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)
to_pandas_dtype(self)	Return the equivalent NumPy / Pandas dtype.

Attributes

bit_width	Bit width for fixed width type.
byte_width	Byte width for fixed width type.
has_variadic_buffers	If True, the number of expected buffers is only lower-bounded by num_buffers.
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

byte_width#

Byte width for fixed width type.

Examples

>>> import pyarrow as pa
>>> pa.int64()
DataType(int64)
>>> pa.int64().byte_width
8

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

has_variadic_buffers#

If True, the number of expected buffers is only lower-bounded by num_buffers.

Examples

>>> import pyarrow as pa
>>> pa.int64().has_variadic_buffers
False
>>> pa.string_view().has_variadic_buffers
True

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)