Favorite non-python language trick?

[Peter Otten]

Steven D'Aprano wrote:

> On Sat, 25 Jun 2005 21:30:26 +0200, Peter Otten wrote:
> 
>> Mandus wrote:
>> 
>>> By using the builtin reduce, I
>>> move the for-loop into the c-code which performs better.
>> 
>> No. There is no hope of ever writing fast code when you do not actually
>> measure its performance.
> 
> Good grief! You've been spying on Mandus! How else could you possibly know
> that he doesn't measure performance? Are you running a key-logger on his
> machine? *wink*

His mentioning reduce() as a performance panacea was a strong indication
even without looking over his shoulders. He filled in some conditions in a
later post, but "[U]sing reduce ... performs better [than a for-loop]" is
just wrong.

> For the record, perhaps now is a good time to mention that even Guido
> recommended the use of map, filter and reduce in some circumstances:

Personally I wouldn't rely on authority when I can measure without much
hassle. And the lesson I take from Guido's essay is rather how he got to
his conclusions than what his actual findings were. After all, Python may
have advanced a bit since he wrote the text.

> Do we really need to profile our code every single time to know this?

No. Only if we care about the performance of a particular piece. And if we
do we are sometimes in for a surprise.

> Isn't it reasonable to just say, "I use join because it is faster than
> adding strings" without being abused for invalid optimization?

OK, I am making a guess: "".join(strings) is more often faster than
naive string addition than reduce() wins over a for-loop.

I don't think my pointed comment qualifies as "abuse", by the way.

Peter