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Python Library Reference |  |
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This module defines an 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 | 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 |
'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 |
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 type:
| typecode[, initializer]) |
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, 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:
| x) |
| ) |
(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 the Python/C API Reference Manual.
| ) |
| x) |
| a) |
| f, n) |
| list) |
| s) |
| s) |
| x) |
| i, x) |
| [i]) |
-1, so that by default
the last item is removed and returned.
| 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.
| x) |
| ) |
| f) |
| ) |
| ) |
| ) |
| f) |
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('u', u'hello \textbackslash u2641')
array('l', [1, 2, 3, 4, 5])
array('d', [1.0, 2.0, 3.14])
See Also:
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Python Library Reference | |
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