Extracting values from text file

[Mirco Wahab]

Thus spoke Preben Randhol (on 2006-06-16 10:36):

> A short newbie question. I would like to extract some values from a
> given text file directly into python variables. Can this be done simply
> by either standard library or other libraries? Some pointers where to
> get started would be much appreciated.

I used your example just to try that in python
(i have to improve my python skills), but waved
the white flag after realizing that there's no
easy string/var-into-string interpolation.

I tried to build some parser table
which will then translate hings into a dictionary

  v_apples = '\b\S+';
  v_ducks  = '\b\S+';
  v_butter = '\b\S+';

  rg_ar = [ "Apples (v_apples)" ,
            "(v_ducks) Ducks"   ,
            "(v_butter) butter" ]

the above interpolation won't work, so I gave up.

To give an idea what I intended, I'll add
the short perl script which I took as a
blue print for my python effort (your
example text may be used):


   my @filter = (                 # define filter table
     "Apples (apples)",
     "(ducks) Ducks",
     "(butter) g butter",
   );
   my %varname = ();              # variable names will be found in text
   my $example = do { local$/; <DATA> }; # read the appended example text
                                         # change <DATA> to <> for std input

   for (@filter) {                       # iterate over filter rules
       if( s/\((.+)\)/\\b(\\S+?)\\b/ ) { # pull out variable names ($1)
           my $v = $1;                   # and replace them by '\b(\S)\b'
           $varname{$v} = $1 if $example =~ /$_/;      # pull values from
       }                                               # text to varnames
   }


your text prints then:
 (for (keys %varname) { print "$_\t=>\t$varname{$_}\n"; })

   apples => 34
   butter => 0.5
   ducks  => 56

with variable names taken from your text:

  __DATA__
  An example text file:
  -----------
  Some text that can span some lines.
    Apples 34
    56 Ducks
  Some more text.
    0.5 g butter
  -----------------

Above will do the job in perl, but I have no idea
how to translate this to python, especially, as I
said, the string-to-string interpolation thing for
the build-up regex.

Maybe some experts may help out?

Regards

Mirco