traverseda
/
cpython
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Added optional None arguments to itertools.islice().

This commit is contained in:
Raymond Hettinger 2004-12-05 09:25:51 +00:00
parent d2f70cbe8e
commit b2594050ea
4 changed files with 27 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Doc/lib/libitertools.tex
View File

@ -261,6 +261,11 @@ by functions or loops that truncate the stream.
yield element
next += step
\end{verbatim}
If \var{start} is \code{None}, then iteration starts at zero.
If \var{step} is \code{None}, then the step defaults to one.
\versionchanged[accept \code{None} values for default \var{start} and
\var{step}]{2.5}
\end{funcdesc}
\begin{funcdesc}{izip}{*iterables}

2
Lib/test/test_itertools.py
View File

@ -260,6 +260,8 @@ class TestBasicOps(unittest.TestCase):
# Test stop=None
self.assertEqual(list(islice(xrange(10), None)), range(10))
self.assertEqual(list(islice(xrange(10), None, None)), range(10))
self.assertEqual(list(islice(xrange(10), None, None, None)), range(10))
self.assertEqual(list(islice(xrange(10), 2, None)), range(2, 10))
self.assertEqual(list(islice(xrange(10), 1, None, 2)), range(1, 10, 2))

4
Misc/NEWS
View File

@ -17,6 +17,10 @@ Core and builtins
Extension Modules
-----------------
- itertools.islice() now accepts None for the start and step arguments.
This allows islice() to work more readily with slices:
islice(s.start, s.stop, s.step)
Library
-------

30
Modules/itertoolsmodule.c
View File

@ -1044,14 +1044,14 @@ islice_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
PyObject *seq;
long start=0, stop=-1, step=1;
PyObject *it, *a1=NULL, *a2=NULL;
PyObject *it, *a1=NULL, *a2=NULL, *a3=NULL;
int numargs;
isliceobject *lz;
numargs = PyTuple_Size(args);
if (!PyArg_ParseTuple(args, "OO|Ol:islice", &seq, &a1, &a2, &step))
if (!PyArg_UnpackTuple(args, "islice", 2, 4, &seq, &a1, &a2, &a3))
return NULL;
numargs = PyTuple_Size(args);
if (numargs == 2) {
if (a1 != Py_None) {
stop = PyInt_AsLong(a1);
@ -1059,39 +1059,41 @@ islice_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
if (PyErr_Occurred())
PyErr_Clear();
PyErr_SetString(PyExc_ValueError,
"Stop argument must be a non-negative integer or None.");
"Stop argument for islice() must be a non-negative integer or None.");
return NULL;
}
}
} else {
start = PyInt_AsLong(a1);
if (start == -1 && PyErr_Occurred()) {
if (a1 != Py_None)
start = PyInt_AsLong(a1);
if (start == -1 && PyErr_Occurred())
PyErr_Clear();
PyErr_SetString(PyExc_ValueError,
"Start argument must be a non-negative integer.");
return NULL;
}
if (a2 != Py_None) {
stop = PyInt_AsLong(a2);
if (stop == -1) {
if (PyErr_Occurred())
PyErr_Clear();
PyErr_SetString(PyExc_ValueError,
"Stop argument must be a non-negative integer or None.");
"Stop argument for islice() must be a non-negative integer or None.");
return NULL;
}
}
}
if (start<0 || stop<-1) {
PyErr_SetString(PyExc_ValueError,
"Indices for islice() must be non-negative integers.");
"Indices for islice() must be non-negative integers or None.");
return NULL;
}
if (a3 != NULL) {
if (a3 != Py_None)
step = PyInt_AsLong(a3);
if (step == -1 && PyErr_Occurred())
PyErr_Clear();
}
if (step<1) {
PyErr_SetString(PyExc_ValueError,
"Step must be one or larger for islice().");
"Step for islice() must be a positive integer or None.");
return NULL;
}