Re: Array to hash converstion

[quester]

You want to use the each function. See http://perldoc.perl.org/functions/each.html. (This was the second hit in a Google search for "perldoc print hash each".)

[davorg]

You want to use the each function.

I'm not sure I understand how "each" will solve this problem. I don't think that you do either, given that you haven't shown an example.

See http://perldoc.perl.org/functions/each.html. (This was the second hit in a Google search for "perldoc print hash each".)

That's nicely self-referential, isn't it? How do you expect someone to come up with a Google search term that includes the name of the function they're looking for?

[gem555]

The above code prints only one pair of values.

for my $data_pair (@data_list) {

print "$data_pair->{'key'},$data_pair->{'value'}\n";

}
correct,AAA
correction,BBB
date,20090303
date,20090308

These values and keys should be converted to hash map

[spazm]

I believe this is your question:

"I have an array (@data_list) containing hash references. Each hash reference contains two keys, 'key' and 'value'. I want to turn this into one hash containing 'key'=>'value' pairs. How can I do this?"

My solutions below assume that you have unique key values, or are un-interested in collisions. In the case of a collision, the last reference to the key wins.

Here is a fully verbose version:

my %final_hash;
foreach my $data_pair ( @data_list)
{
  $key   = $data_pair->{ key };
  $value = $data_pair->{value};
  $final_hash{ $key } = $value;
}

use Data::Dumper;
print Dumper \%final_hash;

A shorter version:

my %final_hash = 
  map { $_->{key} => $_->{value} } 
  @data_list;

#verify the output
use Data::Dumper;
print Dumper \%final_hash;

And how do we know they work? We test them.

Full version with tests:

#!/usr/bin/perl -w

use strict;
use Data::Dumper;
use Test::More tests => 2;

my @data_list = (
    { key => 'correct',    value => 'AAA' },
    { key => 'correction', value => 'BBB' },
    { key => 'date',       value => '20090303' },
    { key => 'date',       value => '20090308' },
);
my $expected = {
    correct    => 'AAA',
    correction => 'BBB',
    date       => '20090303',
    date       => '20090308',
};

my %final_hash_long;
foreach my $data_pair (@data_list) {
    my $key                = $data_pair->{key};
    my $value              = $data_pair->{value};
    $final_hash_long{$key} = $value;
}

my %final_hash_short =
  map { $_->{key} => $_->{value} } @data_list;

is_deeply( \%final_hash_long,  $expected, "long version works" );
is_deeply( \%final_hash_short, $expected, "short version works" );

[gem555]

#!/usr/bin/perl -w
use strict;

my @value_pairs = qw (one abc two xyz);
my %hash = @value_pairs;

foreach my $key (keys %hash)
{
   print "key $key is $hash{$key}\n";
}
__END__
prints:
key one is abc
key two is xyz
key one is def

If two keys are same then, output is

key one is abc
key two is xyz

so for the key one value is def is not printed here. The expected output is

key one is abc
key two is xyz
key one is def

Please tell me how can I get the output like this

[gem555]

#!/usr/bin/perl -w
use strict;
use warnings;

my @data_list = (
    {key => 'correct', value => 'Article_text1'},
    {key => 'correct', value => 'Article_text2'},
    {key => 'date', value => '2009-01-01'},
    {key => 'date', value => '2009-01-02'}
);


my @correct;
my @date;
for my $data_pair (@data_list) {
print "Value:$data_pair->{value}:Key:$data_pair->{key}\n";

if($data_pair->{key} eq 'correct'){
 @correct = $data_pair->{value};
}


if($data_pair->{key} eq 'date'){

 @date = $data_pair->{value};
}


}
print "The array is @correct\n";
print "The array is @date\n";

The array stores only the last value. How to store all the values into array