pyarrow.Field#

class pyarrow.Field#

Bases: _Weakrefable

A named field, with a data type, nullability, and optional metadata.

Notes

Do not use this class’s constructor directly; use pyarrow.field

Examples

Create an instance of pyarrow.Field:

>>> import pyarrow as pa
>>> pa.field('key', pa.int32())
pyarrow.Field<key: int32>
>>> pa.field('key', pa.int32(), nullable=False)
pyarrow.Field<key: int32 not null>
>>> field = pa.field('key', pa.int32(),
...                  metadata={"key": "Something important"})
>>> field
pyarrow.Field<key: int32>
>>> field.metadata
{b'key': b'Something important'}

Use the field to create a struct type:

>>> pa.struct([field])
StructType(struct<key: int32>)

__init__(*args, **kwargs)#

Methods

`__init__`(args, *kwargs)
`equals`(self, Field other, ...)	Test if this field is equal to the other
`flatten`(self)	Flatten this field.
`remove_metadata`(self)	Create new field without metadata, if any
`with_metadata`(self, metadata)	Add metadata as dict of string keys and values to Field
`with_name`(self, name)	A copy of this field with the replaced name
`with_nullable`(self, nullable)	A copy of this field with the replaced nullability
`with_type`(self, DataType new_type)	A copy of this field with the replaced type

Attributes

`metadata`	The field metadata (if any is set).
`name`	The field name.
`nullable`	The field nullability.
`type`

equals(self, Field other, bool check_metadata=False)#

Test if this field is equal to the other

Parameters:

otherpyarrow.Field
check_metadatabool, default False: Whether Field metadata equality should be checked as well.

Returns:

is_equalbool

Examples

>>> import pyarrow as pa
>>> f1 = pa.field('key', pa.int32())
>>> f2 = pa.field('key', pa.int32(), nullable=False)
>>> f1.equals(f2)
False
>>> f1.equals(f1)
True

flatten(self)#

Flatten this field. If a struct field, individual child fields will be returned with their names prefixed by the parent’s name.

Returns:

fieldsList[pyarrow.Field]

Examples

>>> import pyarrow as pa
>>> f1 = pa.field('bar', pa.float64(), nullable=False)
>>> f2 = pa.field('foo', pa.int32()).with_metadata({"key": "Something important"})
>>> ff = pa.field('ff', pa.struct([f1, f2]), nullable=False)

Flatten a struct field:

>>> ff
pyarrow.Field<ff: struct<bar: double not null, foo: int32> not null>
>>> ff.flatten()
[pyarrow.Field<ff.bar: double not null>, pyarrow.Field<ff.foo: int32>]

metadata#

The field metadata (if any is set).

Returns:

metadatadict or None

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32(),
...                  metadata={"key": "Something important"})
>>> field.metadata
{b'key': b'Something important'}

name#

The field name.

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32())
>>> field.name
'key'

nullable#

The field nullability.

Examples

>>> import pyarrow as pa
>>> f1 = pa.field('key', pa.int32())
>>> f2 = pa.field('key', pa.int32(), nullable=False)
>>> f1.nullable
True
>>> f2.nullable
False

remove_metadata(self)#

Create new field without metadata, if any

Returns:

fieldpyarrow.Field

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32(),
...                  metadata={"key": "Something important"})
>>> field.metadata
{b'key': b'Something important'}

Create new field by removing the metadata from the existing one:

>>> field_new = field.remove_metadata()
>>> field_new.metadata

type#

with_metadata(self, metadata)#

Add metadata as dict of string keys and values to Field

Parameters:

metadatadict: Keys and values must be string-like / coercible to bytes

Returns:

fieldpyarrow.Field

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32())

Create new field by adding metadata to existing one:

>>> field_new = field.with_metadata({"key": "Something important"})
>>> field_new
pyarrow.Field<key: int32>
>>> field_new.metadata
{b'key': b'Something important'}

with_name(self, name)#

A copy of this field with the replaced name

Parameters:

namestr

Returns:

fieldpyarrow.Field

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32())
>>> field
pyarrow.Field<key: int32>

Create new field by replacing the name of an existing one:

>>> field_new = field.with_name('lock')
>>> field_new
pyarrow.Field<lock: int32>

with_nullable(self, nullable)#

A copy of this field with the replaced nullability

Parameters:

nullablebool

Returns:

field: pyarrow.Field

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32())
>>> field
pyarrow.Field<key: int32>
>>> field.nullable
True

Create new field by replacing the nullability of an existing one:

>>> field_new = field.with_nullable(False)
>>> field_new
pyarrow.Field<key: int32 not null>
>>> field_new.nullable
False

with_type(self, DataType new_type)#

A copy of this field with the replaced type

Parameters:

new_typepyarrow.DataType

Returns:

fieldpyarrow.Field

Examples

>>> import pyarrow as pa
>>> field = pa.field('key', pa.int32())
>>> field
pyarrow.Field<key: int32>

Create new field by replacing type of an existing one:

>>> field_new = field.with_type(pa.int64())
>>> field_new
pyarrow.Field<key: int64>