A Problem With Hashes and Keys

bivouac has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks - I'm having a problem with a another problem that I experienced before. I have three different text files. One is a master file, one is a delete file and another is a add file. I need to remove the contents of the deleted file from the master file and add the contents of the add file to the new master file. I figured this would be fairly trivial given what I learned from my previous problem and yet I can't get this to work.

#!/usr/bin/perl -w

use strict;

my $dir = "/foo/";

my $raw_file = $dir."sample_qw_zips.txt";
my $delete_file = $dir."sample_qw_deletes.txt";
my $add_file = $dir."dsl_capable_add_0615.txt";

my %delete = ();

open (DELETE_FILE, "< $delete_file")
    or die "Can't open $delete_file: $!\n";

open (RAW_FILE, "< $raw_file")
    or die "Can't open $raw_file: $!\n";

open (OUTPUT, "> output.txt")
    or die "Can't open OUTPUT: $!\n";

#populate delete hash 
while (my $deleted_zip = <DELETE_FILE>) {
    chomp $deleted_zip;
    $delete{$deleted_zip} = 1;
}

while (my $raw_zip = <RAW_FILE>) {
    chomp $raw_zip;
    # strings in a weird place in a weird place
    my $zip = substr($raw_zip, 3, 9);
    # maybe use an unless statement
    if (exists $delete{$zip}) {
        # don't do anything
    } else {
        print OUTPUT $raw_zip, "\n";
    }
}

close DELETE_FILE;
close RAW_FILE;    
close OUTPUT;
[download]

You'd think after all these years I would be more comfrtable with hashes. Nope. Thanks.

Comment on A Problem With Hashes and Keys Download Code

Replies are listed 'Best First'.
Re: A Problem With Hashes and Keys by Grygonos (Chaplain) on Jul 19, 2004 at 14:24 UTC
You want something like Tie::File. This would allow you to edit the master file in place (unless that's a problem) Also it seems like you only need an array, as there is no association to be made (ie all it seems you are populating is that a hash key hashes to one when it needs to be deleted. You would be better off doing something like this `open(DELETE,$file) or die "$!"; my @delete = <DELETE>; chomp for(@delete); close(DELETE); open(MASTER,$file) or die "$!"; open(OUTPUT,$file) or die "$!"; while(<MASTER>) { my $zip = substr($_, 3, 9); if(!deletable(\$zip,\@delete)) { print OUTPUT, $zip; } } close(OUTPUT); close(MATSER); sub deletable { my ($item,$list) = @_; my $rv = 0; foreach(@{$item}) { if($$item eq $_) { $rv = 1; last; } } return $rv; }` [download] that's untested but its how i see it working best...Tie::File is a good option.. but if you're wanting to keep the same format.. this should work. This is all assuming that your delete file isn't ginormous. Grygonos	[reply] [d/l]
Re: A Problem With Hashes and Keys by eXile (Priest) on Jul 19, 2004 at 14:11 UTC
your code works pretty well on my machine. I used the next filecontent for a test: input: `CA 92037 CA 92021 CA 92055 CA 92037` [download] delete: `92037 92055` [download] And this gave me the output: `CA 92021` [download] Maybe something wrong with your input-file format?	[reply] [d/l] [select]
Re^2: A Problem With Hashes and Keys by bivouac (Beadle) on Jul 19, 2004 at 14:54 UTC
Is it possible that my substr call is hosing everything up? When I removed that from the code that seemed to work great - but by removing the substr call I need to adjust the incoming data which isn't a good thing. Still confused as heck.	[reply]
Re^3: A Problem With Hashes and Keys by ccn (Vicar) on Jul 19, 2004 at 15:01 UTC
Just make shure that your `substr` produces the same values what are stored in DELETE_FILE	[reply] [d/l]
Re: A Problem With Hashes and Keys by meredith (Friar) on Jul 19, 2004 at 14:16 UTC
I'm really not sure if you asked a question or not. =) I noticed that you don't appear to be using your $add_file at all in the code, too. Anyway, a technique that seems to be more sane to me is one where you: Read/parse $raw_zip, and populate a %master hash. In a while loop reading from $delete_file, check if the key (in %master) for each line exists, and delete that key. Do similar for $add_file, adding entries to %master as requested. Finally, walk back over the %master hash, and output back to your original file. How does that sound to you? Update: I saw that file format for the "master" file. I would populate it like so, if you do something like I said above: `my ($state, $zip) = split; $master{$zip} = $state;` [download] I am assuming that there won't be any duplicate lines in your file, also. `mhoward - at - hattmoward.org`	[reply] [d/l]