sum_sentence.c

#include <Python.h>

/*
  Return the sum of word lengths of all words (unicode strings) in the list `sentence`.
  Return -1 if `sentence` isn't a list, and -2 if any of its elements is not a unicode string.
  
  `sentence` and its elements are const = never changed inside this function, and guaranteed to live
  throughout its execution, so we don't bother updating any reference counts.
*/
static long long process_const_sentence(PyObject *sentence) {
    if (!PyList_Check(sentence)) {
        return -1;
    }

    Py_ssize_t pos = 0;
    long long result = 0;
    for (; pos < PyList_Size(sentence); pos++) {
        PyObject *word = PyList_GET_ITEM(sentence, pos);
        if (!PyUnicode_Check(word)) {
            return -2;
        }
        result += PyUnicode_GET_SIZE(word);
    }
    return result;
}