Simple demo of how to write structs from C and read them in Python.

Makefile

write: write.c
	gcc $< -o $@

test: write
	./write
	python read.py

read.py

#!/usr/bin/env python

from construct import Struct, Int32un, Float32n

print '--- not nested ---'
x = Struct('c' / Int32un, 'x' / Float32n)
with open('out.raw', 'rb') as f:
    result = []
    while True:
        buf = f.read(x.sizeof())
        if len(buf) != x.sizeof():
            break
        result.append(x.parse(buf))
    print result

print '--- nested ---'
y = Struct('a' / Int32un, 's' / x)
with open('out_nested.raw', 'rb') as f:
    result = []
    while True:
        buf = f.read(y.sizeof())
        if len(buf) != y.sizeof():
            break
        result.append(y.parse(buf))
    print result

write.c

#include <stdio.h>

typedef struct MyStruct {
  int c;
  float x;
} MyStruct_t;

typedef struct MyStructNested {
  int a;
  MyStruct_t s;
} MyStructNested_t;
  
int main(void) {
  int n = 3;
  MyStruct_t m[n];
  m[0].c = 1; m[0].x = 3.5;
  m[1].c = 2; m[1].x = 7.2;
  m[2].c = 3; m[2].x = 1.9;

  FILE * f = fopen("out.raw", "wb");
  for (int i = 0; i < n; i++) {
    fwrite(&m[i], sizeof(MyStruct_t), 1, f);
  }
  fclose(f);

  MyStructNested_t mn[n];
  mn[0].a = 1;
  mn[0].s.c = 2;
  mn[0].s.x = 3.5;

  mn[1].a = 2;
  mn[1].s.c = 4;
  mn[1].s.x = 1.7;

  mn[2].a = 3;
  mn[2].s.c = 0;
  mn[2].s.x = 2.9;

  f = fopen("out_nested.raw", "wb");
  for (int i = 0; i < n; i++) {
    fwrite(&mn[i], sizeof(MyStructNested_t), 1, f);
  }
  fclose(f);  
}