How to unpack bytes using struct module in python?

Question

I'm trying to unpack bytes in python :-

import struct


c_struct_exp='struct lokesh { int i=5;} lm;'
result=struct.unpack('!i',bytes(c_struct_exp,'utf-8'))  
print(result)

error:

 struct.error: unpack requires a bytes object of length 4

please, help me with format string expression in unpack method.

Nikolai Fetissov · Accepted Answer · 2013-01-25 13:23:13Z

3

unpack is for unpacking binary data, not C source code. To follow your example of single integer member structure:

>>> from struct import *
>>> pack('i', 134)
'\x86\x00\x00\x00'
>>> unpack('i', '\x86\x00\x00\x00')
(134,)
>>>

answered Jan 25, 2013 at 13:23

Nikolai Fetissov

84.6k13 gold badges118 silver badges175 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Lokesh Kumar Over a year ago

I'm not using C source code directly. I'm converting c source code into raw bytes :- bytes(c_struct_exp,'utf-8') before using it in unpack methode..

Nikolai Fetissov Over a year ago

Try printing the output of your bytes(...) call - it's still source code. unpack decodes memory image of a structure, not its source description.

Lokesh Kumar Over a year ago

okk :) got it... actually i'm trying to decode a C struct packet from a C client at server side(python receiving end).. how can i can decode unpack received raw bytes(C struct,which is memory image and not a source code at client side)... how can i unpack a structure of the above type :-

typedef struct packet{ int command; union{ struct{int data[100]; int ttl[100];}; struct{ char config[256]; };};} myPacketStruct;

Collectives™ on Stack Overflow

How to unpack bytes using struct module in python?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related