Browsing text ; Python the right tool?

[Paul Kooistra]

I need a tool to browse text files with a size of 10-20 Mb. These
files have a fixed record length of 800 bytes (CR/LF), and containt
records used to create printed pages by an external company.

Each line (record) contains an 2-character identifier, like 'A0' or
'C1'. The identifier identifies the record format for the line,
thereby allowing different record formats to be used in a textfile.
For example:

An A0 record may consist of:
recordnumber [1:4]
name         [5:25]
filler       [26:800]

while a C1 record consists of:
recordnumber [1:4]
phonenumber  [5:15]
zipcode      [16:20]
filler       [21:800]

As you see, all records have a fixed column format. I would like to
build a utility which allows me (in a windows environment) to open a
textfile and browse through the records (ideally with a search
option), where each recordtype is displayed according to its
recordformat ('Attributename: Value' format). This would mean that
browsing from a A0 to C1 record results in a different list of
attributes + values on the screen, allowing me to analyze the data
generated a lot easier then I do now, browsing in a text editor with a
stack of printed record formats at hand.

This is of course quite a common way of encoding data in textfiles.
I've tried to find a generic text-based browser which allows me to do
just this, but cannot find anything. Enter Python; I know the language
by name, I know it handles text just fine, but I am not really
interested in learning Python just now, I just need a tool to do what
I want.

What I would REALLY like is way to define standard record formats in a
separate definition, like:
- defining a common record length; 
- defining the different record formats (attributes, position of the
line);
- and defining when a specific record format is to be used, dependent
on 1 or more identifiers in the record.

I CAN probably build something from scratch, but if I can (re)use
something that already exists it would be so much better and faster...
And a utility to do what I just described would be REALLY usefull in
LOTS of environments.

This means I have the following questions:

1. Does anybody now of a generic tool (not necessarily Python based)
that does the job I've outlined?
2. If not, is there some framework or widget in Python I can adapt to
do what I want?
3. If not, should I consider building all this just from scratch in
Python - which would probably mean not only learning Python, but some
other GUI related modules?
4. Or should I forget about Python and build someting in another
environment?

Any help would be appreciated.