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easiest way to print the content of a hash?

by s_m_b (Acolyte)
on Jul 13, 2006 at 15:32 UTC ( #560981=perlquestion: print w/ replies, xml ) Need Help??
s_m_b has asked for the wisdom of the Perl Monks concerning the following question:

I need to check the current content of a hash, but can't figure how to just dump the content out - similar to doing print @some_list for dumping out a list's content. I tried %some_hash and %some_hash{} with no success.

Comment on easiest way to print the content of a hash?
Re: easiest way to print the content of a hash?
by ptum (Priest) on Jul 13, 2006 at 15:33 UTC

    There's always Data::Dumper.

    Or, assuming your hash values are scalars, you can step through the keys and print out the contents, like this:

    foreach (sort keys %myhash) { print "$_ : $myhash{$_}\n"; }

    No good deed goes unpunished. -- (attributed to) Oscar Wilde
      I can never quite get why nobody (apart from me) ever seems to recommend Data::Dumper::Simple for debugging?

      It's way easier to use than Data::Dumper, especially for more complex data structures. There is no need to pass references, and the output contains the actual variable names - instead of "VAR1", "VAR2", etc.
      I know you can get the same thing with Data::Dumper using Dumper->Dump, but this can very quickly become quite unwieldy.

      About the only objection I could imagine to using Data::Dumper::Simple is that is uses source filters, but if you're only using it for debugging - and not in production code - what's the problem?

      Just curious....
      Darren :)

        Perhaps because it's a source filter? (Yes, I read your post. And yes, that's my reason.)

        Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
        How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart
        There is no need to pass references, and the output contains the actual variable names - instead of "VAR1", "VAR2", etc.
        it's time again to quote my .vimrc:
        :imap dumper <ESC>^iwarn Data::Dumper->Dump([\<ESC>llyw$a], ['<ESC>pa']);<ESC>
        let's you type '@myarraydumper' and you'll get
        warn Data::Dumper->Dump([\@myarray], ['myarray']);

        Data::Dumper is in the core, and with the help of my editor i don't have to type much to get a decent debugging output.

      use Data::Dumper; my %hash = ( key1 => 'value1', key2 => 'value2' ); print Dumper(%hash); # okay, but not great print "or\n"; print Dumper(\%hash); # much better
      And the output:
      $VAR1 = 'key2'; $VAR2 = 'value2'; $VAR3 = 'key1'; $VAR4 = 'value1'; or $VAR1 = { 'key2' => 'value2', 'key1' => 'value1' };
Re: easiest way to print the content of a hash?
by marto (Chancellor) on Jul 13, 2006 at 15:38 UTC
      thanks for the suggestions. data::dumper looks good to me. I've used the foreach, of course, but that's messy for a quick output.
Re: easiest way to print the content of a hash?
by coreolyn (Parson) on Jul 13, 2006 at 17:32 UTC

    If you're just doing a quick check on the contents of a hash nothing beats print "\%hash = @{[%hash]}\n"; for debugging.

Re: easiest way to print the content of a hash?
by davido (Archbishop) on Jul 13, 2006 at 17:39 UTC

    If you don't like the output of Data::Dumper and just want a simple key/value dump (without any deep datastructure exploration), you could apply this function:

    sub print_hash { my $href = shift; print "$_\t=> $href->{$_}\n" for keys %{$href}; }

    It could also be written like this:

    sub print_hash { my $href = shift; while( my( $key, $val ) = each %{$href} ) { print "$key\t=>$val\n"; } }

    Dave

Re: easiest way to print the content of a hash?
by planetscape (Canon) on Jul 17, 2006 at 06:20 UTC

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