4710c53dca
These files are a subset of the python-2.7.2.tgz distribution from python.org. Changed files from PyMod-2.7.2 have been copied into the corresponding directories of this tree, replacing the original files in the distribution. Signed-off-by: daryl.mcdaniel@intel.com git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13197 6f19259b-4bc3-4df7-8a09-765794883524
96 lines
2.1 KiB
Python
96 lines
2.1 KiB
Python
'''
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A class which presents the reverse of a sequence without duplicating it.
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From: "Steven D. Majewski" <sdm7g@elvis.med.virginia.edu>
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It works on mutable or inmutable sequences.
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>>> chars = list(Rev('Hello World!'))
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>>> print ''.join(chars)
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!dlroW olleH
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The .forw is so you can use anonymous sequences in __init__, and still
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keep a reference the forward sequence. )
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If you give it a non-anonymous mutable sequence, the reverse sequence
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will track the updated values. ( but not reassignment! - another
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good reason to use anonymous values in creating the sequence to avoid
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confusion. Maybe it should be change to copy input sequence to break
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the connection completely ? )
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>>> nnn = range(3)
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>>> rnn = Rev(nnn)
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>>> for n in rnn: print n
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...
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2
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1
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0
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>>> for n in range(4, 6): nnn.append(n) # update nnn
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...
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>>> for n in rnn: print n # prints reversed updated values
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...
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5
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4
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2
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1
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0
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>>> nnn = nnn[1:-1]
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>>> nnn
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[1, 2, 4]
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>>> for n in rnn: print n # prints reversed values of old nnn
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...
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5
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4
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2
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1
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0
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#
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>>> WH = Rev('Hello World!')
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>>> print WH.forw, WH.back
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Hello World! !dlroW olleH
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>>> nnn = Rev(range(1, 10))
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>>> print nnn.forw
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[1, 2, 3, 4, 5, 6, 7, 8, 9]
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>>> print nnn.back
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[9, 8, 7, 6, 5, 4, 3, 2, 1]
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>>> rrr = Rev(nnn)
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>>> rrr
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<1, 2, 3, 4, 5, 6, 7, 8, 9>
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'''
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class Rev:
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def __init__(self, seq):
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self.forw = seq
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self.back = self
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def __len__(self):
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return len(self.forw)
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def __getitem__(self, j):
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return self.forw[-(j + 1)]
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def __repr__(self):
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seq = self.forw
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if isinstance(seq, list):
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wrap = '[]'
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sep = ', '
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elif isinstance(seq, tuple):
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wrap = '()'
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sep = ', '
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elif isinstance(seq, str):
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wrap = ''
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sep = ''
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else:
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wrap = '<>'
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sep = ', '
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outstrs = [str(item) for item in self.back]
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return wrap[:1] + sep.join(outstrs) + wrap[-1:]
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def _test():
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import doctest, Rev
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return doctest.testmod(Rev)
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if __name__ == "__main__":
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_test()
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