Re: Creating a Multi Level Hash from CSV

Something like this? I faked an input file because you did not include a valid input file.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11132513
use warnings;

my %hash;

while( <DATA> )
  {
  my ( $top, @rest ) = split /,|\n/; # FIXME faking CSV for testing
  $hash{$top} = chain(@rest);
  }
use Data::Dump 'dd'; dd \%hash;

sub chain { return @_ > 1 ? { shift() => chain(@_) } : shift(); }

__DATA__
a,b,c,d,e
f,g,h,i,j
xx,yy,zz
this,is,a,strange,type,of,data,organization
[download]

Outputs:

{
  a => { b => { c => { d => "e" } } },
  f => { g => { h => { i => "j" } } },
  this => {
    is => {
            a => { strange => { type => { of => { data => "organizatio
+n" } } } },
          },
  },
  xx => { yy => "zz" },
}
[download]

Comment on Re: Creating a Multi Level Hash from CSV Select or Download Code

Replies are listed 'Best First'.
Re^2: Creating a Multi Level Hash from CSV by Fletch (Bishop) on May 14, 2021 at 12:43 UTC
Or you could do it functionally rather than explicit recursion using List::Util's `reduce` (not that that's likely to be of any help to trolls who're unfamiliar with a bog simple recursive sub . . .). `## (reduce #(hash-map %2 %1) 1 (reverse [:foo :bar :baz :quux])) use List::Util qw( reduce ); use Data::Dumper qw( Dumper ); my $hash = reduce { +{ $b => $a } } 1, reverse( qw( foo bar baz quux ) + ); say Dumper( $hash ); __END__ $VAR1 = { 'foo' => { 'bar' => { 'baz' => { 'quux' => '1' } } } };` [download] The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l] [select]
Re^2: Creating a Multi Level Hash from CSV by workInProgress12 (Novice) on May 13, 2021 at 17:18 UTC
This was so helpful, thank you so much I've really been struggling. I was wondering if you could explain the sub chain{} function? I'm not at all sure what you're doing there, but it works! Also do you have any advice as to what I should do if I want to remove the first row so the header doesn't do what the rest of the hash is doing. Again, really appreciate all your help.	[reply]
Re^3: Creating a Multi Level Hash from CSV by AnomalousMonk (Archbishop) on May 13, 2021 at 20:02 UTC
... explain the sub chain{} function ... The"Perl Magick" here is recursion; it is not peculiar to Perl in any way. `sub chain { return @_ > 1 ? { shift() => chain(@_) } : shift(); }` [download] If there are two or more items in the `@_` function argument array (`@_ > 1`), `{ shift() => chain(@_) }` executes. shift takes the top argument off of `@_` and makes it a hash key with the value of whatever the call to `chain(@_)` returns. Note that `chain(@_)` is called with whatever remains in the `@_` array after one item has been removed by the `shift` call. This key/value pair is then returned within an anonymous hash reference. If there are fewer than two items in the `@_` array, the call to `chain(@_)` simply returns the top item in the array. Note that this does not "properly" handle the case in which the `@_` array is empty. What is "proper" handling in this case (if it can even arise)? Only you can figure this out. `Win8 Strawberry 5.8.9.5 (32) Thu 05/13/2021 15:26:20 C:\@Work\Perl\monks >perl -Mstrict -Mwarnings my %hash; # my ( $top, @rest ) = split /,\|\n/; # FIXME faking CSV for testing my ($top, @rest) = qw(foo); $hash{$top} = chain(@rest); use Data::Dump 'dd'; dd \%hash; sub chain { return @_ > 1 ? { shift() => chain(@_) } : shift(); } ^Z { foo => undef }` [download] ... remove the first row so the header doesn't do what the rest of the hash is doing. One might do the following: `open(my $input, '<:utf8',"input.csv") or die;` `<$input>; # read and discard one line/record` (I think Text::CSV can do this for you (it does just about everything else :), but you'll have to check for yourself.) Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
A reply falls below the community's threshold of quality. You may see it by logging in.