Read integer from binary file in Python

Question

I have the following snippet of C code:

#include <stdio.h>
void main(){
 int a = 1308901095;
 FILE *fp;
 fp = fopen("file", "wb");
 fwrite(&a, sizeof(int), 1, fp);
 fclose(fp);
 printf("Done\n");
}

This will write the "a" integer in file "file", in binary form.

How I can read this number in Python?

• csl: Small tip: If you're transferring this binary file between computers, be sure to consider endianness and the size of your int.

Answer 1

Try following.

from struct import *
f = open('file', 'rb')
print unpack('<i', f.read(4))[0]
f.close()

note that using '<' about your machine is little endian or not.

• Léo Germond: You should replace '>' or '<' by '@' to use native endianess. Source: docs.python.org/library/…
• johnsyweb: @Leo: Presuming the file is being read by the same machine (architecture) as the one that did the writing.
• Léo Germond: @john, Yes tou are totally right about that, I was just "completing" your answer.