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1 doctests = """ |
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2 |
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3 Unpack tuple |
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4 |
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5 >>> t = (1, 2, 3) |
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6 >>> a, b, c = t |
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7 >>> a == 1 and b == 2 and c == 3 |
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8 True |
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9 |
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10 Unpack list |
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11 |
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12 >>> l = [4, 5, 6] |
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13 >>> a, b, c = l |
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14 >>> a == 4 and b == 5 and c == 6 |
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15 True |
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16 |
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17 Unpack implied tuple |
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18 |
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19 >>> a, b, c = 7, 8, 9 |
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20 >>> a == 7 and b == 8 and c == 9 |
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21 True |
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22 |
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23 Unpack string... fun! |
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24 |
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25 >>> a, b, c = 'one' |
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26 >>> a == 'o' and b == 'n' and c == 'e' |
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27 True |
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28 |
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29 Unpack generic sequence |
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30 |
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31 >>> class Seq: |
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32 ... def __getitem__(self, i): |
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33 ... if i >= 0 and i < 3: return i |
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34 ... raise IndexError |
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35 ... |
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36 >>> a, b, c = Seq() |
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37 >>> a == 0 and b == 1 and c == 2 |
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38 True |
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39 |
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40 Single element unpacking, with extra syntax |
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41 |
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42 >>> st = (99,) |
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43 >>> sl = [100] |
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44 >>> a, = st |
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45 >>> a |
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46 99 |
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47 >>> b, = sl |
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48 >>> b |
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49 100 |
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50 |
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51 Now for some failures |
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52 |
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53 Unpacking non-sequence |
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54 |
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55 >>> a, b, c = 7 |
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56 Traceback (most recent call last): |
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57 ... |
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58 TypeError: 'int' object is not iterable |
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59 |
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60 Unpacking tuple of wrong size |
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61 |
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62 >>> a, b = t |
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63 Traceback (most recent call last): |
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64 ... |
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65 ValueError: too many values to unpack |
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66 |
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67 Unpacking tuple of wrong size |
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68 |
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69 >>> a, b = l |
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70 Traceback (most recent call last): |
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71 ... |
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72 ValueError: too many values to unpack |
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73 |
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74 Unpacking sequence too short |
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75 |
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76 >>> a, b, c, d = Seq() |
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77 Traceback (most recent call last): |
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78 ... |
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79 ValueError: need more than 3 values to unpack |
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80 |
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81 Unpacking sequence too long |
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82 |
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83 >>> a, b = Seq() |
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84 Traceback (most recent call last): |
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85 ... |
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86 ValueError: too many values to unpack |
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87 |
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88 Unpacking a sequence where the test for too long raises a different kind of |
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89 error |
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90 |
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91 >>> class BozoError(Exception): |
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92 ... pass |
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93 ... |
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94 >>> class BadSeq: |
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95 ... def __getitem__(self, i): |
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96 ... if i >= 0 and i < 3: |
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97 ... return i |
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98 ... elif i == 3: |
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99 ... raise BozoError |
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100 ... else: |
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101 ... raise IndexError |
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102 ... |
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103 |
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104 Trigger code while not expecting an IndexError (unpack sequence too long, wrong |
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105 error) |
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106 |
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107 >>> a, b, c, d, e = BadSeq() |
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108 Traceback (most recent call last): |
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109 ... |
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110 BozoError |
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111 |
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112 Trigger code while expecting an IndexError (unpack sequence too short, wrong |
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113 error) |
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114 |
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115 >>> a, b, c = BadSeq() |
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116 Traceback (most recent call last): |
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117 ... |
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118 BozoError |
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119 |
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120 """ |
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121 |
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122 __test__ = {'doctests' : doctests} |
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123 |
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124 def test_main(verbose=False): |
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125 from test import test_support |
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126 from test import test_unpack |
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127 test_support.run_doctest(test_unpack, verbose) |
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128 |
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129 if __name__ == "__main__": |
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130 test_main(verbose=True) |