67 lines
1.7 KiB
Plaintext
67 lines
1.7 KiB
Plaintext
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PEP: 270
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Title: uniq method for list objects
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Version: $Revision$
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Last-Modified: $Date$
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Author: jp@demonseed.net (Jason Petrone)
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Status: Draft
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Type: Standards Track
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Created: 21-Aug-2001
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Python-Version: 2.2
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Post-History:
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Abstract
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This PEP proposes adding a method for removing duplicate elements to
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the list object.
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Rationale
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Removing duplicates from a list is a common task. I think it is
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useful and general enough to belong as a method in list objects.
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It also has potential for faster execution when implemented in C,
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especially if optimization using hashing or sorted cannot be used.
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On comp.lang.python there are many, many, posts[1] asking about
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the best way to do this task. Its a little tricky to implement
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optimally and it would be nice to save people the trouble of
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figuring it out themselves.
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Considerations
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Tim Peters suggests trying to use a hash table, then trying to
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sort, and finally falling back on brute force[2]. Should uniq
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maintain list order at the expense of speed?
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Is it spelled 'uniq' or 'unique'?
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Reference Implementation
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I've written the brute force version. Its about 20 lines of code
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in listobject.c. Adding support for hash table and sorted
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duplicate removal would only take another hour or so.
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References
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[1] http://groups.google.com/groups?as_q=duplicates&as_ugroup=comp.lang.python
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[2] Tim Peters unique() entry in the Python cookbook:
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http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52560/index_txt
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Copyright
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This document has been placed in the public domain.
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Local Variables:
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mode: indented-text
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fill-column: 70
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End:
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