#define CHUNK_SIZE 8192

/* Consume a "file-like" object and write bytes to stdout */
static PyObject *py_consume_file(PyObject *self, PyObject *args) {
 PyObject *obj;
 PyObject *read_meth;
 PyObject *result = NULL;
 PyObject *read_args;

 if (!PyArg_ParseTuple(args,"O", &obj)) {
  return NULL;
 }

 /* Get the read method of the passed object */
 if ((read_meth = PyObject_GetAttrString(obj, "read")) == NULL) {
  return NULL;
 }

 /* Build the argument list to read() */
 read_args = Py_BuildValue("(i)", CHUNK_SIZE);
 while (1) {
  PyObject *data;
  PyObject *enc_data;
  char *buf;
  Py_ssize_t len;

  /* Call read() */
  if ((data = PyObject_Call(read_meth, read_args, NULL)) == NULL) {
   goto final;
  }

  /* Check for EOF */
  if (PySequence_Length(data) == 0) {
   Py_DECREF(data);
   break;
  }

  /* Encode Unicode as Bytes for C */
  if ((enc_data=PyUnicode_AsEncodedString(data,"utf-8","strict"))==NULL) {
   Py_DECREF(data);
   goto final;
  }

  /* Extract underlying buffer data */
  PyBytes_AsStringAndSize(enc_data, &buf, &len);

  /* Write to stdout (replace with something more useful) */
  write(1, buf, len);

  /* Cleanup */
  Py_DECREF(enc_data);
  Py_DECREF(data);
 }
 result = Py_BuildValue("");

 final:
 /* Cleanup */
 Py_DECREF(read_meth);
 Py_DECREF(read_args);
 return result;
}

>>> import io
>>> f = io.StringIO('Hello\nWorld\n')
>>> import sample
>>> sample.consume_file(f)
Hello
World
>>>

...
/* Call read() */
if ((data = PyObject_Call(read_meth, read_args, NULL)) == NULL) {
 goto final;
}

/* Check for EOF */
if (PySequence_Length(data) == 0) {
 Py_DECREF(data);
 break;
}
if (!PyBytes_Check(data)) {
 Py_DECREF(data);
 PyErr_SetString(PyExc_IOError, "File must be in binary mode");
 goto final;
}

/* Extract underlying buffer data */
PyBytes_AsStringAndSize(data, &buf, &len);
...