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� V �Qc @ s< d Z d d d � � YZ d � Z e d k r8 e � n d S( s� A class which presents the reverse of a sequence without duplicating it. From: "Steven D. Majewski" <sdm7g@elvis.med.virginia.edu> 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> t Revc B s, e Z d � Z d � Z d � Z d � Z RS( c C s | | _ | | _ d S( N( t forwt back( t selft seq( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyt __init__? s c C s t | j � S( N( t lenR ( R ( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyt __len__C s c C s | j | d S( Ni ( R ( R t j( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyt __getitem__F s c C s� | j } t | t � r' d } d } nH t | t � rE d } d } n* t | t � rc d } d } n d } d } g | j D] } t | � ^ qy } | d | j | � | d S( Ns []s , s ()t s <>i i����( R t isinstancet listt tuplet strR t join( R R t wrapt sept itemt outstrs( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyt __repr__I s "( t __name__t __module__R R R R ( ( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyR > s c C s% d d l } d d l } | j | � S( Ni����( t doctestR t testmod( R R ( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyt _testZ s t __main__N( ( t __doc__R R R ( ( ( s( /usr/lib64/python2.7/Demo/classes/Rev.pyt <module>< s