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(python2.1-lib.info)array
Efficient arrays of numeric values
==================================
Efficient arrays of uniformly typed numeric values.
This module defines a new object type which can efficiently 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 "type code", which is a
single character. The following type codes are defined:
Type code C Type Minimum size in bytes
------ ----- -----
'c' character 1
'b' signed int 1
'B' unsigned int 1
'h' signed int 2
'H' unsigned int 2
'i' signed int 2
'I' unsigned int 2
'l' signed int 4
'L' unsigned int 4
'f' float 4
'd' double 8
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 `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 function and type object:
`array(typecode[, initializer])'
Return a new array whose items are restricted by TYPECODE, and
initialized from the optional INITIALIZER value, which must be a
list or a string. The list or string is passed to the new array's
`fromlist()' or `fromstring()' method (see below) to add initial
items to the array.
`ArrayType'
Type object corresponding to the objects returned by `array()'.
Array objects support the following data items and methods:
`typecode'
The typecode character used to create the array.
`itemsize'
The length in bytes of one array item in the internal
representation.
`append(x)'
Append a new item with value X to the end of the array.
`buffer_info()'
Return a tuple `(ADDRESS, LENGTH)' giving the current memory
address and the length in bytes of the buffer used to hold array's
contents. 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.
`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(x)'
Return the number of occurences of X in the array.
`extend(a)'
Append array items from A to the end of the array.
`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. F must be a real built-in file object;
something else with a `read()' method won't do.
`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.
`fromstring(s)'
Appends items from the string, interpreting the string as an array
of machine values (i.e. as if it had been read from a file using
the `fromfile()' method).
`index(x)'
Return the smallest I such that I is the index of the first
occurence of X in the array.
`insert(i, x)'
Insert a new item with value X in the array before position I.
`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.
`read(f, n)'
_This is deprecated in Python 1.5.1. Use the `fromfile()' method._
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. F must be a real built-in file object;
something else with a `read()' method won't do.
`remove(x)'
Remove the first occurence of X from the array.
`reverse()'
Reverse the order of the items in the array.
`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.
`tostring()'
Convert the array to an array of machine values and return the
string representation (the same sequence of bytes that would be
written to a file by the `tofile()' method.)
`write(f)'
_This is deprecated in Python 1.5.1. Use the `tofile()' method._
Write all items (as machine values) to the file object F.
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 reverse quotes (```'), so long as the `array()' function
has been imported using `from array import array'. Examples:
array('l')
array('c', 'hello world')
array('l', [1, 2, 3, 4, 5])
array('d', [1.0, 2.0, 3.14])
See also:
Note: struct Packing and unpacking of heterogeneous binary data.
Note: xdrlib Packing and unpacking of External Data
Representation (XDR) data as used in some remote procedure call
systems. `The Numerical Python Manual'{The Numeric Python
extension (NumPy) defines another array type; see
<http://numpy.sourceforge.net/> for further information about
Numerical Python. (A PDF version of the NumPy manual is available
at <http://numpy.sourceforge.net/numdoc/numdoc.pdf>.}
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