Modified itertools.izip() to match the behavior of __builtin__.zip()

which can now take zero arguments.

diff --git a/Doc/lib/libitertools.tex b/Doc/lib/libitertools.tex
index b708050190dbd4eddb6ef32f95e85af989a20f85..cd7e6de8fa11f7e413ba5827166329b02040e792 100644 (file)
--- a/Doc/lib/libitertools.tex
+++ b/Doc/lib/libitertools.tex
@@ -226,10 +226,13 @@ by functions or loops that truncate the stream.
   \begin{verbatim}
      def izip(*iterables):
          iterables = map(iter, iterables)
-         while True:
+         while iterables:
              result = [i.next() for i in iterables]
              yield tuple(result)
   \end{verbatim}
+
+  \versionchanged[When no iterables are specified, returns a zero length
+                  iterator instead of raising a TypeError exception]{2.4}  
 \end{funcdesc}
 
 \begin{funcdesc}{repeat}{object\optional{, times}}

diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index 52ae110ba4d61dbaa1899cb9484818b327a6b73f..f96ccd5d48e5c754f18d88f8812739f0e4b09b57 100644 (file)
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -87,7 +87,7 @@ class TestBasicOps(unittest.TestCase):
         self.assertEqual(list(izip('abcdef', range(3))), zip('abcdef', range(3)))
         self.assertEqual(take(3,izip('abcdef', count())), zip('abcdef', range(3)))
         self.assertEqual(list(izip('abcdef')), zip('abcdef'))
-        self.assertRaises(TypeError, izip)
+        self.assertEqual(list(izip()), zip())
         self.assertRaises(TypeError, izip, 3)
         self.assertRaises(TypeError, izip, range(3), 3)
         # Check tuple re-use (implementation detail)
@@ -199,6 +199,8 @@ class TestBasicOps(unittest.TestCase):
         self.assertRaises(ValueError, dropwhile(errfunc, [(4,5)]).next)
 
     def test_StopIteration(self):
+        self.assertRaises(StopIteration, izip().next)
+
         for f in (chain, cycle, izip):
             self.assertRaises(StopIteration, f([]).next)
             self.assertRaises(StopIteration, f(StopNow()).next)
@@ -540,6 +542,9 @@ True
 >>> no(lambda x: x%2==0, [1, 2, 5, 9])
 False
 
+>>> quantify(lambda x: x%2==0, xrange(99))
+50
+
 >>> list(window('abc'))
 [('a', 'b'), ('b', 'c')]
 

diff --git a/Misc/NEWS b/Misc/NEWS
index 34786bfaca2cf20642f17541b0b7dbae1152f919..410391cd135cd306f4d12a63c725056c9af521bb 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -23,6 +23,9 @@ Extension modules
 Library
 -------
 
+- itertools.izip() with no arguments now returns an empty iterator instead
+  of raising a TypeError exception.
+
 - _strptime.py now has a behind-the-scenes caching mechanism for the most
   recent TimeRE instance used along with the last five unique directive
   patterns.  The overall module was also made more thread-safe.

diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index e63d02a4c943ddb21ea87ae9e4812f1656e2d8b1..4a99fcebec640928322cd66c0404940f8fc4c8ca 100644 (file)
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -1510,12 +1510,6 @@ izip_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
        PyObject *result;
        int tuplesize = PySequence_Length(args);
 
-       if (tuplesize < 1) {
-               PyErr_SetString(PyExc_TypeError,
-                               "izip() requires at least one sequence");
-               return NULL;
-       }
-
        /* args must be a tuple */
        assert(PyTuple_Check(args));
 
@@ -1598,6 +1592,8 @@ izip_next(izipobject *lz)
        PyObject *it;
        PyObject *item;
 
+       if (tuplesize == 0)
+               return NULL;
        if (result->ob_refcnt == 1) {
                for (i=0 ; i < tuplesize ; i++) {
                        it = PyTuple_GET_ITEM(lz->ittuple, i);