Lib/test/test_unpack.py

   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)