struct.rst

:mod:`struct` -- pack and unpack primitive data types

.. module:: struct
   :synopsis: pack and unpack primitive data types

|see_cpython_module| :mod:`python:struct`.

The following byte orders are supported:

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

The following data types are supported:

Format	C Type	Python type	Standard size
b	signed char	integer	1
B	unsigned char	integer	1
h	short	integer	2
H	unsigned short	integer	2
i	int	integer (1<fn>)	4
I	unsigned int	integer (1<fn>)	4
l	long	integer (1<fn>)	4
L	unsigned long	integer (1<fn>)	4
q	long long	integer (1<fn>)	8
Q	unsigned long long	integer (1<fn>)	8
f	float	float (2<fn>)	4
d	double	float (2<fn>)	8
s	char[]	bytes
P	void *	integer

1. Requires long support when used with values larger than 30 bits.
2. Requires floating point support.

Difference to CPython

Whitespace is not supported in format strings.

Functions

.. function:: calcsize(fmt)

   Return the number of bytes needed to store the given *fmt*.

.. function:: pack(fmt, v1, v2, ...)

   Pack the values *v1*, *v2*, ... according to the format string *fmt*.
   The return value is a bytes object encoding the values.

.. function:: pack_into(fmt, buffer, offset, v1, v2, ...)

   Pack the values *v1*, *v2*, ... according to the format string *fmt*
   into a *buffer* starting at *offset*. *offset* may be negative to count
   from the end of *buffer*.

.. function:: unpack(fmt, data)

   Unpack from the *data* according to the format string *fmt*.
   The return value is a tuple of the unpacked values.

.. function:: unpack_from(fmt, data, offset=0, /)

   Unpack from the *data* starting at *offset* according to the format string
   *fmt*. *offset* may be negative to count from the end of *data*. The return
   value is a tuple of the unpacked values.