: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. Arrays are 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:

Notes:

1. The 'u' type code corresponds to Python's obsolete unicode character (:c:type:`Py_UNICODE` which is :c:type:`wchar_t`). Depending on the platform, it can be 16 bits or 32 bits.

   'u' will be removed together with the rest of the :c:type:`Py_UNICODE` API.

   .. deprecated-removed:: 3.3 4.0
   
   

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:`itemsize` attribute.

The module defines the following type:

A new array whose items are restricted by typecode, and initialized from the optional initializer value, which must be a list, a :term:`bytes-like object`, or iterable over elements of the appropriate type.

If given a list or string, the initializer is passed to the new array's :meth:`fromlist`, :meth:`frombytes`, or :meth:`fromunicode` method (see below) to add initial items to the array. Otherwise, the iterable initializer is passed to the :meth:`extend` method.

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

.. data:: typecodes

 A string with all available type codes.

Array objects support the ordinary 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.

The following data items and methods are also supported:

.. attribute:: array.typecode

 The typecode character used to create the array.

.. attribute:: array.itemsize

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

.. method:: array.append(x)

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

.. method:: array.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:: array.byteswap()

 "Byteswap" all items of the array. This is only supported for values which are
 1, 2, 4, or 8 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.

.. method:: array.count(x)

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

.. method:: array.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:: array.frombytes(s)

 Appends items from the string, interpreting the string 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:: array.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. *f* must be a real built-in file object; something
 else with a :meth:`read` method won't do.

.. method:: array.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:: array.fromstring()

 Deprecated alias for :meth:`frombytes`.

 .. deprecated-removed:: 3.2 3.9

.. method:: array.fromunicode(s)

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

.. method:: array.index(x)

 Return the smallest *i* such that *i* is the index of the first occurrence of
 *x* in the array.

.. method:: array.insert(i, x)

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

.. method:: array.pop([i])

 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:: array.remove(x)

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

.. method:: array.reverse()

 Reverse the order of the items in the array.

.. method:: array.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:: array.tofile(f)

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

.. method:: array.tolist()

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

.. method:: array.tostring()

 Deprecated alias for :meth:`tobytes`.

 .. deprecated-removed:: 3.2 3.9

.. method:: array.tounicode()

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

When an array object is printed or converted to a string, it is represented as array(typecode, initializer). The initializer is omitted if the array is empty, otherwise it is a string if the typecode is 'u', otherwise it is a list of numbers. The string 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. Examples:

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

.. seealso::

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

 Module :mod:`xdrlib`
 Packing and unpacking of External Data Representation (XDR) data as used in some
 remote procedure call systems.

 `The Numerical Python Documentation <https://docs.scipy.org/doc/>`_
 The Numeric Python extension (NumPy) defines another array type; see
 http://www.numpy.org/ for further information about Numerical Python.

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