Python struct.pack()函数用法解析

struct — Interpret bytes as packed binary data

将字节解释为压缩二进制数据

Source code: Lib/struct.py

Functions and Exceptions

 

struct.pack(format, v1, v2, ...)

Return a bytes object containing the values v1, v2, … packed according to the format string format. The arguments must match the values required by the format exactly.

返回一个字节对象，该对象包含根据格式字符串格式打包的值v1、v2，…。参数必须与格式要求的值完全匹配。

第一个参数是后面所有参数的格式字符串，后面的每个参数必须与格式字符串描述一致。

eg:h表示short，l表示long； 'hhl'表示后面有三个参数，依次是short，short，long类型

 c表示 char，bytes of length 1（长度的byte数组），i表示integer 整数；'ci'表示后面有两个个参数，依次是char，integer 类型

>>> from struct import *
>>> pack('hhl', 1, 2, 3)
>>> pack('ci', b'*', 0x12131415)

 

 

Format Strings

Format strings are the mechanism used to specify the expected layout when packing and unpacking data. They are built up from Format Characters, which specify the type of data being packed/unpacked. In addition, there are special characters for controlling the Byte Order, Size, and Alignment.

格式字符串是用于在打包和解包数据时指定预期布局的机制。它们由格式字符组成，这些字符指定要打包/解包的数据类型。此外，还有用于控制字节顺序、大小和对齐的特殊字符。

 

Character	Byte order	Size	Alignment
@	native	native	native
=	native	standard	none
<	little-endian	standard	none
>	big-endian	standard	none
!	network (= big-endian)	standard	none

1. Format Characters

Format characters have the following meaning; the conversion between C and Python values should be obvious given their types. The ‘Standard size’ column refers to the size of the packed value in bytes when using standard size; that is, when the format string starts with one of '<', '>', '!' or '='. When using native size, the size of the packed value is platform-dependent.

格式字符具有以下含义；鉴于C和python值的类型，它们之间的转换应该是显而易见的。“标准大小”列是指使用标准大小时压缩值的字节大小；也就是说，当格式字符串以“<”、“>”、“！”之一开头时或'='。使用本机大小时，打包值的大小取决于平台。

 

Format	C Type	Python type	Standard size	Notes
x	pad byte	no value
c	char	bytes of length 1	1
b	signed char	integer	1	(1),(3)
B	unsigned char	integer	1	(3)
?	_Bool	bool	1	(1)
h	short	integer	2	(3)
H	unsigned short	integer	2	(3)
i	int	integer	4	(3)
I	unsigned int	integer	4	(3)
l	long	integer	4	(3)
L	unsigned long	integer	4	(3)
q	long long	integer	8	(2), (3)
Q	unsigned long long	integer	8	(2), (3)
n	ssize_t	integer		(4)
N	size_t	integer		(4)
e	(7)	float	2	(5)
f	float	float	4	(5)
d	double	float	8	(5)
s	char[]	bytes
p	char[]	bytes
P	void *	integer		(6)