On 27/01/2012 06:44, Andre' Walker-Loud wrote:
Hi Steven,
(5) When assembling strings from substrings, never use repeated concatenation
using + as that can be EXTREMELY slow. Use str.join to build the string in one
assignment, instead of multiple assignments.
Your code shown above is *very* inefficient and will be PAINFULLY slow if m is
very large. To understand why, you should read this article:
http://www.joelonsoftware.com/articles/fog0000000319.html
In this case, you can replace your snippet with this:
result = '-'.join(str(item) for item in m[1:])
This was an interesting article. I have only had one programming class, and
that was 15 years ago or so, so these are not issues I am aware of.
I often find myself joining strings (and have mostly used + to do it). An
alternate method I use is, for eg.
print('here is a string %s which has many variables %s %s %s I have to sort
out' %(s1,s2,s3,s4))
where the various strings (s1 - s4) have been determined elsewhere, perhaps in
a loop.
Is this method any better at combining strings than the +? My first guess
would be no, but that is really just a guess.
Thanks,
Andre
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You might like to take a look here
http://wiki.python.org/moin/PythonSpeed/PerformanceTips#String_Concatenation
--
Cheers.
Mark Lawrence.
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