:mod:!array --- Efficient arrays of numeric values

.. module:: array :synopsis: Space efficient arrays of uniformly typed numeric values.

.. index:: single: arrays

This module defines an object type which can compactly represent an array of basic values: characters, integers, floating-point numbers, complex numbers. Arrays are mutable :term:sequence types and behave very much like lists, except that the type of objects stored in them is constrained. The type is specified at object creation time by using a :dfn:type code, which is a single character. The following type codes are defined:

+-----------+--------------------+-------------------+-----------------------+-------+ | Type code | C Type | Python Type | Minimum size in bytes | Notes | +===========+====================+===================+=======================+=======+ | 'b' | signed char | int | 1 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'B' | unsigned char | int | 1 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'u' | wchar_t | Unicode character | 2 | (1) | +-----------+--------------------+-------------------+-----------------------+-------+ | 'w' | Py_UCS4 | Unicode character | 4 | (2) | +-----------+--------------------+-------------------+-----------------------+-------+ | 'h' | signed short | int | 2 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'H' | unsigned short | int | 2 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'i' | signed int | int | 2 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'I' | unsigned int | int | 2 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'l' | signed long | int | 4 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'L' | unsigned long | int | 4 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'q' | signed long long | int | 8 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'Q' | unsigned long long | int | 8 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'e' | _Float16 | float | 2 | (3) | +-----------+--------------------+-------------------+-----------------------+-------+ | 'f' | float | float | 4 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'd' | double | float | 8 | | +-----------+--------------------+-------------------+-----------------------+-------+ | 'F' | float complex | complex | 8 | (4) | +-----------+--------------------+-------------------+-----------------------+-------+ | 'D' | double complex | complex | 16 | (4) | +-----------+--------------------+-------------------+-----------------------+-------+

Notes:

(1) It can be 16 bits or 32 bits depending on the platform.

.. versionchanged:: 3.9 array('u') now uses :c:type:wchar_t as C type instead of deprecated Py_UNICODE. This change doesn't affect its behavior because Py_UNICODE is alias of :c:type:wchar_t since Python 3.3.

.. deprecated-removed:: 3.3 3.16 Please migrate to 'w' typecode.

(2) .. versionadded:: 3.13

(3) The IEEE 754 binary16 "half precision" type was introduced in the 2008 revision of the IEEE 754 standard <ieee 754 standard_>_. This type is not widely supported by C compilers. It's available as :c:expr:_Float16 type, if the compiler supports the Annex H of the C23 standard.

.. versionadded:: 3.15

(4) Complex types (F and D) are available unconditionally, regardless on support for complex types (the Annex G of the C11 standard) by the C compiler. As specified in the C11 standard, each complex type is represented by a two-element C array containing, respectively, the real and imaginary parts.

.. versionadded:: 3.15

.. seealso::

The :ref:ctypes <ctypes-fundamental-data-types> and :ref:struct <format-characters> modules, as well as third-party modules like numpy <https://numpy.org/doc/stable/reference/arrays.interface.html#object.__array_interface__>__, use similar -- but slightly different -- type codes.

The actual representation of values is determined by the machine architecture (strictly speaking, by the C implementation). The actual size can be accessed through the :attr:array.itemsize attribute.

The module defines the following item:

.. data:: typecodes

A string with all available type codes.

The module defines the following type:

.. class:: array(typecode[, initializer])

A new array whose items are restricted by typecode, and initialized from the optional initializer value, which must be a :class:bytes or :class:bytearray object, a Unicode string, or iterable over elements of the appropriate type.

If given a :class:bytes or :class:bytearray object, the initializer is passed to the new array's :meth:frombytes method; if given a Unicode string, the initializer is passed to the :meth:fromunicode method; otherwise, the initializer's iterator is passed to the :meth:extend method to add initial items to the array.

Array objects support the ordinary :ref:mutable <typesseq-mutable> :term:sequence operations of indexing, slicing, concatenation, and multiplication. When using slice assignment, the assigned value must be an array object with the same type code; in all other cases, :exc:TypeError is raised. Array objects also implement the buffer interface, and may be used wherever :term:bytes-like objects <bytes-like object> are supported.

.. audit-event:: array.new typecode,initializer array.array

.. attribute:: typecode

  The typecode character used to create the array.

.. attribute:: itemsize

  The length in bytes of one array item in the internal representation.

.. method:: append(value, /)

  Append a new item with the specified value to the end of the array.

.. method:: buffer_info()

  Return a tuple ``(address, length)`` giving the current memory address and the
  length in elements of the buffer used to hold array's contents.  The size of the
  memory buffer in bytes can be computed as ``array.buffer_info()[1] *
  array.itemsize``.  This is occasionally useful when working with low-level (and
  inherently unsafe) I/O interfaces that require memory addresses, such as certain
  :c:func:`!ioctl` operations.  The returned numbers are valid as long as the array
  exists and no length-changing operations are applied to it.

  .. note::

     When using array objects from code written in C or C++ (the only way to
     effectively make use of this information), it makes more sense to use the buffer
     interface supported by array objects.  This method is maintained for backward
     compatibility and should be avoided in new code.  The buffer interface is
     documented in :ref:`bufferobjects`.

.. method:: byteswap()

  "Byteswap" all items of the array.  This is only supported for values which are
  1, 2, 4, 8 or 16 bytes in size; for other types of values, :exc:`RuntimeError` is
  raised.  It is useful when reading data from a file written on a machine with a
  different byte order.  Note, that for complex types the order of
  components (the real part, followed by imaginary part) is preserved.

.. method:: count(value, /)

  Return the number of occurrences of *value* in the array.

.. method:: extend(iterable, /)

  Append items from *iterable* to the end of the array.  If *iterable* is another
  array, it must have *exactly* the same type code; if not, :exc:`TypeError` will
  be raised.  If *iterable* is not an array, it must be iterable and its elements
  must be the right type to be appended to the array.

.. method:: frombytes(buffer, /)

  Appends items from the :term:`bytes-like object`, interpreting
  its content as an array of machine values (as if it had been read
  from a file using the :meth:`fromfile` method).

  .. versionadded:: 3.2
     :meth:`!fromstring` is renamed to :meth:`frombytes` for clarity.

.. method:: fromfile(f, n, /)

  Read *n* items (as machine values) from the :term:`file object` *f* and append
  them to the end of the array.  If less than *n* items are available,
  :exc:`EOFError` is raised, but the items that were available are still
  inserted into the array.

.. method:: fromlist(list, /)

  Append items from the list.  This is equivalent to ``for x in list:
  a.append(x)`` except that if there is a type error, the array is unchanged.

.. method:: fromunicode(ustr, /)

  Extends this array with data from the given Unicode string.
  The array must have type code ``'u'`` or ``'w'``; otherwise a :exc:`ValueError` is raised.
  Use ``array.frombytes(unicodestring.encode(enc))`` to append Unicode data to an
  array of some other type.

.. method:: index(value[, start[, stop]])

  Return the smallest *i* such that *i* is the index of the first occurrence of
  *value* in the array.  The optional arguments *start* and *stop* can be
  specified to search for *value* within a subsection of the array.  Raise
  :exc:`ValueError` if *value* is not found.

  .. versionchanged:: 3.10
     Added optional *start* and *stop* parameters.

.. method:: insert(index, value, /)

  Insert a new item *value* in the array before position *index*. Negative
  values are treated as being relative to the end of the array.

.. method:: pop(index=-1, /)

  Removes the item with the index *i* from the array and returns it. The optional
  argument defaults to ``-1``, so that by default the last item is removed and
  returned.

.. method:: remove(value, /)

  Remove the first occurrence of *value* from the array.

.. method:: clear()

  Remove all elements from the array.

  .. versionadded:: 3.13

.. method:: reverse()

  Reverse the order of the items in the array.

.. method:: tobytes()

  Convert the array to an array of machine values and return the bytes
  representation (the same sequence of bytes that would be written to a file by
  the :meth:`tofile` method.)

  .. versionadded:: 3.2
     :meth:`!tostring` is renamed to :meth:`tobytes` for clarity.

.. method:: tofile(f, /)

  Write all items (as machine values) to the :term:`file object` *f*.

.. method:: tolist()

  Convert the array to an ordinary list with the same items.

.. method:: tounicode()

  Convert the array to a Unicode string.  The array must have a type ``'u'`` or ``'w'``;
  otherwise a :exc:`ValueError` is raised. Use ``array.tobytes().decode(enc)`` to
  obtain a Unicode string from an array of some other type.

The string representation of array objects has the form array(typecode, initializer). The initializer is omitted if the array is empty, otherwise it is a Unicode string if the typecode is 'u' or 'w', otherwise it is a list of numbers. The string representation is guaranteed to be able to be converted back to an array with the same type and value using :func:eval, so long as the :class:~array.array class has been imported using from array import array. Variables inf and nan must also be defined if it contains corresponding floating-point values. Examples::

array('l') array('w', 'hello \u2641') array('l', [1, 2, 3, 4, 5]) array('d', [1.0, 2.0, 3.14, -inf, nan])

.. seealso::

Module :mod:struct Packing and unpacking of heterogeneous binary data.

NumPy <https://numpy.org/>_ The NumPy package defines another array type.

.. _ieee 754 standard: https://en.wikipedia.org/wiki/IEEE_754-2008_revision