Sorting hash

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

Replies are listed 'Best First'.
Re: Sorting hash by stiller (Friar) on Feb 21, 2008 at 11:50 UTC
`use strict; use warnings; use Data::Dumper; # nice my @Data; # bad name, what does it store? while(<DATA>){ my($meth,$list,$count)= split ','; push @Data, { 'meth'=>$meth, 'list'=>$list, 'count'=>$count }; } print "Unsorted:\n", Dumper( @Data ), "\n"; @Data = sort { $a->{'meth'} cmp $b->{'meth'} } @Data; # swap $a and $b if you want the other direction print "Sorted:\n", Dumper( @Data ), "\n"; __DATA__ def,phyton\tjavascript,2 abc,perl\terlang\tlisp,1 ghi,arc\truby\tprolog,3` [download] also, avoid using $a and $b when not sorting. They will confuse you, because they are global. Not a problem in your code here though. hth Update: You had another question which I overlooked: the value you get, 2HASH(0x225e44), tells you that you have not a value, but a hash, which will have to be dereferenced to get at whatever is in the hash, for example using the keys function: `my %dd; $dd{'1'}{'2'}{'3'}="hi"; $dd{'1'}{'3'}{'5'}="hello"; print "\nkeys in hash: ", join ' ', keys %{ $dd{'1'} };` [download]	[reply] [d/l] [select]
Re^2: Sorting hash by vsailas (Beadle) on Feb 21, 2008 at 12:05 UTC
Thank you, you made my day!	[reply]
Re: Sorting hash by johngg (Canon) on Feb 21, 2008 at 11:53 UTC
Firstly, you should avoid using the scalars `$a` and `$b` as they are special and are reserved for use with sort. Secondly, you should consider whether you want to remove the line terminator before doing your `split`; if you do, look at chomp. Remember that each element you are passing into the sort routine is a hash reference so you have to de-reference to get to the element you want to sort by. This should do what you want. `my @Data = (); while ( <FH> ) { chomp; my ( $meth, $list, $count ) = split m{,}; push @Data, { meth => $meth, list => $list, count => $count, }; } @sortedData = sort { $a->{ meth } cmp $b->{ meth } } @Data;` [download] I hope this is useful. Cheers, JohnGG	[reply] [d/l] [select]
Re: Sorting hash by Punitha (Priest) on Feb 21, 2008 at 11:59 UTC
Hi vsailas, You can try like this by modifying your array(@Data) to little bit as, `use strict; my @Data; while(<DATA>){ chomp($_); my($string,$listref,$count)= split(',' , $_); push(@Data,[$string,$listref,$count]); } print "METH:$_->[0]\tREF:$_->[1]\tCOUN:$_->[2]\n" for sort {$a->[0] cm +p $b->[0]} @Data;` [download] `__DATA__ meth2, \@array1, 3 meth3, \@array2, 36 meth1, \@array3, 8 meth5, \@array4, 10` [download] Punitha	[reply] [d/l] [select]
Re: Sorting hash by nikhil.patil (Sexton) on Feb 21, 2008 at 11:39 UTC
You can use the Tie::Hash::Sorted module. This module presents hashes in sorted order. Alternatively, you can also use the Tie::IxHash module and add the elements into the hash in ascending order of $a. Tie::IxHash module implements hashes that preserve the order in which the hash elements were added into the hash.	[reply]
Re^2: Sorting hash by johngg (Canon) on Feb 21, 2008 at 11:58 UTC
I think the thread title is misleading, the OP is actually trying to sort an array of hashes by one of the hash elements. Cheers, JohnGG	[reply]
Re: Sorting hash by hipowls (Curate) on Feb 21, 2008 at 19:37 UTC
To answer your second question `$dd{'1'}{'2'}{'3'}="hi";` [download] is equivalent to `my %dd = ( 1 => { 2 => { 3 => 'hi' } } );` [download] and `%{$dd{'1'}}` is equal to `( 2 => { 3 => 'hi' } )`. To get the value you assign it to a scalar and then dereference the keys of that hash ref. `my $hash_ref1 = $dd{1}; print $hash_ref->{2}{3}, "\n"; # prints h1` [download] or if you are iterating over a structure `while ( my ( $key, $hash_ref ) = each ( %{ $dd{1} } ) { # $key == 2 # $hash_ref == { 2 => { 3 => 'hi' } } }` [download]	[reply] [d/l] [select]