diff -r ffa851df0825 -r 2fb8b9db1c86 symbian-qemu-0.9.1-12/python-2.6.1/Demo/classes/Rev.py --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/symbian-qemu-0.9.1-12/python-2.6.1/Demo/classes/Rev.py Fri Jul 31 15:01:17 2009 +0100 @@ -0,0 +1,95 @@ +''' +A class which presents the reverse of a sequence without duplicating it. +From: "Steven D. Majewski" + +It works on mutable or inmutable sequences. + +>>> chars = list(Rev('Hello World!')) +>>> print ''.join(chars) +!dlroW olleH + +The .forw is so you can use anonymous sequences in __init__, and still +keep a reference the forward sequence. ) +If you give it a non-anonymous mutable sequence, the reverse sequence +will track the updated values. ( but not reassignment! - another +good reason to use anonymous values in creating the sequence to avoid +confusion. Maybe it should be change to copy input sequence to break +the connection completely ? ) + +>>> nnn = range(3) +>>> rnn = Rev(nnn) +>>> for n in rnn: print n +... +2 +1 +0 +>>> for n in range(4, 6): nnn.append(n) # update nnn +... +>>> for n in rnn: print n # prints reversed updated values +... +5 +4 +2 +1 +0 +>>> nnn = nnn[1:-1] +>>> nnn +[1, 2, 4] +>>> for n in rnn: print n # prints reversed values of old nnn +... +5 +4 +2 +1 +0 + +# +>>> WH = Rev('Hello World!') +>>> print WH.forw, WH.back +Hello World! !dlroW olleH +>>> nnn = Rev(range(1, 10)) +>>> print nnn.forw +[1, 2, 3, 4, 5, 6, 7, 8, 9] +>>> print nnn.back +[9, 8, 7, 6, 5, 4, 3, 2, 1] + +>>> rrr = Rev(nnn) +>>> rrr +<1, 2, 3, 4, 5, 6, 7, 8, 9> + +''' + +class Rev: + def __init__(self, seq): + self.forw = seq + self.back = self + + def __len__(self): + return len(self.forw) + + def __getitem__(self, j): + return self.forw[-(j + 1)] + + def __repr__(self): + seq = self.forw + if isinstance(seq, list): + wrap = '[]' + sep = ', ' + elif isinstance(seq, tuple): + wrap = '()' + sep = ', ' + elif isinstance(seq, str): + wrap = '' + sep = '' + else: + wrap = '<>' + sep = ', ' + outstrs = [str(item) for item in self.back] + return wrap[:1] + sep.join(outstrs) + wrap[-1:] + +def _test(): + import doctest, Rev + return doctest.testmod(Rev) + +if __name__ == "__main__": + _test()