"array" — Efficient arrays of numeric values
********************************************

======================================================================

This module defines an object type which can compactly represent an
array of basic values: characters, integers, floating-point numbers.
Arrays are mutable *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 *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                       |         |
+-------------+----------------------+---------------------+-------------------------+---------+
| "'f'"       | float                | float               | 4                       |         |
+-------------+----------------------+---------------------+-------------------------+---------+
| "'d'"       | double               | float               | 8                       |         |
+-------------+----------------------+---------------------+-------------------------+---------+

Notes:

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

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

   Deprecated since version 3.3, will be removed in version 3.16:
   Please migrate to "'w'" typecode.

2. Added in version 3.13.

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 "array.itemsize" attribute.

The module defines the following item:

array.typecodes

   A string with all available type codes.

The module defines the following type:

class array.array(typecode[, initializer])

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

   If given a "bytes" or "bytearray" object, the initializer is passed
   to the new array’s "frombytes()" method; if given a Unicode string,
   the initializer is passed to the "fromunicode()" method; otherwise,
   the initializer’s iterator is passed to the "extend()" method to
   add initial items to the array.

   Array objects support the ordinary mutable *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, "TypeError" is raised.
   Array objects also implement the buffer interface, and may be used
   wherever *bytes-like objects* are supported.

   Arrays are generic over the type of their contents.

   Raises an auditing event "array.__new__" with arguments "typecode",
   "initializer".

   typecode

      The typecode character used to create the array.

   itemsize

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

   append(value, /)

      Append a new item with the specified value to the end of the
      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 "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 Buffer Protocol.

   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, "RuntimeError" is raised.  It is useful when reading
      data from a file written on a machine with a different byte
      order.

   count(value, /)

      Return the number of occurrences of *value* in the 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, "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.

   frombytes(buffer, /)

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

      Added in version 3.2: "fromstring()" is renamed to "frombytes()"
      for clarity.

   fromfile(f, n, /)

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

   fromunicode(ustr, /)

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

   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 "ValueError" if *value* is not
      found.

      Changed in version 3.10: Added optional *start* and *stop*
      parameters.

   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.

   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.

   remove(value, /)

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

   clear()

      Remove all elements from the array.

      Added in version 3.13.

   reverse()

      Reverse the order of the items in the 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 "tofile()" method.)

      Added in version 3.2: "tostring()" is renamed to "tobytes()" for
      clarity.

   tofile(f, /)

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

   tolist()

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

   tounicode()

      Convert the array to a Unicode string.  The array must have a
      type "'u'" or "'w'"; otherwise a "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 "eval()", so long as the
"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])

See also:

  Module "struct"
     Packing and unpacking of heterogeneous binary data.

  NumPy
     The NumPy package defines another array type.
