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 | Notes |
---|---|---|---|---|
'b'
|
signed char | int | 1 | |
'B'
|
unsigned char | int | 1 | |
'u'
|
wchar_t | Unicode character | 2 | (1) |
'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:
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 to its behavior because
Py_UNICODE
is alias of wchar_t
since Python 3.3.
Deprecated since version 3.3, will be removed in version 4.0.
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 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, a bytes-like object, or iterable over elements of the appropriate type.
If given a list or string, the initializer is passed to the new array’s
fromlist()
, frombytes()
, or fromunicode()
method (see below)
to add initial items to the array. Otherwise, the iterable initializer is
passed to the extend()
method.
Raises an auditing event array.__new__
with arguments typecode
, initializer
.
array.
typecodes
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 bytes-like objects are supported.
The following data items and methods are also supported:
array.
typecode
array.
itemsize
array.
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 Buffer Protocol.
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)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.array.
frombytes
(s)Appends items from the string, interpreting the string as an array of machine
values (as if it had been read from a file using the fromfile()
method).
New in version 3.2: fromstring()
is renamed to frombytes()
for clarity.
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.
fromunicode
(s)'u'
array; otherwise a ValueError
is raised. Use array.frombytes(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.
remove
(x)array.
reverse
()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.)
New in version 3.2: tostring()
is renamed to tobytes()
for clarity.
array.
tofile
(f)array.
tolist
()array.
tounicode
()'u'
array; otherwise a ValueError
is raised. Use array.tobytes().decode(enc)
to obtain a unicode string from an array of some other type.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 'u'
, 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('u', 'hello \u2641')
array('l', [1, 2, 3, 4, 5])
array('d', [1.0, 2.0, 3.14])
See also
struct
xdrlib