[Python-Dev] New stringbench benchmark results (original) (raw)

Steven D'Aprano steve at pearwood.info
Fri Oct 7 03:19:20 CEST 2011

Victor Stinner wrote:

Hum, copy-paste failure, I wrote numbers in the wrong order, it's:

(test: Python 3.2 => Python 3.3) "A".join(["Bob"]*100)): 0.92 => 2.11 ("C"+"AB"*300).rfind("CA"): 0.57 => 1.03 ("A" + ("Z"1281024)).replace("A", "BB", 1): 0.25 => 0.50 I improved str.replace(): it's now 5 times faster instead of 2 times slower for this specific benchmark :-) (or 10 times faster in Python 3.3 before/after my patch)

Talking about str.replace, I was surprised to see this behaviour in 3.2:

s = 'spam' t = s.replace('a', 'a') s is t False

Given that strings are immutable, would it not be an obvious optimization for replace to return the source string unchanged if the old and new substrings are equal, and avoid making a potentially expensive copy?

I note that if count is zero, the source string is returned unchanged:

t = s.replace('a', 'b', 0) t is s True

-- Steven

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