[Tutor] Avoiding repetetive pattern match in re module

[Danny Yoo]

> >From a technical standpoint, it has "quadratic" complexity in terms of
> what work the computer is doing.  It's related to the mathematical idea
> that 1 + 2 + 3 + 4 + ... + n = n(n+1).
>
>     http://en.wikipedia.org/wiki/Triangle_number


Gaa, where did my division sign go?  *grin*

Sorry, that equation should be:

    1 + 2 + ... + n = n(n+1)/2

We can see this:

###############################################
>>> import operator
>>> def sumUpTo(n):
...     return reduce(operator.add, range(n+1))
...
>>> for i in range(10):
...     print sumUpTo(i), 'vs', i*(i+1) / 2
...
0 vs 0
1 vs 1
3 vs 3
6 vs 6
10 vs 10
15 vs 15
21 vs 21
28 vs 28
36 vs 36
45 vs 45
###############################################



> If you do end up having to concatenate a lot of strings together, use the
> join() method of lists instead.

I should clarify this.  I meant to say we should use the string method of
join() on lists.  For example, if we didn't have file1.read(), we could
still do:

###
ans = ''.join(file1.readlines())
###

which takes the lines of the file and joins them altogether at once.


Good luck!