Frankenstring

[Andreas Lobinger]

Aloha,

Thomas Lotze wrote:
> I think I need an iterator over a string of characters pulling them out
> one by one, like a usual iterator over a str does. At the same time the
> thing should allow seeking and telling like a file-like object:
>>>>f = frankenstring("0123456789")
>>>>for c in f:
> ...     print c
> ...     if c == "2":
> ...         break
> ... 
> 0
> 1
> 2
>>>>f.tell()
> 3L
>>>>f.seek(7)
>>>>for c in f:
> ...     print c
> ... 
> 7
> 8
> 9
> I can think of more than one clumsy way to implement the desired
> behaviour in Python; I'd rather like to know whether there's an
> implementation somewhere that does it fast. (Yes, it's me and speed
> considerations again; this is for a tokenizer at the core of a library,
> and I'd really like it to be fast.) 

You can already think my answer, because i'm doing this
at the core of a similar library, but to give others
the chance to discuss.

 >>> f = "0123456789"
 >>> p = 0
 >>> t2 = f.find('2')+1
 >>> for c in f[p:t2]:
...  print c
...
0
1
2
 >>> p = 7
 >>> for c in f[p:]:
...  print c
...
7
8
9

A string, and a pointer on that string. If you give up the
boundary condition to tell backwards, you can start to eat up
the string via f = f[p:]. There was a performance difference
with that, in fact it was faster ~4% on a python2.2.

I dont't expect any iterator solution to be faster than
that.

Wishing a happy day
		LOBI