I'm looking at it from the angle of someone that has spent over a decade in and out of C. The code in the loop is in NO way an "artifact", it's absolutely critical to the comparison. My example in no way removes the essence, especially if we are using "idioms".

I said the loop is an artifact, not the code in the loop. Their experimental design is "Do x N times, then divide the overall runtime of the program by N to estimate the cost of x." If timing a program that did x once lead to good results, they would do that - but it doesn't, so they don't. You're trying to optimize around the loop, but by doing that, you're changing the x that is being measured.

Two things potentially different between the two implementations:

1. The C code is stack allocating a pointer in every loop iteration.

2. Cleaning up the memory without(potentially) triggering Python's GC.

Is the Python GC getting triggered in this scenario? If not, then this is what's actually happening, with the cleanup happening automatically when the process exits:

  char x[10000000];
  int i;

  for (i = 0; i < 10000000; i++) {
        x[i] = malloc(44 * sizeof(char));
        sprintf(x, "%d %d", i, i);
    }

If GC is thrown into the mix, the C code is really:

  char x[1000];
  int i;
  int j=0;
  for (i = 0; i < 10000000; i++) {
        x[j] = malloc(44 * sizeof(char));
        sprintf(x, "%d %d", i, i);
        j++;
        if(j == 1000) {
            for(j = 0; j < 1000; ++j)
                free(x[j]);
        }
    }