[New-bugs-announce] [issue9120] Reduce pickle size for an empty set

[Alexander Belopolsky]

New submission from Alexander Belopolsky <belopolsky at users.sourceforge.net>:

Empty sets are pickled as set([]).  The pickle contains serialization of an empty list that is passed to set constructor during unpickling:

>>> dis(dumps(set()))
    0: \x80 PROTO      3
    2: c    GLOBAL     'builtins set'
   16: q    BINPUT     0
   18: ]    EMPTY_LIST
   19: q    BINPUT     1
   21: \x85 TUPLE1
   22: q    BINPUT     2
   24: R    REDUCE
   25: q    BINPUT     3
   27: .    STOP

The proposed patch pickles empty set as set() instead:


>>> dis(dumps(set()))
    0: \x80 PROTO      3
    2: c    GLOBAL     'builtins set'
   16: q    BINPUT     0
   18: )    EMPTY_TUPLE
   19: R    REDUCE
   20: q    BINPUT     1
   22: .    STOP

----------
components: Interpreter Core
files: empty-set-pickle.diff
keywords: patch
messages: 108937
nosy: alexandre.vassalotti, belopolsky, pitrou
priority: normal
severity: normal
stage: patch review
status: open
title: Reduce pickle size for an empty set
type: feature request
versions: Python 3.2
Added file: http://bugs.python.org/file17804/empty-set-pickle.diff

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue9120>
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