7.1. struct

: Lib/struct.py

Python Python bytes C C Python

C C (alignment) C native standard :

struct ( Struct ) buffer (buffer Protocol) bytes bytearray bytes

7.1.1.

:

exception struct.error

struct.pack(fmt, v1, v2, ...)

fmt v1, v2,

struct.pack_into(fmt, buffer, offset, v1, v2, ...)

fmt v1, v2, buffer offset

struct.unpack(fmt, buffer)

(pack(fmt, ...) ) buffer fmt calcsize()

struct.unpack_from(fmt, buffer, offset=0)

buffer offset fmt offset calcsize()

struct.iter_unpack(fmt, buffer)

buffer fmt calcsize()

yield

3.4 .

struct.calcsize(fmt)

fmt ( pack(fmt, ...) )

7.1.2.

/

7.1.2.1.

C (native) (byte order) (alignment) ( C )

:
@ native native native
= native standard none
< standard none
> standard none
! (= ) standard none

'@'

Intel x86 AMD64 (x86-64) Motorola 68000 PowerPC G5 ARM Intel Itanium () sys.byteorder

C sizeof

'@' '=' :

'!'

()'<' '>'

:

  2. ( '<', '>', '=', '!' )

7.1.2.2.

(format character) ; C Python : standard '<', '>', '!', '=' native

C Python
x    
c char 1 1  
b signed char 1 (1),(3)
B unsigned char 1 (3)
? _Bool (bool) 1 (1)
h short 2 (3)
H unsigned short 2 (3)
i int 4 (3)
I unsigned int 4 (3)
l long 4 (3)
L unsigned long 4 (3)
q long long 8 (2), (3)
Q unsigned long long 8 (2), (3)
n ssize_t   (4)
N size_t   (4)
e (7) 2 (5)
f float 4 (5)
d double 8 (5)
s char[] bytes    
p char[] bytes    
P void *   (6)

3.3 : 'n' 'N'

3.6 : 'e'

:

  1. '?' C99 _Bool char 1

  2. 'q' 'Q' C C long long Windows __int64

  3. __index__()

    3.2 : __index__() 3.2

  4. 'n' 'N' ( '@' ) native standard

  5. 'f' 'd' 'e' IEEE 754 binary32 ('f' ) binary64 ('d' ) binary16('e' )

  6. 'P' ('@' )'=' struct 'P'

  7. IEEE 754 binary16 "" IEEE 754 standard 2008 bit 5 bit 11 bit ( 10 bit ) 6.1e-05 6.5e+04 C : unsigned short Wikipedia half-precision floating-point format

(count) '4h' 'hhhh'

; count

's' (count) '10s' 10 '10c' 10 1 null '0s' '0c' 0

('b', 'B', 'h', 'H', 'i', 'I', 'l', 'L', 'q', 'Q') x x struct.error

3.1 : 3.0 struct.error DeprecationWarning

'p' "Pascal (pascal string)" Pascal count 1 255 pack() Pascal (count-1 ) count-1 count-1 count unpack() 'p' count 255

'?' True False 0 1 True

7.1.2.3.

/:

>>> from struct import *
>>> pack('hhl', 1, 2, 3)
b'\x00\x01\x00\x02\x00\x00\x00\x03'
>>> unpack('hhl', b'\x00\x01\x00\x02\x00\x00\x00\x03')
(1, 2, 3)
>>> calcsize('hhl')
8

named tuple :

>>> record = b'raymond   \x32\x12\x08\x01\x08'
>>> name, serialnum, school, gradelevel = unpack('<10sHHb', record)

>>> from collections import namedtuple
>>> Student = namedtuple('Student', 'name serialnum school gradelevel')
>>> Student._make(unpack('<10sHHb', record))
Student(name=b'raymond   ', serialnum=4658, school=264, gradelevel=8)

:

>>> pack('ci', b'*', 0x12131415)
b'*\x00\x00\x00\x12\x13\x14\x15'
>>> pack('ic', 0x12131415, b'*')
b'\x12\x13\x14\x15*'
>>> calcsize('ci')
8
>>> calcsize('ic')
5

'llh0l' long 4 2 :

>>> pack('llh0l', 1, 2, 3)
b'\x00\x00\x00\x01\x00\x00\x00\x02\x00\x03\x00\x00'

array
xdrlib
XDR

7.1.3.

struct :

class struct.Struct(format)

format Struct Struct struct

Struct :

pack(v1, v2, ...)

pack() (len(result) size )

pack_into(buffer, offset, v1, v2, ...)

pack_into()

unpack(buffer)

unpack() (buffer size )

unpack_from(buffer, offset=0)

unpack_from() (buffer - offset size )

iter_unpack(buffer)

iter_unpack() (buffer size )

3.4 .

format

Struct

size

format ( pack() )