On Jan 4, 2008 11:50 AM, A.M. Kuchling <[EMAIL PROTECTED]> wrote: > This post describes work aimed at getting Django to run on Jython: > http://zyasoft.com/pythoneering/2008/01/django-on-jython-minding-gap.html > > One outstanding issue is whether to use Java's ConcurrentHashMap type > to underly Jython's dict type. See > <http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/ConcurrentHashMap.html>. > > ConcurrentHashMap scales better in the face of threading because it > doesn't lock the whole table when updating it, but iterating over the > map can return elements in a different order each time. This would > mean that list(dict_var) doesn't return values in the same order as a > later call to list(dict_var), even if dict_var hasn't been modified. > > Why? Under the hood, there are 32 different locks, each guarding a > subset of the hash buckets, so if there are multiple threads iterating > over the dictionary, they may not go through the buckets in order. > <http://www.ibm.com/developerworks/java/library/j-jtp08223/> discusses > the implementation, at least in 2003. > > So, do Python implementations need to guarantee that list(dict_var) == > a later result from list(dict_var)?
What code would break if we loosened this restriction? I guess defining d.items() as zip(d.keys(), d.values()) would no longer fly, but does anyone actually depend on this? Just like we changed how we think about auto-closing files once Jython came along, I think this is at least worth considering. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
