Original link: Python is Faster than C / LinkedIn.
That C code is extreemly inefficient. Pretty easy to make Python faster than C if the C code is this bad.
Reading a file with single char read (getc). The constant copying of data within the window variable. That is guaranteed to be slow.
Functionally I am also skeptical about the while(!feof(fp)) construct - I would have preferred while((c = getc(fp)) >= 0) {.