# pandas.api.extensions.ExtensionDtype

class pandas.api.extensions.ExtensionDtype

  A custom data type, to be paired with an ExtensionArray.

  See also

  `extensions.register_extension_dtype`

    Register an ExtensionType with pandas as class decorator.

  `extensions.ExtensionArray`

    Abstract base class for custom 1-D array types.

  Notes

  The interface includes the following abstract methods that must be implemented by subclasses:

  - type

  - name

  - construct_array_type

  The following attributes and methods influence the behavior of the dtype in pandas operations

  - _is_numeric

  - _is_boolean

  - _get_common_dtype

  The na_value class attribute can be used to set the default NA value for this type. `numpy.nan` is used by default.

  ExtensionDtypes are required to be hashable. The base class provides a default implementation, which relies on the `_metadata` class attribute. `_metadata` should be a tuple containing the strings that define your data type. For example, with `PeriodDtype` that’s the `freq` attribute.

  If you have a parametrized dtype you should set the ``_metadata`` class property.

  Ideally, the attributes in `_metadata` will match the parameters to your `ExtensionDtype.__init__` (if any). If any of the attributes in `_metadata` don’t implement the standard `__eq__` or `__hash__`, the default implementations here will not work.

  For interaction with Apache Arrow (pyarrow), a `__from_arrow__` method can be implemented: this method receives a pyarrow Array or ChunkedArray as only argument and is expected to return the appropriate pandas ExtensionArray for this dtype and the passed values:

      class ExtensionDtype:

          def __from_arrow__(
              self, array: Union[pyarrow.Array, pyarrow.ChunkedArray]
          ) -> ExtensionArray:
              ...

  This class does not inherit from ‘abc.ABCMeta’ for performance reasons. Methods and properties required by the interface raise `pandas.errors.AbstractMethodError` and no `register` method is provided for registering virtual subclasses.

  Attributes

  `kind` | A character code (one of 'biufcmMOSUV'), default 'O'
  `na_value` | Default NA value to use for this type.
  `name` | A string identifying the data type.
  `names` | Ordered list of field names, or None if there are no fields.
  `type` | The scalar type for the array, e.g.

  Methods

  `construct_array_type`() | Return the array type associated with this dtype.
  `construct_from_string`(string) | Construct this type from a string.
  `is_dtype`(dtype) | Check if we match 'dtype'.