the same type, with only the elements selected by the boolean mask.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> mask = pa.array([True, False, None, True, False, True])
>>> n_legs.filter(mask)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2
  ],
  [
    4,
    100
  ]
]
>>> n_legs.filter(mask, null_selection_behavior="emit_null")
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    null
  ],
  [
    4,
    100
  ]
]

flatten(self, MemoryPool memory_pool=None)#

Flatten this ChunkedArray. If it has a struct type, the column is flattened into one array per struct field.

Parameters

memory_poolMemoryPool, default None: For memory allocations, if required, otherwise use default pool

Returns

resultlist of ChunkedArray

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> c_arr = pa.chunked_array(n_legs.value_counts())
>>> c_arr
<pyarrow.lib.ChunkedArray object at ...>
[
  -- is_valid: all not null
  -- child 0 type: int64
    [
      2,
      4,
      5,
      100
    ]
  -- child 1 type: int64
    [
      2,
      2,
      1,
      1
    ]
]
>>> c_arr.flatten()
[<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    4,
    5,
    100
  ]
], <pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    1,
    1
  ]
]]
>>> c_arr.type
StructType(struct<values: int64, counts: int64>)
>>> n_legs.type
DataType(int64)

format(self, **kwargs)#

get_total_buffer_size(self)#

The sum of bytes in each buffer referenced by the chunked array.

An array may only reference a portion of a buffer. This method will overestimate in this case and return the byte size of the entire buffer.

If a buffer is referenced multiple times then it will only be counted once.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.get_total_buffer_size()
49

index(self, value, start=None, end=None, *, memory_pool=None)#

Find the first index of a value.

See pyarrow.compute.index() for full usage.

Parameters

valueScalar or object: The value to look for in the array.
startint, optional: The start index where to look for value.
endint, optional: The end index where to look for value.
memory_poolMemoryPool, optional: A memory pool for potential memory allocations.

Returns

indexInt64Scalar: The index of the value in the array (-1 if not found).

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.index(4)
<pyarrow.Int64Scalar: 2>
>>> n_legs.index(4, start=3)
<pyarrow.Int64Scalar: 3>

is_null(self, *, nan_is_null=False)#

Return boolean array indicating the null values.

Parameters

nan_is_nullbool (optional, default False): Whether floating-point NaN values should also be considered null.

Returns

arraybool Array or ChunkedArray

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.is_null()
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    false,
    false,
    false
  ],
  [
    false,
    true,
    false
  ]
]

is_valid(self)#

Return boolean array indicating the non-null values.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.is_valid()
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    true,
    true,
    true
  ],
  [
    true,
    false,
    true
  ]
]

iterchunks(self)#

Convert to an iterator of ChunkArrays.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> for i in n_legs.iterchunks():
...     print(i.null_count)
...
0
1

length(self)#

Return length of a ChunkedArray.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs.length()
6

nbytes#

Total number of bytes consumed by the elements of the chunked array.

In other words, the sum of bytes from all buffer ranges referenced.

Unlike get_total_buffer_size this method will account for array offsets.

If buffers are shared between arrays then the shared portion will only be counted multiple times.

The dictionary of dictionary arrays will always be counted in their entirety even if the array only references a portion of the dictionary.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.nbytes
49

null_count#

Number of null entries

Returns

int

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.null_count
1

num_chunks#

Number of underlying chunks.

Returns

int

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, None], [4, 5, 100]])
>>> n_legs.num_chunks
2

slice(self, offset=0, length=None)#

Compute zero-copy slice of this ChunkedArray

Parameters

offsetint, default 0: Offset from start of array to slice
lengthint, default None: Length of slice (default is until end of batch starting from offset)

Returns

slicedChunkedArray

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.slice(2,2)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    4
  ],
  [
    4
  ]
]

take(self, indices)#

Select values from the chunked array.

See pyarrow.compute.take() for full usage.

Parameters

indicesArray or array-like: The indices in the array whose values will be returned.

Returns

takenArray or ChunkedArray: An array with the same datatype, containing the taken values.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.take([1,4,5])
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    5,
    100
  ]
]

to_numpy(self)#

Return a NumPy copy of this array (experimental).

Returns

arraynumpy.ndarray

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs.to_numpy()
array([  2,   2,   4,   4,   5, 100])

to_pandas(self, memory_pool=None, categories=None, bool strings_to_categorical=False, bool zero_copy_only=False, bool integer_object_nulls=False, bool date_as_object=True, bool timestamp_as_object=False, bool use_threads=True, bool deduplicate_objects=True, bool ignore_metadata=False, bool safe=True, bool split_blocks=False, bool self_destruct=False, types_mapper=None)#

Convert to a pandas-compatible NumPy array or DataFrame, as appropriate

Parameters

memory_poolMemoryPool, default None

Arrow MemoryPool to use for allocations. Uses the default memory pool is not passed.

strings_to_categoricalbool, default False

Encode string (UTF8) and binary types to pandas.Categorical.

categorieslist, default empty

List of fields that should be returned as pandas.Categorical. Only applies to table-like data structures.

zero_copy_onlybool, default False

Raise an ArrowException if this function call would require copying the underlying data.

integer_object_nullsbool, default False

Cast integers with nulls to objects

date_as_objectbool, default True

Cast dates to objects. If False, convert to datetime64[ns] dtype.

timestamp_as_objectbool, default False

Cast non-nanosecond timestamps (np.datetime64) to objects. This is useful if you have timestamps that don’t fit in the normal date range of nanosecond timestamps (1678 CE-2262 CE). If False, all timestamps are converted to datetime64[ns] dtype.

use_threadsbool, default True

Whether to parallelize the conversion using multiple threads.

deduplicate_objectsbool, default False

Do not create multiple copies Python objects when created, to save on memory use. Conversion will be slower.

ignore_metadatabool, default False

If True, do not use the ‘pandas’ metadata to reconstruct the DataFrame index, if present

safebool, default True

For certain data types, a cast is needed in order to store the data in a pandas DataFrame or Series (e.g. timestamps are always stored as nanoseconds in pandas). This option controls whether it is a safe cast or not.

split_blocksbool, default False

If True, generate one internal “block” for each column when creating a pandas.DataFrame from a RecordBatch or Table. While this can temporarily reduce memory note that various pandas operations can trigger “consolidation” which may balloon memory use.

self_destructbool, default False

EXPERIMENTAL: If True, attempt to deallocate the originating Arrow memory while converting the Arrow object to pandas. If you use the object after calling to_pandas with this option it will crash your program.

Note that you may not see always memory usage improvements. For example, if multiple columns share an underlying allocation, memory can’t be freed until all columns are converted.

types_mapperfunction, default None

A function mapping a pyarrow DataType to a pandas ExtensionDtype. This can be used to override the default pandas type for conversion of built-in pyarrow types or in absence of pandas_metadata in the Table schema. The function receives a pyarrow DataType and is expected to return a pandas ExtensionDtype or None if the default conversion should be used for that type. If you have a dictionary mapping, you can pass dict.get as function.

Returns

pandas.Series or pandas.DataFrame depending on type of object

Examples

>>> import pyarrow as pa
>>> import pandas as pd

Convert a Table to pandas DataFrame:

>>> table = pa.table([
...    pa.array([2, 4, 5, 100]),
...    pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"])
...    ], names=['n_legs', 'animals'])
>>> table.to_pandas()
   n_legs        animals
0       2       Flamingo
1       4          Horse
2       5  Brittle stars
3     100      Centipede
>>> isinstance(table.to_pandas(), pd.DataFrame)
True

Convert a RecordBatch to pandas DataFrame:

>>> import pyarrow as pa
>>> n_legs = pa.array([2, 4, 5, 100])
>>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"])
>>> batch = pa.record_batch([n_legs, animals],
...                         names=["n_legs", "animals"])
>>> batch
pyarrow.RecordBatch
n_legs: int64
animals: string
>>> batch.to_pandas()
   n_legs        animals
0       2       Flamingo
1       4          Horse
2       5  Brittle stars
3     100      Centipede
>>> isinstance(batch.to_pandas(), pd.DataFrame)
True

Convert a Chunked Array to pandas Series:

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs.to_pandas()
0      2
1      2
2      4
3      4
4      5
5    100
dtype: int64
>>> isinstance(n_legs.to_pandas(), pd.Series)
True

to_pylist(self)#

Convert to a list of native Python objects.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, None, 100]])
>>> n_legs.to_pylist()
[2, 2, 4, 4, None, 100]

to_string(self, *, int indent=0, int window=5, int container_window=2, bool skip_new_lines=False)#

Render a “pretty-printed” string representation of the ChunkedArray

Parameters

indentint: How much to indent right the content of the array, by default 0.
windowint: How many items to preview within each chunk at the begin and end of the chunk when the chunk is bigger than the window. The other elements will be ellipsed.
container_windowint: How many chunks to preview at the begin and end of the array when the array is bigger than the window. The other elements will be ellipsed. This setting also applies to list columns.
skip_new_linesbool: If the array should be rendered as a single line of text or if each element should be on its own line.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs.to_string(skip_new_lines=True)
'[[2,2,4],[4,5,100]]'

type#

Return data type of a ChunkedArray.

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs.type
DataType(int64)

unify_dictionaries(self, MemoryPool memory_pool=None)#

Unify dictionaries across all chunks.

This method returns an equivalent chunked array, but where all chunks share the same dictionary values. Dictionary indices are transposed accordingly.

If there are no dictionaries in the chunked array, it is returned unchanged.

Parameters

memory_poolMemoryPool, default None: For memory allocations, if required, otherwise use default pool

Returns

resultChunkedArray

Examples

>>> import pyarrow as pa
>>> arr_1 = pa.array(["Flamingo", "Parot", "Dog"]).dictionary_encode()
>>> arr_2 = pa.array(["Horse", "Brittle stars", "Centipede"]).dictionary_encode()
>>> c_arr = pa.chunked_array([arr_1, arr_2])
>>> c_arr
<pyarrow.lib.ChunkedArray object at ...>
[
...
  -- dictionary:
    [
      "Flamingo",
      "Parot",
      "Dog"
    ]
  -- indices:
    [
      0,
      1,
      2
    ],
...
  -- dictionary:
    [
      "Horse",
      "Brittle stars",
      "Centipede"
    ]
  -- indices:
    [
      0,
      1,
      2
    ]
]
>>> c_arr.unify_dictionaries()
<pyarrow.lib.ChunkedArray object at ...>
[
...
  -- dictionary:
    [
      "Flamingo",
      "Parot",
      "Dog",
      "Horse",
      "Brittle stars",
      "Centipede"
    ]
  -- indices:
    [
      0,
      1,
      2
    ],
...
  -- dictionary:
    [
      "Flamingo",
      "Parot",
      "Dog",
      "Horse",
      "Brittle stars",
      "Centipede"
    ]
  -- indices:
    [
      3,
      4,
      5
    ]
]

unique(self)#

Compute distinct elements in array

Returns

pyarrow.Array

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.unique()
<pyarrow.lib.Int64Array object at ...>
[
  2,
  4,
  5,
  100
]

validate(self, *, full=False)#

Perform validation checks. An exception is raised if validation fails.

By default only cheap validation checks are run. Pass full=True for thorough validation checks (potentially O(n)).

Parameters

fullbool, default False: If True, run expensive checks, otherwise cheap checks only.

Raises

ArrowInvalid

value_counts(self)#

Compute counts of unique elements in array.

Returns

An array of <input type “Values”, int64_t “Counts”> structs

Examples

>>> import pyarrow as pa
>>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]])
>>> n_legs
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    2,
    4
  ],
  [
    4,
    5,
    100
  ]
]
>>> n_legs.value_counts()
<pyarrow.lib.StructArray object at ...>
-- is_valid: all not null
-- child 0 type: int64
  [
    2,
    4,
    5,
    100
  ]
-- child 1 type: int64
  [
    2,
    2,
    1,
    1
  ]

pyarrow.table

pyarrow.RecordBatch