[Tutor] Pythonic way of concatenation of elements in an array

[Blockheads Oi Oi]

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.