pyarrow.DictionaryType

class pyarrow.DictionaryType

Bases: DataType

Concrete class for dictionary data types.

Examples

Create an instance of dictionary type:

>>> import pyarrow as pa
>>> pa.dictionary(pa.int64(), pa.utf8())
DictionaryType(dictionary<values=string, indices=int64, ordered=0>)

__init__(*args, **kwargs)

Methods

__init__(*args, **kwargs)
equals(self, other, *[, check_metadata])	Return true if type is equivalent to passed value.
field(self, i)	Parameters:
to_pandas_dtype(self)	Return the equivalent NumPy / Pandas dtype.

Attributes

bit_width	Bit width for fixed width type.
id
index_type	The data type of dictionary indices (a signed integer type).
num_buffers	Number of data buffers required to construct Array type excluding children.
num_fields	The number of child fields.
ordered	Whether the dictionary is ordered, i.e. whether the ordering of values in the dictionary is important.
value_type	The dictionary value type.

bit_width

Bit width for fixed width type.

Examples

>>> import pyarrow as pa
>>> pa.int64()
DataType(int64)
>>> pa.int64().bit_width
64

equals(self, other, *, check_metadata=False)

Return true if type is equivalent to passed value.

Parameters:

otherDataType or str convertible to DataType

check_metadatabool

Whether nested Field metadata equality should be checked as well.

Returns:

is_equalbool

Examples

>>> import pyarrow as pa
>>> pa.int64().equals(pa.string())
False
>>> pa.int64().equals(pa.int64())
True

field(self, i) → Field

Parameters:

iint

Returns:

pyarrow.Field

id

index_type

The data type of dictionary indices (a signed integer type).

Examples

>>> import pyarrow as pa
>>> pa.dictionary(pa.int16(), pa.utf8()).index_type
DataType(int16)

num_buffers

Number of data buffers required to construct Array type excluding children.

Examples

>>> import pyarrow as pa
>>> pa.int64().num_buffers
2
>>> pa.string().num_buffers
3

num_fields

The number of child fields.

Examples

>>> import pyarrow as pa
>>> pa.int64()
DataType(int64)
>>> pa.int64().num_fields
0
>>> pa.list_(pa.string())
ListType(list<item: string>)
>>> pa.list_(pa.string()).num_fields
1
>>> struct = pa.struct({'x': pa.int32(), 'y': pa.string()})
>>> struct.num_fields
2

ordered

Whether the dictionary is ordered, i.e. whether the ordering of values in the dictionary is important.

Examples

>>> import pyarrow as pa
>>> pa.dictionary(pa.int64(), pa.utf8()).ordered
False

to_pandas_dtype(self)

Return the equivalent NumPy / Pandas dtype.

Examples

>>> import pyarrow as pa
>>> pa.int64().to_pandas_dtype()
<class 'numpy.int64'>

value_type

The dictionary value type.

The dictionary values are found in an instance of DictionaryArray.

Examples

>>> import pyarrow as pa
>>> pa.dictionary(pa.int16(), pa.utf8()).value_type
DataType(string)