array — Efficient arrays of numeric valuesThis 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 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 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:
array.array(typecode[, initializer])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.
Changed in version 2.4: Formerly, only lists or strings were accepted.
If given a list or string, the initializer is passed to the new array’s
fromlist(), fromstring(), or fromunicode() method (see below)
to add initial items to the array. Otherwise, the iterable initializer is
passed to the extend() method.
array.ArrayTypearray.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:
array.typecodearray.itemsizearray.append(x)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 Buffers and Memoryview Objects.
array.byteswap()RuntimeError is raised. It is useful when reading data from a file written on a machine with a different byte order.array.count(x)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.
Changed in version 2.4: Formerly, the argument could only be another array.
array.fromfile(f, n)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.array.fromlist(list)for x in list: a.append(x) except that if there is a type error, the array is unchanged.array.fromstring(s)fromfile() method).array.fromunicode(s)'u' array; otherwise a ValueError is raised. Use array.fromstring(unicodestring.encode(enc)) to append Unicode data to an array of some other type.array.index(x)array.insert(i, x)array.pop([i])-1, so that by default the last item is removed and returned.array.read(f, n)Deprecated since version 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.
array.remove(x)array.reverse()array.tofile(f)array.tolist()array.tostring()tofile() method.)array.tounicode()'u' array; otherwise a ValueError is raised. Use array.tostring().decode(enc) to obtain a unicode string from an array of some other type.array.write(f)Deprecated since version 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 eval(), so long as the
array class 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])
See also
structxdrlib