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:mod:`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 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
'c' char character 1
'b' signed char int 1
'B' unsigned char int 1
'u' Py_UNICODE Unicode character 2 (see note)
'h' signed short int 2
'H' unsigned short int 2
'i' signed int int 2
'I' unsigned int long 2
'l' signed long int 4
'L' unsigned long long 4
'f' float float 4
'd' double float 8

Note

The 'u' typecode corresponds to Python's unicode character. On narrow Unicode builds this is 2-bytes, on wide builds this is 4-bytes.

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 values stored for 'L' and 'I' items will be represented as Python long integers when retrieved, because Python's plain integer type cannot represent the full range of C's unsigned (long) integers.

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, string, 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:`fromstring`, or :meth:`fromunicode` method (see below) to add initial items to the array. Otherwise, the iterable initializer is passed to the :meth:`extend` method.

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 buffer objects are supported.

The following data items and methods are also supported:

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 'c', 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 :func:`array` function has been imported using from array import array. Examples:

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