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

[Alan Gauld]

On 27/01/12 06:44, Andre' Walker-Loud wrote:
> ...  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).

String addition is OK in some languages, or at least better than in 
Python so it is not a universal rule of programming. In Python the big 
problem is that each addition operation creates a new string so Python 
spends a lot of time allocating bigger and bigger chunks of memory only 
to throw it away again.

>> print('here is a string %s which has many variables %s %s %s I have to sort out' %(s1,s2,s3,s4))
> ...
> Is this method any better at combining strings than the +?

It is quite a bit better because Python can pre-calculate how much 
memory is needed and do it once.

However, I wouldn't get too stressed on speed. String formatting has a 
lot of other advantages over join() and is fast enough most of the time.
I tend to use formatting more than join() in my own code, but join() is 
best if you are building up a string in a loop say. You can append the 
substrings to a list and then join the list at the end.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/