[Python-Dev] redefining is (original) (raw)

François Pinard pinard at iro.umontreal.ca
Sat Mar 20 08:45:07 EST 2004

[Tim Peters]

buf is ''

There is question which traversed my mind recently. While I would never use is' between ordinary strings, I might be tempted to use is' between explicitely interned strings, under the hypothesis that for example:

a = intern('a b')
b = intern('a b')
a is b

dependably prints `True'. However, I remember a thread in this forum by which strings might be un-interned on the fly -- but do not remember the details; I presume it was for strings which the garbage collector may not reach anymore.

There are a few real-life cases where speed considerations would invite programmers to use is' over ==' for strings, given they all get interned to start with so the speed-up could be gleaned later. The fact that `is' exposes the implementation is quite welcome in such cases.

-- François Pinard http://www.iro.umontreal.ca/~pinard

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