How can I parse this without regex? - regex

Question

A friend of mine said if the regex I'm using is too long, it's probably the wrong tool for the job. Any thoughts here on a better way to parse this text? I have a regex that returns everything to an array I can easily just chunk out, but if there's another simpler way I'd really like to see it.
Here's what it looks like:
2 AB 123A 01JAN M ABCDEF AA1 100A 200A 02JAN T /ABCD /E
Here's a break down of that:
2 is the line number, these range from 1 all the way to 99. If you can't see because of formatting, there is a space charecter prepending numbers less than 10.
The space may or may not be replaced by an *
AB is an important unit of data (UOD).
AB may be prepended by /CD which is another important UOD.
123 is an important UOD. It can range from 1 (prepended by 4 spaces) to 99999.
A is an important UOD.
01JAN is a day/month combination, I need to extract both UODs.
M is a day name short form. This may be a number between 1 and 7.
ABC is an important UOD.
DEF is an important UOD.
The space after DEF may be an *
AA1 may be zero characters, or it may be 5. It is unimportant.
100A is a timestamp, but may be in the format 1300. The A may be N when the time is 1200 or P for times in the PM.
We then see another timestamp.
The next date part may not be there, for example, this is valid:
93*DE/QQ51234 30APR J QWERTY*QQ0 1250 0520 /ABCD*ASDFAS /E
The data where /ABCD*ASDFAS /E appears is irrelevant to the application, but, this is where the second date stamp may appear. The front-slash may be something else (such as a letter).
Note:
It is not space delimited, some parts of the body run into others. Character position is only accurate for the first two or three items on the list
I don't think I left anything out, but, if there's an easier way to parse out a string like this than writing a regex, please let me know.

Answer 1

This is a perfect task for regular expressions. The text does not contain nesting and the items you're matching are fairly simple taken individually.
Most regular expression syntaxes have an xtended flag or mode that allows whitespace and comments to improve readability. For example:
$regex = '#
# 2 is the line number, these range from 1 all the way to 99.
# There is a space character prepending numbers less than 10.
# The space may or may not be replaced by an *.
[ *]\d|\d\d
\s
# AB is an important unit of data (UOD).
# AB may be prepended by /CD which is another important UOD.
(/CD)?AB
\s
# 123 is an important UOD. It can range from 1 (prepended by 4 spaces)
# to 99999.
\s{4}\d{1}|\s{3}\d{2}|\s{2}\d{3}|\s{1}\d{4}|\d{5}
#x';
And so on.

Answer 2

A regex seems fine for this application, but for simplicity and readability, you might want to split this into several regexes (one for each field) so people can more easily follow which part of the regex corresponds to which variable.

Answer 3

You can always code your own parser by hand, but that would be more lines of code than a regex. The lines of code, however, will probably be simpler to follow for the reader.

Answer 4

Simply write a custom parser that handles it line by line. It seems like everything is at a fixed position rather than space/comma-delimited, so simply use those as indices into what you need:
line_number = int(line_text[0:1])
ab_unit = line_text[3:4]
...
If it is indeed space-delimited, simply split() each line and then parse through each, splitting each chunk into component parts where appropriate.