[Baypiggies] string question

[Tim Hatch]

On 4/5/11 1:39 PM, Simeon Franklin wrote:
> On Tue, Apr 5, 2011 at 1:25 PM, Vikram K <kpguy1975 at gmail.com
> <mailto:kpguy1975 at gmail.com>> wrote:
> 
>     Given a string and some indices, how do i change upper characters
>     corresponding to some position(s) in the string to lower characters?
>     I tried and failed.

Your way is reasonable.  Depending on how sparse your modifications are,
you could also build up the string another way using slicing -- the core
of my suggestion is

>>> x = 'EPSPVRYDNLSR'
>>> x[:5]+x[5:7].lower()+x[7:]
'EPSPVryDNLSR'

But you'd want to build it up in a list or use cStringIO, like

>>> buf = []
>>> buf.append(x[:5])
>>> buf.append(x[5:7].lower())
>>> buf.append(x[7:])
>>> ''.join(buf)
'EPSPVryDNLSR'

And adapting for your method of indexing might be interesting.  If you
have start-stop positions that are non-overlapping and half-open, this
could be as easy as (completely untested):

prev_end = 0
end = len(x)
for start, end in index_pairs:
    if prev_end != start:
        buf.append(x[prev_end:start])
    buf.append(x[start:end].lower())
    prev_end = end
buf.append(x[end:])

Tim