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The previous made the stop argument optional.

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It is better to be explicit and just allow stop to be None.
This commit is contained in:
Raymond Hettinger 2003-05-02 19:44:20 +00:00
parent 14ef54cd83
commit 341deb74e7
3 changed files with 10 additions and 13 deletions
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17
Doc/lib/libitertools.tex
View file

@ -197,9 +197,9 @@ by functions or loops that truncate the stream.
If \var{start} is non-zero, then elements from the iterable are skipped
until start is reached. Afterward, elements are returned consecutively
unless \var{step} is set higher than one which results in items being
skipped. If \var{stop} is not specified or is \code{None}, then iteration
continues indefinitely; otherwise, it stops at the specified position.
Unlike regular slicing,
skipped. If \var{stop} is \code{None}, then iteration continues until
the iterator is exhausted, if at all; otherwise, it stops at the specified
position. Unlike regular slicing,
\function{islice()} does not support negative values for \var{start},
\var{stop}, or \var{step}. Can be used to extract related fields
from data where the internal structure has been flattened (for
@ -208,13 +208,10 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def islice(iterable, *args):
if args:
s = slice(*args)
next = s.start or 0
stop = s.stop
step = s.step or 1
else:
next, stop, step = 0, None, 1
s = slice(*args)
next = s.start or 0
stop = s.stop
step = s.step or 1
for cnt, element in enumerate(iterable):
if cnt < next:
continue

2
Lib/test/test_itertools.py
View file

@ -78,12 +78,12 @@ class TestBasicOps(unittest.TestCase):
self.assertEqual(list(islice(xrange(100), *args)), range(*tgtargs))
# Test stop=None
self.assertEqual(list(islice(xrange(10))), range(10))
self.assertEqual(list(islice(xrange(10), 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))
# Test invalid arguments
self.assertRaises(TypeError, islice, xrange(10))
self.assertRaises(TypeError, islice, xrange(10), 1, 2, 3, 4)
self.assertRaises(ValueError, islice, xrange(10), -5, 10, 1)
self.assertRaises(ValueError, islice, xrange(10), 1, -5, -1)

4
Modules/itertoolsmodule.c
View file

@ -477,7 +477,7 @@ islice_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
isliceobject *lz;
numargs = PyTuple_Size(args);
if (!PyArg_ParseTuple(args, "O|OOl:islice", &seq, &a1, &a2, &step))
if (!PyArg_ParseTuple(args, "OO|Ol:islice", &seq, &a1, &a2, &step))
return NULL;
if (numargs == 2) {
@ -491,7 +491,7 @@ islice_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
return NULL;
}
}
} else if (numargs == 3 || numargs == 4) {
} else {
start = PyInt_AsLong(a1);
if (start == -1 && PyErr_Occurred()) {
PyErr_Clear();