CODEWITHSUNDEEP
perl
viswa
viswa

Reputation: 61

numbers of keys in a hash

I am trying to find out the number of keys and number of values in a hash and print those numbers. I've written my code like this but it has not given the number of keys. What is the error in my code?

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

use XML::LibXML::Reader;
my $file;open $file, 'formal.xml');
my $reader = XML::LibXML::Reader->new( IO => $file ) or die ("unable to open file");

while ( $reader->nextElement( 'DATA' ) ) {
    my $info = $reader->readOuterXml();
    $reader->nextElement( 'Number' ); 
    my $number = $reader->readInnerXml(); 
    print( "num: $number\n" );
    print( " datainfo: $info\n" );

How can I store these num and datainfo in a hash? And how can I count number of keys in hash? I tried like this but it is not working.

my %nums =( "$number", $info);

while ((my $keys, my $values) = each (%nums)) { 
    print ("NUMBER:$keys." =>"INFORMATION: ".$values." \n");
}

my $key_count = keys %nums;
print "$key_count";
} 
close($file);
}

When I am trying to execute it, it gives only one number, but I have more numbers. Maybe my hash contains one number, but how can I iterate my hash to store more numbers?

Upvotes: 2

Views: 9092

Answers (3)

DavidRR
DavidRR

Reputation: 19427

Goal: I am trying to find out numbers keys and number of values in hash.

Here is a direct answer to this question in general.

To obtain the number of keys in your hash, apply the keys function in a scalar context:

scalar keys %my_hash
# -or-
my $number_of_keys = keys %my_hash;

The number of values will be identical (although one or more values may be undefined). You can prove this by applying the values function in a similar fashion:

scalar values %my_hash
# -or-
my $number_of_values = values %my_hash;

Upvotes: 1

MisterEd
MisterEd

Reputation: 1735

keys() and values() both return arrays. When referenced in scalar context, arrays in Perl return the size of the array. So, to get the number of keys or values in your hash, just reference the result of keys() or values() in scalar context:

# prints the number of keys
print( scalar(keys(%hash)), "\n" );
print( keys(%hash) . "\n" );

# prints the number of values
print( scalar(values(%hash)), "\n" );
print( values(%hash) . "\n");

Using your %nums array:

my %nums = ( $number, $info );
print( "number of keys: ", scalar(keys(%nums)), "\n" ); # will print `1'

Note that your %nums hash has only one key-value pair with $number as the key and $info as the value. (A more conventional and readable way to declare %nums would be my %nums = ( $number => $info ); )

Upvotes: 7

Andrey
Andrey

Reputation: 1818

try

my %nums;
while ( $reader->nextElement( 'DATA' ) ) {     
   my $info = $reader->readOuterXml();     
   $reader->nextElement( 'number' );      
   my $number = $reader->readInnerXml();  
   $nums{$number} = $info;    
   print( "num: $number\n" );    
   print( " datainfo: $info\n" ); 
}

and remove my %nums =( "$number", $info);

When you do your while loop, your $number and $info overwrite themselves each time. So you need to store that data in the hash in the while loop.

Upvotes: 2

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