pandas.api.extensions.ExtensionArray¶

class
pandas.api.extensions.
ExtensionArray
[source]¶ Abstract base class for custom 1D array types.
pandas will recognize instances of this class as proper arrays with a custom type and will not attempt to coerce them to objects. They may be stored directly inside a
DataFrame
orSeries
.Notes
The interface includes the following abstract methods that must be implemented by subclasses:
_from_sequence
_from_factorized
__getitem__
__len__
__eq__
dtype
nbytes
isna
take
copy
_concat_same_type
A default repr displaying the type, (truncated) data, length, and dtype is provided. It can be customized or replaced by by overriding:
__repr__ : A default repr for the ExtensionArray.
_formatter : Print scalars inside a Series or DataFrame.
Some methods require casting the ExtensionArray to an ndarray of Python objects with
self.astype(object)
, which may be expensive. When performance is a concern, we highly recommend overriding the following methods:fillna
dropna
unique
factorize / _values_for_factorize
argsort / _values_for_argsort
searchsorted
The remaining methods implemented on this class should be performant, as they only compose abstract methods. Still, a more efficient implementation may be available, and these methods can be overridden.
One can implement methods to handle array reductions.
_reduce
One can implement methods to handle parsing from strings that will be used in methods such as
pandas.io.parsers.read_csv
._from_sequence_of_strings
This class does not inherit from ‘abc.ABCMeta’ for performance reasons. Methods and properties required by the interface raise
pandas.errors.AbstractMethodError
and noregister
method is provided for registering virtual subclasses.ExtensionArrays are limited to 1 dimension.
They may be backed by none, one, or many NumPy arrays. For example,
pandas.Categorical
is an extension array backed by two arrays, one for codes and one for categories. An array of IPv6 address may be backed by a NumPy structured array with two fields, one for the lower 64 bits and one for the upper 64 bits. Or they may be backed by some other storage type, like Python lists. Pandas makes no assumptions on how the data are stored, just that it can be converted to a NumPy array. The ExtensionArray interface does not impose any rules on how this data is stored. However, currently, the backing data cannot be stored in attributes called.values
or._values
to ensure full compatibility with pandas internals. But other names as.data
,._data
,._items
, … can be freely used.If implementing NumPy’s
__array_ufunc__
interface, pandas expects thatYou defer by returning
NotImplemented
when any Series are present in inputs. Pandas will extract the arrays and call the ufunc again.You define a
_HANDLED_TYPES
tuple as an attribute on the class. Pandas inspect this to determine whether the ufunc is valid for the types present.
See NumPy universal functions for more.
By default, ExtensionArrays are not hashable. Immutable subclasses may override this behavior.
Attributes
An instance of ‘ExtensionDtype’.
The number of bytes needed to store this object in memory.
Extension Arrays are only allowed to be 1dimensional.
Return a tuple of the array dimensions.
Methods
argsort
([ascending, kind, na_position])Return the indices that would sort this array.
astype
(dtype[, copy])Cast to a NumPy array with ‘dtype’.
copy
()Return a copy of the array.
dropna
()Return ExtensionArray without NA values.
factorize
([na_sentinel])Encode the extension array as an enumerated type.
fillna
([value, method, limit])Fill NA/NaN values using the specified method.
equals
(other)Return if another array is equivalent to this array.
isna
()A 1D array indicating if each value is missing.
ravel
([order])Return a flattened view on this array.
repeat
(repeats[, axis])Repeat elements of a ExtensionArray.
searchsorted
(value[, side, sorter])Find indices where elements should be inserted to maintain order.
shift
([periods, fill_value])Shift values by desired number.
take
(indices, *[, allow_fill, fill_value])Take elements from an array.
unique
()Compute the ExtensionArray of unique values.
view
([dtype])Return a view on the array.
_concat_same_type
(to_concat)Concatenate multiple array of this dtype.
_formatter
([boxed])Formatting function for scalar values.
_from_factorized
(values, original)Reconstruct an ExtensionArray after factorization.
_from_sequence
(scalars, *[, dtype, copy])Construct a new ExtensionArray from a sequence of scalars.
_from_sequence_of_strings
(strings, *[, …])Construct a new ExtensionArray from a sequence of strings.
_reduce
(name, *[, skipna])Return a scalar result of performing the reduction operation.
Return values for sorting.
Return an array and missing value suitable for factorization.