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      1 doctests = """
      2 
      3 Unpack tuple
      4 
      5     >>> t = (1, 2, 3)
      6     >>> a, b, c = t
      7     >>> a == 1 and b == 2 and c == 3
      8     True
      9 
     10 Unpack list
     11 
     12     >>> l = [4, 5, 6]
     13     >>> a, b, c = l
     14     >>> a == 4 and b == 5 and c == 6
     15     True
     16 
     17 Unpack implied tuple
     18 
     19     >>> a, b, c = 7, 8, 9
     20     >>> a == 7 and b == 8 and c == 9
     21     True
     22 
     23 Unpack string... fun!
     24 
     25     >>> a, b, c = 'one'
     26     >>> a == 'o' and b == 'n' and c == 'e'
     27     True
     28 
     29 Unpack generic sequence
     30 
     31     >>> class Seq:
     32     ...     def __getitem__(self, i):
     33     ...         if i >= 0 and i < 3: return i
     34     ...         raise IndexError
     35     ...
     36     >>> a, b, c = Seq()
     37     >>> a == 0 and b == 1 and c == 2
     38     True
     39 
     40 Single element unpacking, with extra syntax
     41 
     42     >>> st = (99,)
     43     >>> sl = [100]
     44     >>> a, = st
     45     >>> a
     46     99
     47     >>> b, = sl
     48     >>> b
     49     100
     50 
     51 Now for some failures
     52 
     53 Unpacking non-sequence
     54 
     55     >>> a, b, c = 7
     56     Traceback (most recent call last):
     57       ...
     58     TypeError: 'int' object is not iterable
     59 
     60 Unpacking tuple of wrong size
     61 
     62     >>> a, b = t
     63     Traceback (most recent call last):
     64       ...
     65     ValueError: too many values to unpack
     66 
     67 Unpacking tuple of wrong size
     68 
     69     >>> a, b = l
     70     Traceback (most recent call last):
     71       ...
     72     ValueError: too many values to unpack
     73 
     74 Unpacking sequence too short
     75 
     76     >>> a, b, c, d = Seq()
     77     Traceback (most recent call last):
     78       ...
     79     ValueError: need more than 3 values to unpack
     80 
     81 Unpacking sequence too long
     82 
     83     >>> a, b = Seq()
     84     Traceback (most recent call last):
     85       ...
     86     ValueError: too many values to unpack
     87 
     88 Unpacking a sequence where the test for too long raises a different kind of
     89 error
     90 
     91     >>> class BozoError(Exception):
     92     ...     pass
     93     ...
     94     >>> class BadSeq:
     95     ...     def __getitem__(self, i):
     96     ...         if i >= 0 and i < 3:
     97     ...             return i
     98     ...         elif i == 3:
     99     ...             raise BozoError
    100     ...         else:
    101     ...             raise IndexError
    102     ...
    103 
    104 Trigger code while not expecting an IndexError (unpack sequence too long, wrong
    105 error)
    106 
    107     >>> a, b, c, d, e = BadSeq()
    108     Traceback (most recent call last):
    109       ...
    110     BozoError
    111 
    112 Trigger code while expecting an IndexError (unpack sequence too short, wrong
    113 error)
    114 
    115     >>> a, b, c = BadSeq()
    116     Traceback (most recent call last):
    117       ...
    118     BozoError
    119 
    120 """
    121 
    122 __test__ = {'doctests' : doctests}
    123 
    124 def test_main(verbose=False):
    125     from test import test_support
    126     from test import test_unpack
    127     test_support.run_doctest(test_unpack, verbose)
    128 
    129 if __name__ == "__main__":
    130     test_main(verbose=True)
    131