1 import sys
2 import doctest
3 import unittest
4
5
6 doctests = """
7
8 Test simple loop with conditional
9
10 >>> sum(i*i for i in range(100) if i&1 == 1)
11 166650
12
13 Test simple nesting
14
15 >>> list((i,j) for i in range(3) for j in range(4) )
16 [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
17
18 Test nesting with the inner expression dependent on the outer
19
20 >>> list((i,j) for i in range(4) for j in range(i) )
21 [(1, 0), (2, 0), (2, 1), (3, 0), (3, 1), (3, 2)]
22
23 Test the idiom for temporary variable assignment in comprehensions.
24
25 >>> list((j*j for i in range(4) for j in [i+1]))
26 [1, 4, 9, 16]
27 >>> list((j*k for i in range(4) for j in [i+1] for k in [j+1]))
28 [2, 6, 12, 20]
29 >>> list((j*k for i in range(4) for j, k in [(i+1, i+2)]))
30 [2, 6, 12, 20]
31
32 Not assignment
33
34 >>> list((i*i for i in [*range(4)]))
35 [0, 1, 4, 9]
36 >>> list((i*i for i in (*range(4),)))
37 [0, 1, 4, 9]
38
39 Make sure the induction variable is not exposed
40
41 >>> i = 20
42 >>> sum(i*i for i in range(100))
43 328350
44 >>> i
45 20
46
47 Test first class
48
49 >>> g = (i*i for i in range(4))
50 >>> type(g)
51 <class 'generator'>
52 >>> list(g)
53 [0, 1, 4, 9]
54
55 Test direct calls to next()
56
57 >>> g = (i*i for i in range(3))
58 >>> next(g)
59 0
60 >>> next(g)
61 1
62 >>> next(g)
63 4
64 >>> next(g)
65 Traceback (most recent call last):
66 File "<pyshell#21>", line 1, in -toplevel-
67 next(g)
68 StopIteration
69
70 Does it stay stopped?
71
72 >>> next(g)
73 Traceback (most recent call last):
74 File "<pyshell#21>", line 1, in -toplevel-
75 next(g)
76 StopIteration
77 >>> list(g)
78 []
79
80 Test running gen when defining function is out of scope
81
82 >>> def f(n):
83 ... return (i*i for i in range(n))
84 >>> list(f(10))
85 [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
86
87 >>> def f(n):
88 ... return ((i,j) for i in range(3) for j in range(n))
89 >>> list(f(4))
90 [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
91 >>> def f(n):
92 ... return ((i,j) for i in range(3) for j in range(4) if j in range(n))
93 >>> list(f(4))
94 [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
95 >>> list(f(2))
96 [(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1)]
97
98 Verify that parenthesis are required in a statement
99
100 >>> def f(n):
101 ... return i*i for i in range(n)
102 Traceback (most recent call last):
103 ...
104 SyntaxError: invalid syntax
105
106 Verify that parenthesis are required when used as a keyword argument value
107
108 >>> dict(a = i for i in range(10))
109 Traceback (most recent call last):
110 ...
111 SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
112
113 Verify that parenthesis are required when used as a keyword argument value
114
115 >>> dict(a = (i for i in range(10))) #doctest: +ELLIPSIS
116 {'a': <generator object <genexpr> at ...>}
117
118 Verify early binding for the outermost for-expression
119
120 >>> x=10
121 >>> g = (i*i for i in range(x))
122 >>> x = 5
123 >>> list(g)
124 [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
125
126 Verify that the outermost for-expression makes an immediate check
127 for iterability
128
129 >>> (i for i in 6)
130 Traceback (most recent call last):
131 File "<pyshell#4>", line 1, in -toplevel-
132 (i for i in 6)
133 TypeError: 'int' object is not iterable
134
135 Verify late binding for the outermost if-expression
136
137 >>> include = (2,4,6,8)
138 >>> g = (i*i for i in range(10) if i in include)
139 >>> include = (1,3,5,7,9)
140 >>> list(g)
141 [1, 9, 25, 49, 81]
142
143 Verify late binding for the innermost for-expression
144
145 >>> g = ((i,j) for i in range(3) for j in range(x))
146 >>> x = 4
147 >>> list(g)
148 [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
149
150 Verify re-use of tuples (a side benefit of using genexps over listcomps)
151
152 >>> tupleids = list(map(id, ((i,i) for i in range(10))))
153 >>> int(max(tupleids) - min(tupleids))
154 0
155
156 Verify that syntax error's are raised for genexps used as lvalues
157
158 >>> (y for y in (1,2)) = 10
159 Traceback (most recent call last):
160 ...
161 SyntaxError: cannot assign to generator expression
162
163 >>> (y for y in (1,2)) += 10
164 Traceback (most recent call last):
165 ...
166 SyntaxError: 'generator expression' is an illegal expression for augmented assignment
167
168
169 ########### Tests borrowed from or inspired by test_generators.py ############
170
171 Make a generator that acts like range()
172
173 >>> yrange = lambda n: (i for i in range(n))
174 >>> list(yrange(10))
175 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
176
177 Generators always return to the most recent caller:
178
179 >>> def creator():
180 ... r = yrange(5)
181 ... print("creator", next(r))
182 ... return r
183 >>> def caller():
184 ... r = creator()
185 ... for i in r:
186 ... print("caller", i)
187 >>> caller()
188 creator 0
189 caller 1
190 caller 2
191 caller 3
192 caller 4
193
194 Generators can call other generators:
195
196 >>> def zrange(n):
197 ... for i in yrange(n):
198 ... yield i
199 >>> list(zrange(5))
200 [0, 1, 2, 3, 4]
201
202
203 Verify that a gen exp cannot be resumed while it is actively running:
204
205 >>> g = (next(me) for i in range(10))
206 >>> me = g
207 >>> next(me)
208 Traceback (most recent call last):
209 File "<pyshell#30>", line 1, in -toplevel-
210 next(me)
211 File "<pyshell#28>", line 1, in <generator expression>
212 g = (next(me) for i in range(10))
213 ValueError: generator already executing
214
215 Verify exception propagation
216
217 >>> g = (10 // i for i in (5, 0, 2))
218 >>> next(g)
219 2
220 >>> next(g)
221 Traceback (most recent call last):
222 File "<pyshell#37>", line 1, in -toplevel-
223 next(g)
224 File "<pyshell#35>", line 1, in <generator expression>
225 g = (10 // i for i in (5, 0, 2))
226 ZeroDivisionError: integer division or modulo by zero
227 >>> next(g)
228 Traceback (most recent call last):
229 File "<pyshell#38>", line 1, in -toplevel-
230 next(g)
231 StopIteration
232
233 Make sure that None is a valid return value
234
235 >>> list(None for i in range(10))
236 [None, None, None, None, None, None, None, None, None, None]
237
238 Check that generator attributes are present
239
240 >>> g = (i*i for i in range(3))
241 >>> expected = set(['gi_frame', 'gi_running'])
242 >>> set(attr for attr in dir(g) if not attr.startswith('__')) >= expected
243 True
244
245 >>> from test.support import HAVE_DOCSTRINGS
246 >>> print(g.__next__.__doc__ if HAVE_DOCSTRINGS else 'Implement next(self).')
247 Implement next(self).
248 >>> import types
249 >>> isinstance(g, types.GeneratorType)
250 True
251
252 Check the __iter__ slot is defined to return self
253
254 >>> iter(g) is g
255 True
256
257 Verify that the running flag is set properly
258
259 >>> g = (me.gi_running for i in (0,1))
260 >>> me = g
261 >>> me.gi_running
262 0
263 >>> next(me)
264 1
265 >>> me.gi_running
266 0
267
268 Verify that genexps are weakly referencable
269
270 >>> import weakref
271 >>> g = (i*i for i in range(4))
272 >>> wr = weakref.ref(g)
273 >>> wr() is g
274 True
275 >>> p = weakref.proxy(g)
276 >>> list(p)
277 [0, 1, 4, 9]
278
279
280 """
281
282 # Trace function can throw off the tuple reuse test.
283 if hasattr(sys, 'gettrace') and sys.gettrace():
284 __test__ = {}
285 else:
286 __test__ = {'doctests' : doctests}
287
288 def load_tests(loader, tests, pattern):
289 tests.addTest(doctest.DocTestSuite())
290 return tests
291
292
293 if __name__ == "__main__":
294 unittest.main()