Avetis KAZARIAN wrote: > Gary Herron wrote: >> The question now is: Why do you care? The properties of strings do >> not depend on the implementation's choice, so you shouldn't care because >> of programming considerations. Perhaps it's just a matter of curiosity >> on your part. >> >> Gary Herron > > Well, it's not about curiosity, it's more about performance. > > I will make a PHP example (a really quite simple ) > > PHP : > > Stat 1 : $aVeryLongString == $anOtherVeryLongString > Stat 2 : $aVeryLongString === $anOtherVeryLongString > > Stat 2 is really faster than Stat 1 (due to the binary comparison) > > As I said, I'm coming from PHP, so I was wondering if there was such a > difference in Python. > > Because I was trying to use "is" as for "===".
Suppose you write a = b Thereafter, unless some further assignment is made to either a or b, you are guaranteed that "a is b" returns True. This is pretty much the only guarantee you have. There is no guarantee (across all implementations) that a = some-expression b = some-equivalent-expression will leave "a is b" True. Does PHP really keep only one copy of every string? Sounds like that could slow string creation down a little. Essentially it's keeping all strings in a set. Of course you could do that in Python if you wanted, but it would certainly slow things down. Anyway, thanks for looking at Python. I hope you continue to enjoy it! regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
