diff options
Diffstat (limited to 'Doc/api/intro.tex')
-rw-r--r-- | Doc/api/intro.tex | 33 |
1 files changed, 11 insertions, 22 deletions
diff --git a/Doc/api/intro.tex b/Doc/api/intro.tex index 1295e5f..80650fe 100644 --- a/Doc/api/intro.tex +++ b/Doc/api/intro.tex @@ -225,25 +225,10 @@ immutable data type. You should only use \cfunction{PyTuple_SetItem()} for tuples that you are creating yourself. -Equivalent code for populating a list can be written using -\cfunction{PyList_New()} and \cfunction{PyList_SetItem()}. Such code -can also use \cfunction{PySequence_SetItem()}; this illustrates the -difference between the two (the extra \cfunction{Py_DECREF()} calls): +Equivalent code for populating a list can be written using +\cfunction{PyList_New()} and \cfunction{PyList_SetItem()}. -\begin{verbatim} -PyObject *l, *x; - -l = PyList_New(3); -x = PyInt_FromLong(1L); -PySequence_SetItem(l, 0, x); Py_DECREF(x); -x = PyInt_FromLong(2L); -PySequence_SetItem(l, 1, x); Py_DECREF(x); -x = PyString_FromString("three"); -PySequence_SetItem(l, 2, x); Py_DECREF(x); -\end{verbatim} - -You might find it strange that the ``recommended'' approach takes more -code. However, in practice, you will rarely use these ways of +However, in practice, you will rarely use these ways of creating and populating a tuple or list. There's a generic function, \cfunction{Py_BuildValue()}, that can create most common objects from C values, directed by a \dfn{format string}. For example, the @@ -251,10 +236,10 @@ above two blocks of code could be replaced by the following (which also takes care of the error checking): \begin{verbatim} -PyObject *t, *l; +PyObject *tuple, *list; -t = Py_BuildValue("(iis)", 1, 2, "three"); -l = Py_BuildValue("[iis]", 1, 2, "three"); +tuple = Py_BuildValue("(iis)", 1, 2, "three"); +list = Py_BuildValue("[iis]", 1, 2, "three"); \end{verbatim} It is much more common to use \cfunction{PyObject_SetItem()} and @@ -276,8 +261,12 @@ set_all(PyObject *target, PyObject *item) if (n < 0) return -1; for (i = 0; i < n; i++) { - if (PyObject_SetItem(target, i, item) < 0) + PyObject *index = PyInt_FromLong(i); + if (!index) + return -1; + if (PyObject_SetItem(target, index, item) < 0) return -1; + Py_DECREF(index); } return 0; } |