[Tutor] list comprehension, testing for multiple conditions

[Pete O'Connell]

Ok thanks for the advice everyone.

Cheers
Pete

On Thu, Aug 23, 2012 at 10:58 AM, Jerry Hill <malaclypse2 at gmail.com> wrote:
> On Wed, Aug 22, 2012 at 5:23 PM, Pete O'Connell <pedrooconnell at gmail.com> wrote:
>> OK maybe I am wrong about it being slow (I thought for loops were
>> slower than lis comprehensions). But I do know I need it to be as fast
>> as possible if I need to run it on a thousand files each with hundreds
>> of thousands of lines
>
> You're quite likely wrong about that.  The overall runtime of your
> code is very likely to end up dominated by I/O with the hard drive,
> not the microsecond differences in how you process each line.  The way
> to know for sure is to write code that is easy to read and does the
> correct thing.  Then run the code an see if it's too slow for your
> purposes.  If it is, profile the code and see where it's spending all
> of its time.  Only then can you actually optimize the right places.
>
> Once you've identified where your code needs to be faster, you're
> likely to get more mileage out of a clever algorithm change than a
> micro-optimization to your filtering. Or maybe you'll discover that it
> really is worthwhile to optimize your filtering, because it's inside a
> tight loop, and that's where all of your time is spent.  There are a
> lot of tricks you can use to slightly speed up your python code, but
> none of them are worth doing until you know for sure that you're
> optimizing in the right place.  And if it turns out that the code's
> runtime is fine as first written, you don't have to waste your time
> doing lots of work for little gain.
>
> --
> Jerry
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