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: 'int' object is not iterable

Unpacking tuple of wrong size

    >>> a, b = t

    Traceback (most recent call last):

      ...

    ValueError: too many values to unpack

Unpacking tuple of wrong size

    >>> a, b = l

    Traceback (most recent call last):

      ...

    ValueError: too many values to unpack

Unpacking sequence too short

    >>> a, b, c, d = Seq()

    Traceback (most recent call last):

      ...

    ValueError: need more than 3 values to unpack

Unpacking sequence too long

    >>> a, b = Seq()

    Traceback (most recent call last):

      ...

    ValueError: too many values to unpack

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):

      ...

    BozoError

Trigger code while expecting an IndexError (unpack sequence too short, wrong

error)

    >>> a, b, c = BadSeq()

    Traceback (most recent call last):

      ...

    BozoError

"""

__test__ = {'doctests' : doctests}

def test_main(verbose=False):

    from test import test_support

    from test import test_unpack

    test_support.run_doctest(test_unpack, verbose)

if __name__ == "__main__":

    test_main(verbose=True)