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Make starmap() match its pure python definition and accept any itertable input (not just tuples).

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Raymond Hettinger 2008-01-17 03:02:14 +00:00
parent 3ad2acc857
commit 473170908e
4 changed files with 15 additions and 8 deletions
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10
Doc/library/itertools.rst
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@ -330,17 +330,19 @@ loops that truncate the stream.
.. function:: starmap(function, iterable) .. function:: starmap(function, iterable)
Make an iterator that computes the function using arguments tuples obtained from Make an iterator that computes the function using arguments obtained from
the iterable. Used instead of :func:`imap` when argument parameters are already the iterable. Used instead of :func:`imap` when argument parameters are already
grouped in tuples from a single iterable (the data has been "pre-zipped"). The grouped in tuples from a single iterable (the data has been "pre-zipped"). The
difference between :func:`imap` and :func:`starmap` parallels the distinction difference between :func:`imap` and :func:`starmap` parallels the distinction
between ``function(a,b)`` and ``function(*c)``. Equivalent to:: between ``function(a,b)`` and ``function(*c)``. Equivalent to::
def starmap(function, iterable): def starmap(function, iterable):
iterable = iter(iterable) for args in iterable:
while True: yield function(*args)
yield function(*iterable.next())
.. versionchanged:: 2.6
Previously, :func:`starmap` required the function arguments to be tuples.
Now, any iterable is allowed.
.. function:: takewhile(predicate, iterable) .. function:: takewhile(predicate, iterable)

3
Lib/test/test_itertools.py
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@ -292,7 +292,8 @@ class TestBasicOps(unittest.TestCase):
self.assertEqual(take(3, starmap(operator.pow, izip(count(), count(1)))), self.assertEqual(take(3, starmap(operator.pow, izip(count(), count(1)))),
[0**1, 1**2, 2**3]) [0**1, 1**2, 2**3])
self.assertEqual(list(starmap(operator.pow, [])), []) self.assertEqual(list(starmap(operator.pow, [])), [])
self.assertRaises(TypeError, list, starmap(operator.pow, [[4,5]])) self.assertEqual(list(starmap(operator.pow, [iter([4,5])])), [4**5])
self.assertRaises(TypeError, list, starmap(operator.pow, [None]))
self.assertRaises(TypeError, starmap) self.assertRaises(TypeError, starmap)
self.assertRaises(TypeError, starmap, operator.pow, [(4,5)], 'extra') self.assertRaises(TypeError, starmap, operator.pow, [(4,5)], 'extra')
self.assertRaises(TypeError, starmap(10, [(4,5)]).next) self.assertRaises(TypeError, starmap(10, [(4,5)]).next)

3
Misc/NEWS
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@ -993,6 +993,9 @@ Extension Modules
the context manager protocol. The _winreg module also gained a new function the context manager protocol. The _winreg module also gained a new function
``ExpandEnvironmentStrings`` to expand REG_EXPAND_SZ keys. ``ExpandEnvironmentStrings`` to expand REG_EXPAND_SZ keys.
- itertools.starmap() now accepts any iterable input. Previously, it required
the function inputs to be tuples.
- Issue #1646: Make socket support TIPC. The socket module now has support - Issue #1646: Make socket support TIPC. The socket module now has support
for TIPC under Linux, see http://tipc.sf.net/ for more information. for TIPC under Linux, see http://tipc.sf.net/ for more information.

5
Modules/itertoolsmodule.c
View file

@ -1356,10 +1356,11 @@ starmap_next(starmapobject *lz)
if (args == NULL) if (args == NULL)
return NULL; return NULL;
if (!PyTuple_CheckExact(args)) { if (!PyTuple_CheckExact(args)) {
PyObject *newargs = PySequence_Tuple(args);
Py_DECREF(args); Py_DECREF(args);
PyErr_SetString(PyExc_TypeError, if (newargs == NULL)
"iterator must return a tuple");
return NULL; return NULL;
args = newargs;
} }
result = PyObject_Call(lz->func, args, NULL); result = PyObject_Call(lz->func, args, NULL);
Py_DECREF(args); Py_DECREF(args);