array
— 高效数值数组
¶
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 type code , which is a single character. The following type codes are defined:
| Type code | C 类型 | Python Type | Minimum size in bytes | 注意事项 |
|---|---|---|---|---|
'b'
|
signed char | int | 1 | |
'B'
|
unsigned char | int | 1 | |
'u'
|
Py_UNICODE | Unicode character | 2 | (1) |
'h'
|
signed short | int | 2 | |
'H'
|
unsigned short | int | 2 | |
'i'
|
signed int | int | 2 | |
'I'
|
无符号 int | int | 2 | |
'l'
|
signed long | int | 4 | |
'L'
|
unsigned long | int | 4 | |
'q'
|
signed long long | int | 8 | (2) |
'Q'
|
unsigned long long | int | 8 | (2) |
'f'
|
float | float | 4 | |
'd'
|
double | float | 8 |
注意事项：
'u'
type code corresponds to Python’s obsolete unicode character (
Py_UNICODE
which is
wchar_t
). Depending on the platform, it can be 16 bits or 32 bits.
'u'
will be removed together with the rest of the
Py_UNICODE
API.
Deprecated since version 3.3, will be removed in version 4.0.
'q'
and
'Q'
type codes are available only if the platform C compiler used to build Python supports C
long
long
, or, on Windows,
__int64
.
3.3 版新增。
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
属性。
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 像字节对象 , 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()
，或
fromunicode()
method (see below) to add initial items to the array. Otherwise, the iterable initializer is passed to the
extend()
方法。
array.
typecodes
¶
A string with all available type codes.
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
像字节对象
are supported.
The following data items and methods are also supported:
array.
typecode
¶
The typecode character used to create the array.
array.
itemsize
¶
The length in bytes of one array item in the internal representation.
array.
append
(
x
)
¶
Append a new item with value x to the end of the array.
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.
注意
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 缓冲协议 .
array.
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.
array.
count
(
x
)
¶
Return the number of occurrences of x in the array.
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.
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()
方法)。
3.2 版新增：
fromstring()
is renamed to
frombytes()
for clarity.
array.
fromfile
(
f
,
n
)
¶
Read
n
items (as machine values) from the
文件对象
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.
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.
array.
fromstring
(
)
¶
Deprecated alias for
frombytes()
.
array.
fromunicode
(
s
)
¶
Extends this array with data from the given unicode string. The array must be a type
'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
)
¶
Return the smallest i 这样 i is the index of the first occurrence of x in the array.
array.
insert
(
i
,
x
)
¶
Insert a new item with value x in the array before position i . Negative values are treated as being relative to the end of the array.
array.
pop
(
[
i
]
)
¶
Removes the item with the index
i
from the array and returns it. The optional argument defaults to
-1
，因此默认情况下，最后项会被移除并返回。
array.
remove
(
x
)
¶
Remove the first occurrence of x from the array.
array.
reverse
(
)
¶
Reverse the order of the items in the array.
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.)
3.2 版新增：
tostring()
is renamed to
tobytes()
for clarity.
array.
tolist
(
)
¶
Convert the array to an ordinary list with the same items.
array.
tounicode
(
)
¶
Convert the array to a unicode string. The array must be a type
'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)
。
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])
另请参阅
struct
xdrlib