summaryrefslogtreecommitdiff
path: root/Lib/test/test_unpack_ex.py
blob: 74346b42054f8e51c096d77119a726f679828799 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
# Tests for extended unpacking, starred expressions.

doctests = """

Unpack tuple

    >>> t = (1, 2, 3)
    >>> a, *b, c = t
    >>> a == 1 and b == [2] and c == 3
    True

Unpack list

    >>> l = [4, 5, 6]
    >>> a, *b = l
    >>> a == 4 and b == [5, 6]
    True

Unpack implied tuple

    >>> *a, = 7, 8, 9
    >>> a == [7, 8, 9]
    True

Unpack string... fun!

    >>> a, *b = 'one'
    >>> a == 'o' and b == ['n', 'e']
    True

Unpack long sequence

    >>> a, b, c, *d, e, f, g = range(10)
    >>> (a, b, c, d, e, f, g) == (0, 1, 2, [3, 4, 5, 6], 7, 8, 9)
    True

Unpack short sequence

    >>> a, *b, c = (1, 2)
    >>> a == 1 and c == 2 and b == []
    True

Unpack generic sequence

    >>> class Seq:
    ...     def __getitem__(self, i):
    ...         if i >= 0 and i < 3: return i
    ...         raise IndexError
    ...
    >>> a, *b = Seq()
    >>> a == 0 and b == [1, 2]
    True

Unpack in for statement

    >>> for a, *b, c in [(1,2,3), (4,5,6,7)]:
    ...     print(a, b, c)
    ...
    1 [2] 3
    4 [5, 6] 7

Unpack in list

    >>> [a, *b, c] = range(5)
    >>> a == 0 and b == [1, 2, 3] and c == 4
    True

Multiple targets

    >>> a, *b, c = *d, e = range(5)
    >>> a == 0 and b == [1, 2, 3] and c == 4 and d == [0, 1, 2, 3] and e == 4
    True

Assignment unpacking

    >>> a, b, *c = range(5)
    >>> a, b, c
    (0, 1, [2, 3, 4])
    >>> *a, b, c = a, b, *c
    >>> a, b, c
    ([0, 1, 2], 3, 4)

Set display element unpacking

    >>> a = [1, 2, 3]
    >>> sorted({1, *a, 0, 4})
    [0, 1, 2, 3, 4]

    >>> {1, *1, 0, 4}
    Traceback (most recent call last):
      ...
    TypeError: 'int' object is not iterable

Dict display element unpacking

    >>> kwds = {'z': 0, 'w': 12}
    >>> sorted({'x': 1, 'y': 2, **kwds}.items())
    [('w', 12), ('x', 1), ('y', 2), ('z', 0)]

    >>> sorted({**{'x': 1}, 'y': 2, **{'z': 3}}.items())
    [('x', 1), ('y', 2), ('z', 3)]

    >>> sorted({**{'x': 1}, 'y': 2, **{'x': 3}}.items())
    [('x', 3), ('y', 2)]

    >>> sorted({**{'x': 1}, **{'x': 3}, 'x': 4}.items())
    [('x', 4)]

    >>> {**{}}
    {}

    >>> a = {}
    >>> {**a}[0] = 1
    >>> a
    {}

    >>> {**1}
    Traceback (most recent call last):
    ...
    TypeError: 'int' object is not a mapping

    >>> {**[]}
    Traceback (most recent call last):
    ...
    TypeError: 'list' object is not a mapping

    >>> len(eval("{" + ", ".join("**{{{}: {}}}".format(i, i)
    ...                          for i in range(1000)) + "}"))
    1000

    >>> {0:1, **{0:2}, 0:3, 0:4}
    {0: 4}

List comprehension element unpacking

    >>> a, b, c = [0, 1, 2], 3, 4
    >>> [*a, b, c]
    [0, 1, 2, 3, 4]

    >>> l = [a, (3, 4), {5}, {6: None}, (i for i in range(7, 10))]
    >>> [*item for item in l]
    Traceback (most recent call last):
    ...
    SyntaxError: iterable unpacking cannot be used in comprehension

    >>> [*[0, 1] for i in range(10)]
    Traceback (most recent call last):
    ...
    SyntaxError: iterable unpacking cannot be used in comprehension

    >>> [*'a' for i in range(10)]
    Traceback (most recent call last):
    ...
    SyntaxError: iterable unpacking cannot be used in comprehension

    >>> [*[] for i in range(10)]
    Traceback (most recent call last):
    ...
    SyntaxError: iterable unpacking cannot be used in comprehension

Generator expression in function arguments

    >>> list(*x for x in (range(5) for i in range(3)))
    Traceback (most recent call last):
    ...
        list(*x for x in (range(5) for i in range(3)))
                  ^
    SyntaxError: invalid syntax

    >>> dict(**x for x in [{1:2}])
    Traceback (most recent call last):
    ...
        dict(**x for x in [{1:2}])
                   ^
    SyntaxError: invalid syntax

Iterable argument unpacking

    >>> print(*[1], *[2], 3)
    1 2 3

Make sure that they don't corrupt the passed-in dicts.

    >>> def f(x, y):
    ...     print(x, y)
    ...
    >>> original_dict = {'x': 1}
    >>> f(**original_dict, y=2)
    1 2
    >>> original_dict
    {'x': 1}

Now for some failures

Make sure the raised errors are right for keyword argument unpackings

    >>> from collections.abc import MutableMapping
    >>> class CrazyDict(MutableMapping):
    ...     def __init__(self):
    ...         self.d = {}
    ...
    ...     def __iter__(self):
    ...         for x in self.d.__iter__():
    ...             if x == 'c':
    ...                 self.d['z'] = 10
    ...             yield x
    ...
    ...     def __getitem__(self, k):
    ...         return self.d[k]
    ...
    ...     def __len__(self):
    ...         return len(self.d)
    ...
    ...     def __setitem__(self, k, v):
    ...         self.d[k] = v
    ...
    ...     def __delitem__(self, k):
    ...         del self.d[k]
    ...
    >>> d = CrazyDict()
    >>> d.d = {chr(ord('a') + x): x for x in range(5)}
    >>> e = {**d}
    Traceback (most recent call last):
    ...
    RuntimeError: dictionary changed size during iteration

    >>> d.d = {chr(ord('a') + x): x for x in range(5)}
    >>> def f(**kwargs): print(kwargs)
    >>> f(**d)
    Traceback (most recent call last):
    ...
    RuntimeError: dictionary changed size during iteration

Overridden parameters

    >>> f(x=5, **{'x': 3}, y=2)
    Traceback (most recent call last):
      ...
    TypeError: f() got multiple values for keyword argument 'x'

    >>> f(**{'x': 3}, x=5, y=2)
    Traceback (most recent call last):
      ...
    TypeError: f() got multiple values for keyword argument 'x'

    >>> f(**{'x': 3}, **{'x': 5}, y=2)
    Traceback (most recent call last):
      ...
    TypeError: f() got multiple values for keyword argument 'x'

    >>> f(x=5, **{'x': 3}, **{'x': 2})
    Traceback (most recent call last):
      ...
    TypeError: f() got multiple values for keyword argument 'x'

    >>> f(**{1: 3}, **{1: 5})
    Traceback (most recent call last):
      ...
    TypeError: f() keywords must be strings

Unpacking non-sequence

    >>> a, *b = 7
    Traceback (most recent call last):
      ...
    TypeError: 'int' object is not iterable

Unpacking sequence too short

    >>> a, *b, c, d, e = Seq()
    Traceback (most recent call last):
      ...
    ValueError: not enough values to unpack (expected at least 4, got 3)

Unpacking sequence too short and target appears last

    >>> a, b, c, d, *e = Seq()
    Traceback (most recent call last):
      ...
    ValueError: not enough values to unpack (expected at least 4, got 3)

Unpacking a sequence where the test for too long raises a different kind of
error

    >>> class BozoError(Exception):
    ...     pass
    ...
    >>> class BadSeq:
    ...     def __getitem__(self, i):
    ...         if i >= 0 and i < 3:
    ...             return i
    ...         elif i == 3:
    ...             raise BozoError
    ...         else:
    ...             raise IndexError
    ...

Trigger code while not expecting an IndexError (unpack sequence too long, wrong
error)

    >>> a, *b, c, d, e = BadSeq()
    Traceback (most recent call last):
      ...
    test.test_unpack_ex.BozoError

Now some general starred expressions (all fail).

    >>> a, *b, c, *d, e = range(10) # doctest:+ELLIPSIS
    Traceback (most recent call last):
      ...
    SyntaxError: two starred expressions in assignment

    >>> [*b, *c] = range(10) # doctest:+ELLIPSIS
    Traceback (most recent call last):
      ...
    SyntaxError: two starred expressions in assignment

    >>> *a = range(10) # doctest:+ELLIPSIS
    Traceback (most recent call last):
      ...
    SyntaxError: starred assignment target must be in a list or tuple

    >>> *a # doctest:+ELLIPSIS
    Traceback (most recent call last):
      ...
    SyntaxError: can't use starred expression here

    >>> *1 # doctest:+ELLIPSIS
    Traceback (most recent call last):
      ...
    SyntaxError: can't use starred expression here

    >>> x = *a # doctest:+ELLIPSIS
    Traceback (most recent call last):
      ...
    SyntaxError: can't use starred expression here

Some size constraints (all fail.)

    >>> s = ", ".join("a%d" % i for i in range(1<<8)) + ", *rest = range(1<<8 + 1)"
    >>> compile(s, 'test', 'exec') # doctest:+ELLIPSIS
    Traceback (most recent call last):
     ...
    SyntaxError: too many expressions in star-unpacking assignment

    >>> s = ", ".join("a%d" % i for i in range(1<<8 + 1)) + ", *rest = range(1<<8 + 2)"
    >>> compile(s, 'test', 'exec') # doctest:+ELLIPSIS
    Traceback (most recent call last):
     ...
    SyntaxError: too many expressions in star-unpacking assignment

(there is an additional limit, on the number of expressions after the
'*rest', but it's 1<<24 and testing it takes too much memory.)

"""

__test__ = {'doctests' : doctests}

def test_main(verbose=False):
    import sys
    from test import support
    from test import test_unpack_ex
    support.run_doctest(test_unpack_ex, verbose)

if __name__ == "__main__":
    test_main(verbose=True)