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
|
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, c = l
>>> a == 4 and b == 5 and c == 6
True
Unpack implied tuple
>>> a, b, c = 7, 8, 9
>>> a == 7 and b == 8 and c == 9
True
Unpack string... fun!
>>> a, b, c = 'one'
>>> a == 'o' and b == 'n' and c == 'e'
True
Unpack generic sequence
>>> class Seq:
... def __getitem__(self, i):
... if i >= 0 and i < 3: return i
... raise IndexError
...
>>> a, b, c = Seq()
>>> a == 0 and b == 1 and c == 2
True
Single element unpacking, with extra syntax
>>> st = (99,)
>>> sl = [100]
>>> a, = st
>>> a
99
>>> b, = sl
>>> b
100
Now for some failures
Unpacking non-sequence
>>> a, b, c = 7
Traceback (most recent call last):
...
TypeError: cannot unpack non-iterable int object
Unpacking tuple of wrong size
>>> a, b = t
Traceback (most recent call last):
...
ValueError: too many values to unpack (expected 2)
Unpacking tuple of wrong size
>>> a, b = l
Traceback (most recent call last):
...
ValueError: too many values to unpack (expected 2)
Unpacking sequence too short
>>> a, b, c, d = Seq()
Traceback (most recent call last):
...
ValueError: not enough values to unpack (expected 4, got 3)
Unpacking sequence too long
>>> a, b = Seq()
Traceback (most recent call last):
...
ValueError: too many values to unpack (expected 2)
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.BozoError
Trigger code while expecting an IndexError (unpack sequence too short, wrong
error)
>>> a, b, c = BadSeq()
Traceback (most recent call last):
...
test.test_unpack.BozoError
Allow unpacking empty iterables
>>> () = []
>>> [] = ()
>>> [] = []
>>> () = ()
Unpacking non-iterables should raise TypeError
>>> () = 42
Traceback (most recent call last):
...
TypeError: cannot unpack non-iterable int object
Unpacking to an empty iterable should raise ValueError
>>> () = [42]
Traceback (most recent call last):
...
ValueError: too many values to unpack (expected 0)
"""
__test__ = {'doctests' : doctests}
def test_main(verbose=False):
from test import support
from test import test_unpack
support.run_doctest(test_unpack, verbose)
if __name__ == "__main__":
test_main(verbose=True)
|
