Parsing a file with iterators

[Luis Zarrabeitia]

I need to parse a file, text file. The format is something like that:

TYPE1 metadata
data line 1
data line 2
...
data line N
TYPE2 metadata
data line 1
...
TYPE3 metadata
...

And so on. The type and metadata determine how to parse the following data
lines. When the parser fails to parse one of the lines, the next parser is
chosen (or if there is no 'TYPE metadata' line there, an exception is thrown).

This doesn't work:

===
for line in input:
    parser = parser_from_string(line)
    parser(input)
===

because when the parser iterates over the input, it can't know that it finished
processing the section until it reads the next "TYPE" line (actually, until it
reads the first line that it cannot parse, which if everything went well, should
be the 'TYPE'), but once it reads it, it is no longer available to the outer
loop. I wouldn't like to leak the internals of the parsers to the outside.

What could I do?
(to the curious: the format is a dialect of the E00 used in GIS)
 
-- 
Luis Zarrabeitia
Facultad de Matemática y Computación, UH
http://profesores.matcom.uh.cu/~kyrie