Python code coverage for Lib/test/test_scope.py

#	count	content
1	n/a	import unittest
2	n/a	import weakref
3	n/a
4	n/a	from test.support import check_syntax_error, cpython_only
5	n/a
6	n/a
7	n/a	class ScopeTests(unittest.TestCase):
8	n/a
9	n/a	def testSimpleNesting(self):
10	n/a
11	n/a	def make_adder(x):
12	n/a	def adder(y):
13	n/a	return x + y
14	n/a	return adder
15	n/a
16	n/a	inc = make_adder(1)
17	n/a	plus10 = make_adder(10)
18	n/a
19	n/a	self.assertEqual(inc(1), 2)
20	n/a	self.assertEqual(plus10(-2), 8)
21	n/a
22	n/a	def testExtraNesting(self):
23	n/a
24	n/a	def make_adder2(x):
25	n/a	def extra(): # check freevars passing through non-use scopes
26	n/a	def adder(y):
27	n/a	return x + y
28	n/a	return adder
29	n/a	return extra()
30	n/a
31	n/a	inc = make_adder2(1)
32	n/a	plus10 = make_adder2(10)
33	n/a
34	n/a	self.assertEqual(inc(1), 2)
35	n/a	self.assertEqual(plus10(-2), 8)
36	n/a
37	n/a	def testSimpleAndRebinding(self):
38	n/a
39	n/a	def make_adder3(x):
40	n/a	def adder(y):
41	n/a	return x + y
42	n/a	x = x + 1 # check tracking of assignment to x in defining scope
43	n/a	return adder
44	n/a
45	n/a	inc = make_adder3(0)
46	n/a	plus10 = make_adder3(9)
47	n/a
48	n/a	self.assertEqual(inc(1), 2)
49	n/a	self.assertEqual(plus10(-2), 8)
50	n/a
51	n/a	def testNestingGlobalNoFree(self):
52	n/a
53	n/a	def make_adder4(): # XXX add exta level of indirection
54	n/a	def nest():
55	n/a	def nest():
56	n/a	def adder(y):
57	n/a	return global_x + y # check that plain old globals work
58	n/a	return adder
59	n/a	return nest()
60	n/a	return nest()
61	n/a
62	n/a	global_x = 1
63	n/a	adder = make_adder4()
64	n/a	self.assertEqual(adder(1), 2)
65	n/a
66	n/a	global_x = 10
67	n/a	self.assertEqual(adder(-2), 8)
68	n/a
69	n/a	def testNestingThroughClass(self):
70	n/a
71	n/a	def make_adder5(x):
72	n/a	class Adder:
73	n/a	def __call__(self, y):
74	n/a	return x + y
75	n/a	return Adder()
76	n/a
77	n/a	inc = make_adder5(1)
78	n/a	plus10 = make_adder5(10)
79	n/a
80	n/a	self.assertEqual(inc(1), 2)
81	n/a	self.assertEqual(plus10(-2), 8)
82	n/a
83	n/a	def testNestingPlusFreeRefToGlobal(self):
84	n/a
85	n/a	def make_adder6(x):
86	n/a	global global_nest_x
87	n/a	def adder(y):
88	n/a	return global_nest_x + y
89	n/a	global_nest_x = x
90	n/a	return adder
91	n/a
92	n/a	inc = make_adder6(1)
93	n/a	plus10 = make_adder6(10)
94	n/a
95	n/a	self.assertEqual(inc(1), 11) # there's only one global
96	n/a	self.assertEqual(plus10(-2), 8)
97	n/a
98	n/a	def testNearestEnclosingScope(self):
99	n/a
100	n/a	def f(x):
101	n/a	def g(y):
102	n/a	x = 42 # check that this masks binding in f()
103	n/a	def h(z):
104	n/a	return x + z
105	n/a	return h
106	n/a	return g(2)
107	n/a
108	n/a	test_func = f(10)
109	n/a	self.assertEqual(test_func(5), 47)
110	n/a
111	n/a	def testMixedFreevarsAndCellvars(self):
112	n/a
113	n/a	def identity(x):
114	n/a	return x
115	n/a
116	n/a	def f(x, y, z):
117	n/a	def g(a, b, c):
118	n/a	a = a + x # 3
119	n/a	def h():
120	n/a	# z * (4 + 9)
121	n/a	# 3 * 13
122	n/a	return identity(z * (b + y))
123	n/a	y = c + z # 9
124	n/a	return h
125	n/a	return g
126	n/a
127	n/a	g = f(1, 2, 3)
128	n/a	h = g(2, 4, 6)
129	n/a	self.assertEqual(h(), 39)
130	n/a
131	n/a	def testFreeVarInMethod(self):
132	n/a
133	n/a	def test():
134	n/a	method_and_var = "var"
135	n/a	class Test:
136	n/a	def method_and_var(self):
137	n/a	return "method"
138	n/a	def test(self):
139	n/a	return method_and_var
140	n/a	def actual_global(self):
141	n/a	return str("global")
142	n/a	def str(self):
143	n/a	return str(self)
144	n/a	return Test()
145	n/a
146	n/a	t = test()
147	n/a	self.assertEqual(t.test(), "var")
148	n/a	self.assertEqual(t.method_and_var(), "method")
149	n/a	self.assertEqual(t.actual_global(), "global")
150	n/a
151	n/a	method_and_var = "var"
152	n/a	class Test:
153	n/a	# this class is not nested, so the rules are different
154	n/a	def method_and_var(self):
155	n/a	return "method"
156	n/a	def test(self):
157	n/a	return method_and_var
158	n/a	def actual_global(self):
159	n/a	return str("global")
160	n/a	def str(self):
161	n/a	return str(self)
162	n/a
163	n/a	t = Test()
164	n/a	self.assertEqual(t.test(), "var")
165	n/a	self.assertEqual(t.method_and_var(), "method")
166	n/a	self.assertEqual(t.actual_global(), "global")
167	n/a
168	n/a	def testCellIsKwonlyArg(self):
169	n/a	# Issue 1409: Initialisation of a cell value,
170	n/a	# when it comes from a keyword-only parameter
171	n/a	def foo(*, a=17):
172	n/a	def bar():
173	n/a	return a + 5
174	n/a	return bar() + 3
175	n/a
176	n/a	self.assertEqual(foo(a=42), 50)
177	n/a	self.assertEqual(foo(), 25)
178	n/a
179	n/a	def testRecursion(self):
180	n/a
181	n/a	def f(x):
182	n/a	def fact(n):
183	n/a	if n == 0:
184	n/a	return 1
185	n/a	else:
186	n/a	return n * fact(n - 1)
187	n/a	if x >= 0:
188	n/a	return fact(x)
189	n/a	else:
190	n/a	raise ValueError("x must be >= 0")
191	n/a
192	n/a	self.assertEqual(f(6), 720)
193	n/a
194	n/a
195	n/a	def testUnoptimizedNamespaces(self):
196	n/a
197	n/a	check_syntax_error(self, """if 1:
198	n/a	def unoptimized_clash1(strip):
199	n/a	def f(s):
200	n/a	from sys import *
201	n/a	return getrefcount(s) # ambiguity: free or local
202	n/a	return f
203	n/a	""")
204	n/a
205	n/a	check_syntax_error(self, """if 1:
206	n/a	def unoptimized_clash2():
207	n/a	from sys import *
208	n/a	def f(s):
209	n/a	return getrefcount(s) # ambiguity: global or local
210	n/a	return f
211	n/a	""")
212	n/a
213	n/a	check_syntax_error(self, """if 1:
214	n/a	def unoptimized_clash2():
215	n/a	from sys import *
216	n/a	def g():
217	n/a	def f(s):
218	n/a	return getrefcount(s) # ambiguity: global or local
219	n/a	return f
220	n/a	""")
221	n/a
222	n/a	check_syntax_error(self, """if 1:
223	n/a	def f():
224	n/a	def g():
225	n/a	from sys import *
226	n/a	return getrefcount # global or local?
227	n/a	""")
228	n/a
229	n/a	def testLambdas(self):
230	n/a
231	n/a	f1 = lambda x: lambda y: x + y
232	n/a	inc = f1(1)
233	n/a	plus10 = f1(10)
234	n/a	self.assertEqual(inc(1), 2)
235	n/a	self.assertEqual(plus10(5), 15)
236	n/a
237	n/a	f2 = lambda x: (lambda : lambda y: x + y)()
238	n/a	inc = f2(1)
239	n/a	plus10 = f2(10)
240	n/a	self.assertEqual(inc(1), 2)
241	n/a	self.assertEqual(plus10(5), 15)
242	n/a
243	n/a	f3 = lambda x: lambda y: global_x + y
244	n/a	global_x = 1
245	n/a	inc = f3(None)
246	n/a	self.assertEqual(inc(2), 3)
247	n/a
248	n/a	f8 = lambda x, y, z: lambda a, b, c: lambda : z * (b + y)
249	n/a	g = f8(1, 2, 3)
250	n/a	h = g(2, 4, 6)
251	n/a	self.assertEqual(h(), 18)
252	n/a
253	n/a	def testUnboundLocal(self):
254	n/a
255	n/a	def errorInOuter():
256	n/a	print(y)
257	n/a	def inner():
258	n/a	return y
259	n/a	y = 1
260	n/a
261	n/a	def errorInInner():
262	n/a	def inner():
263	n/a	return y
264	n/a	inner()
265	n/a	y = 1
266	n/a
267	n/a	self.assertRaises(UnboundLocalError, errorInOuter)
268	n/a	self.assertRaises(NameError, errorInInner)
269	n/a
270	n/a	def testUnboundLocal_AfterDel(self):
271	n/a	# #4617: It is now legal to delete a cell variable.
272	n/a	# The following functions must obviously compile,
273	n/a	# and give the correct error when accessing the deleted name.
274	n/a	def errorInOuter():
275	n/a	y = 1
276	n/a	del y
277	n/a	print(y)
278	n/a	def inner():
279	n/a	return y
280	n/a
281	n/a	def errorInInner():
282	n/a	def inner():
283	n/a	return y
284	n/a	y = 1
285	n/a	del y
286	n/a	inner()
287	n/a
288	n/a	self.assertRaises(UnboundLocalError, errorInOuter)
289	n/a	self.assertRaises(NameError, errorInInner)
290	n/a
291	n/a	def testUnboundLocal_AugAssign(self):
292	n/a	# test for bug #1501934: incorrect LOAD/STORE_GLOBAL generation
293	n/a	exec("""if 1:
294	n/a	global_x = 1
295	n/a	def f():
296	n/a	global_x += 1
297	n/a	try:
298	n/a	f()
299	n/a	except UnboundLocalError:
300	n/a	pass
301	n/a	else:
302	n/a	fail('scope of global_x not correctly determined')
303	n/a	""", {'fail': self.fail})
304	n/a
305	n/a	def testComplexDefinitions(self):
306	n/a
307	n/a	def makeReturner(*lst):
308	n/a	def returner():
309	n/a	return lst
310	n/a	return returner
311	n/a
312	n/a	self.assertEqual(makeReturner(1,2,3)(), (1,2,3))
313	n/a
314	n/a	def makeReturner2(**kwargs):
315	n/a	def returner():
316	n/a	return kwargs
317	n/a	return returner
318	n/a
319	n/a	self.assertEqual(makeReturner2(a=11)()['a'], 11)
320	n/a
321	n/a	def testScopeOfGlobalStmt(self):
322	n/a	# Examples posted by Samuele Pedroni to python-dev on 3/1/2001
323	n/a
324	n/a	exec("""if 1:
325	n/a	# I
326	n/a	x = 7
327	n/a	def f():
328	n/a	x = 1
329	n/a	def g():
330	n/a	global x
331	n/a	def i():
332	n/a	def h():
333	n/a	return x
334	n/a	return h()
335	n/a	return i()
336	n/a	return g()
337	n/a	self.assertEqual(f(), 7)
338	n/a	self.assertEqual(x, 7)
339	n/a
340	n/a	# II
341	n/a	x = 7
342	n/a	def f():
343	n/a	x = 1
344	n/a	def g():
345	n/a	x = 2
346	n/a	def i():
347	n/a	def h():
348	n/a	return x
349	n/a	return h()
350	n/a	return i()
351	n/a	return g()
352	n/a	self.assertEqual(f(), 2)
353	n/a	self.assertEqual(x, 7)
354	n/a
355	n/a	# III
356	n/a	x = 7
357	n/a	def f():
358	n/a	x = 1
359	n/a	def g():
360	n/a	global x
361	n/a	x = 2
362	n/a	def i():
363	n/a	def h():
364	n/a	return x
365	n/a	return h()
366	n/a	return i()
367	n/a	return g()
368	n/a	self.assertEqual(f(), 2)
369	n/a	self.assertEqual(x, 2)
370	n/a
371	n/a	# IV
372	n/a	x = 7
373	n/a	def f():
374	n/a	x = 3
375	n/a	def g():
376	n/a	global x
377	n/a	x = 2
378	n/a	def i():
379	n/a	def h():
380	n/a	return x
381	n/a	return h()
382	n/a	return i()
383	n/a	return g()
384	n/a	self.assertEqual(f(), 2)
385	n/a	self.assertEqual(x, 2)
386	n/a
387	n/a	# XXX what about global statements in class blocks?
388	n/a	# do they affect methods?
389	n/a
390	n/a	x = 12
391	n/a	class Global:
392	n/a	global x
393	n/a	x = 13
394	n/a	def set(self, val):
395	n/a	x = val
396	n/a	def get(self):
397	n/a	return x
398	n/a
399	n/a	g = Global()
400	n/a	self.assertEqual(g.get(), 13)
401	n/a	g.set(15)
402	n/a	self.assertEqual(g.get(), 13)
403	n/a	""")
404	n/a
405	n/a	def testLeaks(self):
406	n/a
407	n/a	class Foo:
408	n/a	count = 0
409	n/a
410	n/a	def __init__(self):
411	n/a	Foo.count += 1
412	n/a
413	n/a	def __del__(self):
414	n/a	Foo.count -= 1
415	n/a
416	n/a	def f1():
417	n/a	x = Foo()
418	n/a	def f2():
419	n/a	return x
420	n/a	f2()
421	n/a
422	n/a	for i in range(100):
423	n/a	f1()
424	n/a
425	n/a	self.assertEqual(Foo.count, 0)
426	n/a
427	n/a	def testClassAndGlobal(self):
428	n/a
429	n/a	exec("""if 1:
430	n/a	def test(x):
431	n/a	class Foo:
432	n/a	global x
433	n/a	def __call__(self, y):
434	n/a	return x + y
435	n/a	return Foo()
436	n/a
437	n/a	x = 0
438	n/a	self.assertEqual(test(6)(2), 8)
439	n/a	x = -1
440	n/a	self.assertEqual(test(3)(2), 5)
441	n/a
442	n/a	looked_up_by_load_name = False
443	n/a	class X:
444	n/a	# Implicit globals inside classes are be looked up by LOAD_NAME, not
445	n/a	# LOAD_GLOBAL.
446	n/a	locals()['looked_up_by_load_name'] = True
447	n/a	passed = looked_up_by_load_name
448	n/a
449	n/a	self.assertTrue(X.passed)
450	n/a	""")
451	n/a
452	n/a	def testLocalsFunction(self):
453	n/a
454	n/a	def f(x):
455	n/a	def g(y):
456	n/a	def h(z):
457	n/a	return y + z
458	n/a	w = x + y
459	n/a	y += 3
460	n/a	return locals()
461	n/a	return g
462	n/a
463	n/a	d = f(2)(4)
464	n/a	self.assertIn('h', d)
465	n/a	del d['h']
466	n/a	self.assertEqual(d, {'x': 2, 'y': 7, 'w': 6})
467	n/a
468	n/a	def testLocalsClass(self):
469	n/a	# This test verifies that calling locals() does not pollute
470	n/a	# the local namespace of the class with free variables. Old
471	n/a	# versions of Python had a bug, where a free variable being
472	n/a	# passed through a class namespace would be inserted into
473	n/a	# locals() by locals() or exec or a trace function.
474	n/a	#
475	n/a	# The real bug lies in frame code that copies variables
476	n/a	# between fast locals and the locals dict, e.g. when executing
477	n/a	# a trace function.
478	n/a
479	n/a	def f(x):
480	n/a	class C:
481	n/a	x = 12
482	n/a	def m(self):
483	n/a	return x
484	n/a	locals()
485	n/a	return C
486	n/a
487	n/a	self.assertEqual(f(1).x, 12)
488	n/a
489	n/a	def f(x):
490	n/a	class C:
491	n/a	y = x
492	n/a	def m(self):
493	n/a	return x
494	n/a	z = list(locals())
495	n/a	return C
496	n/a
497	n/a	varnames = f(1).z
498	n/a	self.assertNotIn("x", varnames)
499	n/a	self.assertIn("y", varnames)
500	n/a
501	n/a	@cpython_only
502	n/a	def testLocalsClass_WithTrace(self):
503	n/a	# Issue23728: after the trace function returns, the locals()
504	n/a	# dictionary is used to update all variables, this used to
505	n/a	# include free variables. But in class statements, free
506	n/a	# variables are not inserted...
507	n/a	import sys
508	n/a	self.addCleanup(sys.settrace, sys.gettrace())
509	n/a	sys.settrace(lambda a,b,c:None)
510	n/a	x = 12
511	n/a
512	n/a	class C:
513	n/a	def f(self):
514	n/a	return x
515	n/a
516	n/a	self.assertEqual(x, 12) # Used to raise UnboundLocalError
517	n/a
518	n/a	def testBoundAndFree(self):
519	n/a	# var is bound and free in class
520	n/a
521	n/a	def f(x):
522	n/a	class C:
523	n/a	def m(self):
524	n/a	return x
525	n/a	a = x
526	n/a	return C
527	n/a
528	n/a	inst = f(3)()
529	n/a	self.assertEqual(inst.a, inst.m())
530	n/a
531	n/a	@cpython_only
532	n/a	def testInteractionWithTraceFunc(self):
533	n/a
534	n/a	import sys
535	n/a	def tracer(a,b,c):
536	n/a	return tracer
537	n/a
538	n/a	def adaptgetter(name, klass, getter):
539	n/a	kind, des = getter
540	n/a	if kind == 1: # AV happens when stepping from this line to next
541	n/a	if des == "":
542	n/a	des = "_%s__%s" % (klass.__name__, name)
543	n/a	return lambda obj: getattr(obj, des)
544	n/a
545	n/a	class TestClass:
546	n/a	pass
547	n/a
548	n/a	self.addCleanup(sys.settrace, sys.gettrace())
549	n/a	sys.settrace(tracer)
550	n/a	adaptgetter("foo", TestClass, (1, ""))
551	n/a	sys.settrace(None)
552	n/a
553	n/a	self.assertRaises(TypeError, sys.settrace)
554	n/a
555	n/a	def testEvalExecFreeVars(self):
556	n/a
557	n/a	def f(x):
558	n/a	return lambda: x + 1
559	n/a
560	n/a	g = f(3)
561	n/a	self.assertRaises(TypeError, eval, g.__code__)
562	n/a
563	n/a	try:
564	n/a	exec(g.__code__, {})
565	n/a	except TypeError:
566	n/a	pass
567	n/a	else:
568	n/a	self.fail("exec should have failed, because code contained free vars")
569	n/a
570	n/a	def testListCompLocalVars(self):
571	n/a
572	n/a	try:
573	n/a	print(bad)
574	n/a	except NameError:
575	n/a	pass
576	n/a	else:
577	n/a	print("bad should not be defined")
578	n/a
579	n/a	def x():
580	n/a	[bad for s in 'a b' for bad in s.split()]
581	n/a
582	n/a	x()
583	n/a	try:
584	n/a	print(bad)
585	n/a	except NameError:
586	n/a	pass
587	n/a
588	n/a	def testEvalFreeVars(self):
589	n/a
590	n/a	def f(x):
591	n/a	def g():
592	n/a	x
593	n/a	eval("x + 1")
594	n/a	return g
595	n/a
596	n/a	f(4)()
597	n/a
598	n/a	def testFreeingCell(self):
599	n/a	# Test what happens when a finalizer accesses
600	n/a	# the cell where the object was stored.
601	n/a	class Special:
602	n/a	def __del__(self):
603	n/a	nestedcell_get()
604	n/a
605	n/a	def testNonLocalFunction(self):
606	n/a
607	n/a	def f(x):
608	n/a	def inc():
609	n/a	nonlocal x
610	n/a	x += 1
611	n/a	return x
612	n/a	def dec():
613	n/a	nonlocal x
614	n/a	x -= 1
615	n/a	return x
616	n/a	return inc, dec
617	n/a
618	n/a	inc, dec = f(0)
619	n/a	self.assertEqual(inc(), 1)
620	n/a	self.assertEqual(inc(), 2)
621	n/a	self.assertEqual(dec(), 1)
622	n/a	self.assertEqual(dec(), 0)
623	n/a
624	n/a	def testNonLocalMethod(self):
625	n/a	def f(x):
626	n/a	class c:
627	n/a	def inc(self):
628	n/a	nonlocal x
629	n/a	x += 1
630	n/a	return x
631	n/a	def dec(self):
632	n/a	nonlocal x
633	n/a	x -= 1
634	n/a	return x
635	n/a	return c()
636	n/a	c = f(0)
637	n/a	self.assertEqual(c.inc(), 1)
638	n/a	self.assertEqual(c.inc(), 2)
639	n/a	self.assertEqual(c.dec(), 1)
640	n/a	self.assertEqual(c.dec(), 0)
641	n/a
642	n/a	def testGlobalInParallelNestedFunctions(self):
643	n/a	# A symbol table bug leaked the global statement from one
644	n/a	# function to other nested functions in the same block.
645	n/a	# This test verifies that a global statement in the first
646	n/a	# function does not affect the second function.
647	n/a	local_ns = {}
648	n/a	global_ns = {}
649	n/a	exec("""if 1:
650	n/a	def f():
651	n/a	y = 1
652	n/a	def g():
653	n/a	global y
654	n/a	return y
655	n/a	def h():
656	n/a	return y + 1
657	n/a	return g, h
658	n/a	y = 9
659	n/a	g, h = f()
660	n/a	result9 = g()
661	n/a	result2 = h()
662	n/a	""", local_ns, global_ns)
663	n/a	self.assertEqual(2, global_ns["result2"])
664	n/a	self.assertEqual(9, global_ns["result9"])
665	n/a
666	n/a	def testNonLocalClass(self):
667	n/a
668	n/a	def f(x):
669	n/a	class c:
670	n/a	nonlocal x
671	n/a	x += 1
672	n/a	def get(self):
673	n/a	return x
674	n/a	return c()
675	n/a
676	n/a	c = f(0)
677	n/a	self.assertEqual(c.get(), 1)
678	n/a	self.assertNotIn("x", c.__class__.__dict__)
679	n/a
680	n/a
681	n/a	def testNonLocalGenerator(self):
682	n/a
683	n/a	def f(x):
684	n/a	def g(y):
685	n/a	nonlocal x
686	n/a	for i in range(y):
687	n/a	x += 1
688	n/a	yield x
689	n/a	return g
690	n/a
691	n/a	g = f(0)
692	n/a	self.assertEqual(list(g(5)), [1, 2, 3, 4, 5])
693	n/a
694	n/a	def testNestedNonLocal(self):
695	n/a
696	n/a	def f(x):
697	n/a	def g():
698	n/a	nonlocal x
699	n/a	x -= 2
700	n/a	def h():
701	n/a	nonlocal x
702	n/a	x += 4
703	n/a	return x
704	n/a	return h
705	n/a	return g
706	n/a
707	n/a	g = f(1)
708	n/a	h = g()
709	n/a	self.assertEqual(h(), 3)
710	n/a
711	n/a	def testTopIsNotSignificant(self):
712	n/a	# See #9997.
713	n/a	def top(a):
714	n/a	pass
715	n/a	def b():
716	n/a	global a
717	n/a
718	n/a	def testClassNamespaceOverridesClosure(self):
719	n/a	# See #17853.
720	n/a	x = 42
721	n/a	class X:
722	n/a	locals()["x"] = 43
723	n/a	y = x
724	n/a	self.assertEqual(X.y, 43)
725	n/a	class X:
726	n/a	locals()["x"] = 43
727	n/a	del x
728	n/a	self.assertFalse(hasattr(X, "x"))
729	n/a	self.assertEqual(x, 42)
730	n/a
731	n/a	@cpython_only
732	n/a	def testCellLeak(self):
733	n/a	# Issue 17927.
734	n/a	#
735	n/a	# The issue was that if self was part of a cycle involving the
736	n/a	# frame of a method call, and the method contained a nested
737	n/a	# function referencing self, thereby forcing 'self' into a
738	n/a	# cell, setting self to None would not be enough to break the
739	n/a	# frame -- the frame had another reference to the instance,
740	n/a	# which could not be cleared by the code running in the frame
741	n/a	# (though it will be cleared when the frame is collected).
742	n/a	# Without the lambda, setting self to None is enough to break
743	n/a	# the cycle.
744	n/a	class Tester:
745	n/a	def dig(self):
746	n/a	if 0:
747	n/a	lambda: self
748	n/a	try:
749	n/a	1/0
750	n/a	except Exception as exc:
751	n/a	self.exc = exc
752	n/a	self = None # Break the cycle
753	n/a	tester = Tester()
754	n/a	tester.dig()
755	n/a	ref = weakref.ref(tester)
756	n/a	del tester
757	n/a	self.assertIsNone(ref())
758	n/a
759	n/a
760	n/a	if __name__ == '__main__':
761	n/a	unittest.main()