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Add itertools.izip_longest().
This commit is contained in:
Raymond Hettinger
parent
15cade0568
commit
d36862cf78
4 changed files with 317 additions and 0 deletions
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@ -302,6 +302,33 @@ by functions or loops that truncate the stream.
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don't care about trailing, unmatched values from the longer iterables.
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\end{funcdesc}
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\begin{funcdesc}{izip_longest}{*iterables\optional{, fillvalue}}
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Make an iterator that aggregates elements from each of the iterables.
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If the iterables are of uneven length, missing values are filled-in
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with \var{fillvalue}. Iteration continues until the longest iterable
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is exhausted. Equivalent to:
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\begin{verbatim}
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def izip_longest(*args, **kwds):
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fillvalue = kwds.get('fillvalue')
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def sentinel(counter = ([fillvalue]*(len(args)-1)).pop):
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yield counter() # yields the fillvalue, or raises IndexError
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fillers = repeat(fillvalue)
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iters = [chain(it, sentinel(), fillers) for it in args]
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try:
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for tup in izip(*iters):
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yield tup
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except IndexError:
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pass
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\end{verbatim}
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If one of the iterables is potentially infinite, then the
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\function{izip_longest()} function should be wrapped with something
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that limits the number of calls (for example \function{islice()} or
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\function{take()}).
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\versionadded{2.6}
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\end{funcdesc}
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\begin{funcdesc}{repeat}{object\optional{, times}}
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Make an iterator that returns \var{object} over and over again.
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Runs indefinitely unless the \var{times} argument is specified.
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@ -198,6 +198,51 @@ def test_izip(self):
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ids = map(id, list(izip('abc', 'def')))
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self.assertEqual(len(dict.fromkeys(ids)), len(ids))
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def test_iziplongest(self):
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for args in [
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['abc', range(6)],
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[range(6), 'abc'],
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[range(1000), range(2000,2100), range(3000,3050)],
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[range(1000), range(0), range(3000,3050), range(1200), range(1500)],
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[range(1000), range(0), range(3000,3050), range(1200), range(1500), range(0)],
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]:
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target = map(None, *args)
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self.assertEqual(list(izip_longest(*args)), target)
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self.assertEqual(list(izip_longest(*args, **{})), target)
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target = [tuple((e is None and 'X' or e) for e in t) for t in target] # Replace None fills with 'X'
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self.assertEqual(list(izip_longest(*args, **dict(fillvalue='X'))), target)
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self.assertEqual(take(3,izip_longest('abcdef', count())), zip('abcdef', range(3))) # take 3 from infinite input
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self.assertEqual(list(izip_longest()), zip())
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self.assertEqual(list(izip_longest([])), zip([]))
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self.assertEqual(list(izip_longest('abcdef')), zip('abcdef'))
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self.assertEqual(list(izip_longest('abc', 'defg', **{})), map(None, 'abc', 'defg')) # empty keyword dict
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self.assertRaises(TypeError, izip_longest, 3)
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self.assertRaises(TypeError, izip_longest, range(3), 3)
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for stmt in [
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"izip_longest('abc', fv=1)",
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"izip_longest('abc', fillvalue=1, bogus_keyword=None)",
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]:
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try:
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eval(stmt, globals(), locals())
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except TypeError:
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pass
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else:
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self.fail('Did not raise Type in: ' + stmt)
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# Check tuple re-use (implementation detail)
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self.assertEqual([tuple(list(pair)) for pair in izip_longest('abc', 'def')],
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zip('abc', 'def'))
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self.assertEqual([pair for pair in izip_longest('abc', 'def')],
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zip('abc', 'def'))
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ids = map(id, izip_longest('abc', 'def'))
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self.assertEqual(min(ids), max(ids))
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ids = map(id, list(izip_longest('abc', 'def')))
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self.assertEqual(len(dict.fromkeys(ids)), len(ids))
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def test_repeat(self):
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self.assertEqual(zip(xrange(3),repeat('a')),
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[(0, 'a'), (1, 'a'), (2, 'a')])
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@ -611,6 +656,15 @@ def test_izip(self):
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self.assertRaises(TypeError, list, izip(N(s)))
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self.assertRaises(ZeroDivisionError, list, izip(E(s)))
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def test_iziplongest(self):
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for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
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for g in (G, I, Ig, S, L, R):
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self.assertEqual(list(izip_longest(g(s))), zip(g(s)))
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self.assertEqual(list(izip_longest(g(s), g(s))), zip(g(s), g(s)))
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self.assertRaises(TypeError, izip_longest, X(s))
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self.assertRaises(TypeError, list, izip_longest(N(s)))
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self.assertRaises(ZeroDivisionError, list, izip_longest(E(s)))
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def test_imap(self):
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for s in (range(10), range(0), range(100), (7,11), xrange(20,50,5)):
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for g in (G, I, Ig, S, L, R):
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@ -127,6 +127,8 @@ Library
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- Added heapq.merge() for merging sorted input streams.
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- Added itertools.izip_longest().
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- Have the encoding package's search function dynamically import using absolute
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import semantics.
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@ -2472,6 +2472,238 @@ static PyTypeObject repeat_type = {
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PyObject_GC_Del, /* tp_free */
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};
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/* iziplongest object ************************************************************/
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#include "Python.h"
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typedef struct {
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PyObject_HEAD
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Py_ssize_t tuplesize;
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Py_ssize_t numactive;
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PyObject *ittuple; /* tuple of iterators */
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PyObject *result;
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PyObject *fillvalue;
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PyObject *filler; /* repeat(fillvalue) */
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} iziplongestobject;
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static PyTypeObject iziplongest_type;
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static PyObject *
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izip_longest_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
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{
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iziplongestobject *lz;
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Py_ssize_t i;
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PyObject *ittuple; /* tuple of iterators */
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PyObject *result;
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PyObject *fillvalue = Py_None;
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PyObject *filler;
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Py_ssize_t tuplesize = PySequence_Length(args);
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if (kwds != NULL && PyDict_CheckExact(kwds) && PyDict_Size(kwds) > 0) {
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fillvalue = PyDict_GetItemString(kwds, "fillvalue");
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if (fillvalue == NULL || PyDict_Size(kwds) > 1) {
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PyErr_SetString(PyExc_TypeError,
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"izip_longest() got an unexpected keyword argument");
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return NULL;
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}
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}
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/* args must be a tuple */
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assert(PyTuple_Check(args));
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/* obtain iterators */
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ittuple = PyTuple_New(tuplesize);
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if (ittuple == NULL)
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return NULL;
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for (i=0; i < tuplesize; ++i) {
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PyObject *item = PyTuple_GET_ITEM(args, i);
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PyObject *it = PyObject_GetIter(item);
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if (it == NULL) {
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if (PyErr_ExceptionMatches(PyExc_TypeError))
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PyErr_Format(PyExc_TypeError,
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"izip_longest argument #%zd must support iteration",
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i+1);
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Py_DECREF(ittuple);
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return NULL;
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}
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PyTuple_SET_ITEM(ittuple, i, it);
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}
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filler = PyObject_CallFunctionObjArgs((PyObject *)(&repeat_type), fillvalue, NULL);
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if (filler == NULL) {
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Py_DECREF(ittuple);
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return NULL;
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}
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/* create a result holder */
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result = PyTuple_New(tuplesize);
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if (result == NULL) {
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Py_DECREF(ittuple);
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Py_DECREF(filler);
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return NULL;
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}
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for (i=0 ; i < tuplesize ; i++) {
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Py_INCREF(Py_None);
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PyTuple_SET_ITEM(result, i, Py_None);
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}
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/* create iziplongestobject structure */
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lz = (iziplongestobject *)type->tp_alloc(type, 0);
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if (lz == NULL) {
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Py_DECREF(ittuple);
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Py_DECREF(filler);
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Py_DECREF(result);
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return NULL;
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}
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lz->ittuple = ittuple;
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lz->tuplesize = tuplesize;
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lz->numactive = tuplesize;
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lz->result = result;
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Py_INCREF(fillvalue);
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lz->fillvalue = fillvalue;
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Py_INCREF(filler);
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lz->filler = filler; /* XXX */
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return (PyObject *)lz;
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}
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static void
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izip_longest_dealloc(iziplongestobject *lz)
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{
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PyObject_GC_UnTrack(lz);
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Py_XDECREF(lz->ittuple);
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Py_XDECREF(lz->result);
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Py_XDECREF(lz->fillvalue);
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Py_XDECREF(lz->filler);
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lz->ob_type->tp_free(lz);
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}
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static int
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izip_longest_traverse(iziplongestobject *lz, visitproc visit, void *arg)
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{
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Py_VISIT(lz->ittuple);
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Py_VISIT(lz->result);
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Py_VISIT(lz->fillvalue);
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Py_VISIT(lz->filler);
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return 0;
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}
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static PyObject *
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izip_longest_next(iziplongestobject *lz)
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{
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Py_ssize_t i;
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Py_ssize_t tuplesize = lz->tuplesize;
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PyObject *result = lz->result;
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PyObject *it;
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PyObject *item;
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PyObject *olditem;
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if (tuplesize == 0)
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return NULL;
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if (result->ob_refcnt == 1) {
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Py_INCREF(result);
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for (i=0 ; i < tuplesize ; i++) {
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it = PyTuple_GET_ITEM(lz->ittuple, i);
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assert(PyIter_Check(it));
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item = (*it->ob_type->tp_iternext)(it);
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if (item == NULL) {
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if (lz->numactive <= 1) {
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Py_DECREF(result);
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return NULL;
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} else {
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Py_INCREF(lz->filler);
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PyTuple_SET_ITEM(lz->ittuple, i, lz->filler);
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Py_INCREF(lz->fillvalue);
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item = lz->fillvalue;
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Py_DECREF(it);
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lz->numactive -= 1;
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}
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}
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olditem = PyTuple_GET_ITEM(result, i);
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PyTuple_SET_ITEM(result, i, item);
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Py_DECREF(olditem);
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}
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} else {
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result = PyTuple_New(tuplesize);
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if (result == NULL)
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return NULL;
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for (i=0 ; i < tuplesize ; i++) {
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it = PyTuple_GET_ITEM(lz->ittuple, i);
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assert(PyIter_Check(it));
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item = (*it->ob_type->tp_iternext)(it);
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if (item == NULL) {
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if (lz->numactive <= 1) {
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Py_DECREF(result);
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return NULL;
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} else {
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Py_INCREF(lz->filler);
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PyTuple_SET_ITEM(lz->ittuple, i, lz->filler);
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Py_INCREF(lz->fillvalue);
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item = lz->fillvalue;
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Py_DECREF(it);
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lz->numactive -= 1;
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}
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}
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PyTuple_SET_ITEM(result, i, item);
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}
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}
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return result;
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}
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PyDoc_STRVAR(izip_longest_doc,
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"izip_longest(iter1 [,iter2 [...]], [fillvalue=None]) --> izip_longest object\n\
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\n\
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Return an izip_longest object whose .next() method returns a tuple where\n\
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the i-th element comes from the i-th iterable argument. The .next()\n\
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method continues until the longest iterable in the argument sequence\n\
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is exhausted and then it raises StopIteration. When the shorter iterables\n\
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are exhausted, the fillvalue is substituted in their place. The fillvalue\n\
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defaults to None or can be specified by a keyword argument.\n\
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");
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static PyTypeObject iziplongest_type = {
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PyObject_HEAD_INIT(NULL)
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0, /* ob_size */
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"itertools.izip_longest", /* tp_name */
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sizeof(iziplongestobject), /* tp_basicsize */
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0, /* tp_itemsize */
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/* methods */
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(destructor)izip_longest_dealloc, /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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0, /* tp_compare */
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0, /* tp_repr */
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0, /* tp_as_number */
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0, /* tp_as_sequence */
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0, /* tp_as_mapping */
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0, /* tp_hash */
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0, /* tp_call */
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0, /* tp_str */
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PyObject_GenericGetAttr, /* tp_getattro */
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
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Py_TPFLAGS_BASETYPE, /* tp_flags */
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izip_longest_doc, /* tp_doc */
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(traverseproc)izip_longest_traverse, /* tp_traverse */
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0, /* tp_clear */
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0, /* tp_richcompare */
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0, /* tp_weaklistoffset */
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PyObject_SelfIter, /* tp_iter */
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(iternextfunc)izip_longest_next, /* tp_iternext */
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0, /* tp_methods */
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0, /* tp_members */
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0, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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0, /* tp_init */
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0, /* tp_alloc */
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izip_longest_new, /* tp_new */
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PyObject_GC_Del, /* tp_free */
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};
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/* module level code ********************************************************/
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@ -2485,6 +2717,7 @@ repeat(elem [,n]) --> elem, elem, elem, ... endlessly or up to n times\n\
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\n\
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Iterators terminating on the shortest input sequence:\n\
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izip(p, q, ...) --> (p[0], q[0]), (p[1], q[1]), ... \n\
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izip_longest(p, q, ...) --> (p[0], q[0]), (p[1], q[1]), ... \n\
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ifilter(pred, seq) --> elements of seq where pred(elem) is True\n\
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ifilterfalse(pred, seq) --> elements of seq where pred(elem) is False\n\
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islice(seq, [start,] stop [, step]) --> elements from\n\
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@ -2522,6 +2755,7 @@ inititertools(void)
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&ifilterfalse_type,
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&count_type,
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&izip_type,
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&iziplongest_type,
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&repeat_type,
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&groupby_type,
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NULL
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