Remove key/value pairs from a hash

[cajun]

I'm trying to remove key/value pairs from a hash. According to Q&A How do I completely remove a key/value pair from my hash?, the following code I believe should work, but it isn't. Apparently, I'm missing something here.

%hash1=("key1"=>"value1","key2"=>"value2", "key3"=>"value3", "key4"=>"
+value4", "key5"=>"value5");
@array=(key3, key4);

foreach (@array){
    delete($hash1{"$_"});
}

Thanks,
Mike

[ikegami]

Your code *does* work. What makes you think it doesn't?

<your code here>

require Data::Dumper;
print(Data::Dumper::Dumper(\%hash1));

__END__
output
======
$VAR1 = {
          'key5' => 'value5',
          'key2' => 'value2',
          'key1' => 'value1'
        };

Of course, you should quote key3 and key4 (it's good practice, and it's strict-friendly):
@array = ("key3", "key4");
or
@array = qw( key3 key4 );

And why use
"$_"
when you can simply use
$_

[Zaxo]

What doesn't work about it? If I add print keys %hash1; to the end of your code, it prints key5key2key1 What are you expecting?

[dReKurCe]

Greetings: The following code worked for me:

#! /usr/bin/perl

%hash1=("key1"=>"value1","key2"=>"value2", "key3"=>"value3", "key4"=>"
value4", "key5"=>"value5");
@array=(key3, key4);

foreach (@array){
    delete($hash1{"$_"});
    }

while (($key,$value)= each (%hash1)){
print "$key =$value\n"};

by producing


key5 =value5
key2 =value2
key1 =value1

[cajun]

Problem solved. It was so simple I'm embarrased to explain what happened. Yet perhaps someone who is searching for answers in the future, may stumble across this node and get some clues to their problem.

The short answer to the problem was to look at everything. Not just the piece of code you think isn't working.

Both %hash1 and @array are read in from a file. See where this is headed? I did a chomp when I was reading in the data for %hash1, but forgot to do a chomp when I was reading in the data for @array.

%key3\n ne %key3
%key4\n ne %key4

Thanks to all for the suggestions.
Mike

[cajun]

Thanks ikegami & Zaxo.

The reason I'm thinking it isn't working is if I print out %hash1 AFTER deleting the key/value pairs, it is the same size as it was before deleting the pairs.

I must have an issue elsewhere. Thanks for the help. I'll continue looking.
Mike

[ikegami]

I'm curious... What do you mean by the size of the hash? How do you obtain it?

[cajun]

Sorry, poor choice of words. The hash is written out to a file after the deletion of the records (key/value pairs). It has the same number of records (key/value pairs) after the deletion as it did before the deletion.

Thanks,
Mike

EDIT -


$before = keys %hash1;
$after = keys %hash1;

[ikegami]

It still works... $before is 5, $after is 3

Read more... (582 Bytes)

The problem is obviously not with delete, but with your data. Why don't you dump the array, the before-hash and the after-hash using Data::Dumper as shown in my first post. That will show the problem with your real data.