# pandas.api.extensions.ExtensionDtype

class `pandas.api.extensions.``ExtensionDtype`

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

  New in version 0.23.0.

  See also

  `extensions.register_extension_dtype`, `extensions.ExtensionArray`

  Notes

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

  - type
  - name
  - construct_from_string

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

  - _is_numeric
  - _is_boolean

  Optionally one can override construct_array_type for construction with the name of this dtype via the Registry. See `extensions.register_extension_dtype()`.

  - construct_array_type

  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.

  Changed in version 0.24.0: Added `_metadata`, `__hash__`, and changed the default definition of `__eq__`.

  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’.

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