SF patch #941881: PEP 309 Implementation (Partial Function Application).

Combined efforts of many including Peter Harris, Hye-Shik Chang,
Martin v. Löwis, Nick Coghlan, Paul Moore, and Raymond Hettinger.

1 files changed, 154 insertions, 0 deletions

diff --git a/Lib/test/test_functional.py b/Lib/test/test_functional.py
new file mode 100644
index 0000000..db3a289
--- /dev/null
+++ b/Lib/test/test_functional.py
@@ -0,0 +1,154 @@
+import functional
+import unittest
+from test import test_support
+
+@staticmethod
+def PythonPartial(func, *args, **keywords):
+    'Pure Python approximation of partial()'
+    def newfunc(*fargs, **fkeywords):
+        newkeywords = keywords.copy()
+        newkeywords.update(fkeywords)
+        return func(*(args + fargs), **newkeywords)
+    newfunc.func = func
+    newfunc.args = args
+    newfunc.keywords = keywords
+    return newfunc
+
+def capture(*args, **kw):
+    """capture all positional and keyword arguments"""
+    return args, kw
+
+class TestPartial(unittest.TestCase):
+
+    thetype = functional.partial
+
+    def test_basic_examples(self):
+        p = self.thetype(capture, 1, 2, a=10, b=20)
+        self.assertEqual(p(3, 4, b=30, c=40),
+                         ((1, 2, 3, 4), dict(a=10, b=30, c=40)))
+        p = self.thetype(map, lambda x: x*10)
+        self.assertEqual(p([1,2,3,4]), [10, 20, 30, 40])
+
+    def test_attributes(self):
+        p = self.thetype(capture, 1, 2, a=10, b=20)
+        # attributes should be readable
+        self.assertEqual(p.func, capture)
+        self.assertEqual(p.args, (1, 2))
+        self.assertEqual(p.keywords, dict(a=10, b=20))
+        # attributes should not be writable
+        if not isinstance(self.thetype, type):
+            return
+        self.assertRaises(TypeError, setattr, p, 'func', map)
+        self.assertRaises(TypeError, setattr, p, 'args', (1, 2))
+        self.assertRaises(TypeError, setattr, p, 'keywords', dict(a=1, b=2))
+
+    def test_argument_checking(self):
+        self.assertRaises(TypeError, self.thetype)     # need at least a func arg
+        try:
+            self.thetype(2)()
+        except TypeError:
+            pass
+        else:
+            self.fail('First arg not checked for callability')
+
+    def test_protection_of_callers_dict_argument(self):
+        # a caller's dictionary should not be altered by partial
+        def func(a=10, b=20):
+            return a
+        d = {'a':3}
+        p = self.thetype(func, a=5)
+        self.assertEqual(p(**d), 3)
+        self.assertEqual(d, {'a':3})
+        p(b=7)
+        self.assertEqual(d, {'a':3})
+
+    def test_arg_combinations(self):
+        # exercise special code paths for zero args in either partial
+        # object or the caller
+        p = self.thetype(capture)
+        self.assertEqual(p(), ((), {}))
+        self.assertEqual(p(1,2), ((1,2), {}))
+        p = self.thetype(capture, 1, 2)
+        self.assertEqual(p(), ((1,2), {}))
+        self.assertEqual(p(3,4), ((1,2,3,4), {}))
+
+    def test_kw_combinations(self):
+        # exercise special code paths for no keyword args in
+        # either the partial object or the caller
+        p = self.thetype(capture)
+        self.assertEqual(p(), ((), {}))
+        self.assertEqual(p(a=1), ((), {'a':1}))
+        p = self.thetype(capture, a=1)
+        self.assertEqual(p(), ((), {'a':1}))
+        self.assertEqual(p(b=2), ((), {'a':1, 'b':2}))
+        # keyword args in the call override those in the partial object
+        self.assertEqual(p(a=3, b=2), ((), {'a':3, 'b':2}))
+
+    def test_positional(self):
+        # make sure positional arguments are captured correctly
+        for args in [(), (0,), (0,1), (0,1,2), (0,1,2,3)]:
+            p = self.thetype(capture, *args)
+            expected = args + ('x',)
+            got, empty = p('x')
+            self.failUnless(expected == got and empty == {})
+
+    def test_keyword(self):
+        # make sure keyword arguments are captured correctly
+        for a in ['a', 0, None, 3.5]:
+            p = self.thetype(capture, a=a)
+            expected = {'a':a,'x':None}
+            empty, got = p(x=None)
+            self.failUnless(expected == got and empty == ())
+
+    def test_no_side_effects(self):
+        # make sure there are no side effects that affect subsequent calls
+        p = self.thetype(capture, 0, a=1)
+        args1, kw1 = p(1, b=2)
+        self.failUnless(args1 == (0,1) and kw1 == {'a':1,'b':2})
+        args2, kw2 = p()
+        self.failUnless(args2 == (0,) and kw2 == {'a':1})
+
+    def test_error_propagation(self):
+        def f(x, y):
+            x / y
+        self.assertRaises(ZeroDivisionError, self.thetype(f, 1, 0))
+        self.assertRaises(ZeroDivisionError, self.thetype(f, 1), 0)
+        self.assertRaises(ZeroDivisionError, self.thetype(f), 1, 0)
+        self.assertRaises(ZeroDivisionError, self.thetype(f, y=0), 1)
+
+
+class PartialSubclass(functional.partial):
+    pass
+
+class TestPartialSubclass(TestPartial):
+
+    thetype = PartialSubclass
+
+
+class TestPythonPartial(TestPartial):
+
+    thetype = PythonPartial
+
+
+
+def test_main(verbose=None):
+    import sys
+    test_classes = (
+        TestPartial,
+        TestPartialSubclass,
+        TestPythonPartial,
+    )
+    test_support.run_unittest(*test_classes)
+
+    # verify reference counting
+    if verbose and hasattr(sys, "gettotalrefcount"):
+        import gc
+        counts = [None] * 5
+        for i in xrange(len(counts)):
+            test_support.run_unittest(*test_classes)
+            gc.collect()
+            counts[i] = sys.gettotalrefcount()
+        print counts
+
+if __name__ == '__main__':
+    test_main(verbose=True)