carol.j has asked for the wisdom of the Perl Monks concerning the following question:

How to use perl to parsing a XML file to csv file which have the same sequence in xml file? The following XML file called booklist.xml, in example:

 
   <book>
      <author>Book 1 author 1</author>
      <author>Book 1 author 2</author>
      <title>Book 1 title</title>
      <isbn>Book1ISBN</isbn>
   </book>

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Example of Converting from XML to a Perl hash record

 #!/usr/bin/perl

# Script to illustrate how to parse a simple XML file
# and dump its contents in a Perl hash record.

use strict;
use XML::Simple;
use Data::Dumper;

my $booklist = XMLin('booklist.xml');

print Dumper($booklist);

[download]

Running this script outputs the following: 

$VAR1 = {
          'book' => {
                      'isbn' => 'Book1ISBN',
                      'title' => 'Book 1 title',
                      'author' => [
                                  'Book 1 author 1',
                                  'Book 1 author 2'
                                ]
                    }

        }

[download]

But hope we can get the sequence like this: 

$VAR1 = {
          'book' => {
                      'author' => [
                                  'Book 1 author 1',
                                  'Book 1 author 2'
                                ]
                       'title' => 'Book 1 title',
                       'isbn' => 'Book1ISBN',
                                                              }

        }

[download]
  • Comment on How to use perl to parsing a XML file to csv file which have the same sequence in xml file?
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Re: How to use perl to parsing a XML file to csv file which have the same sequence in xml file?
by tobyink (Canon) on Jun 14, 2012 at 12:01 UTC

    In you care about the order of those elements XML::Simple (or indeed any similar XML-to-hashref tool) is not your friend. Perl hashes do not preserve order. There are modules that give you order-preserving hashes (via ties) but persuading XML::Simple to use them is probably not possible.

    use PerlX::MethodCallWithBlock;
use Text::CSV;
use XML::LibXML 1.94;

local $\ = "\n";
my $xml  = XML::LibXML->load_xml(IO => \*DATA);
my $csv  = Text::CSV->new;

foreach my $book ($xml->findnodes('/library/book'))
{
    my $row = $book->findnodes('./*')->map{ $_->textContent };
    $csv->print(\*STDOUT, $row);
}

__DATA__
<library>
    <book>
        <author>Book 1 author 1</author>
        <author>Book 1 author 2</author>
        <title>Book 1 title</title>
        <isbn>Book1ISBN</isbn>
    </book>
    <book>
        <author>Book 2 author 1</author>
        <author>Book 2 author 2</author>
        <title>Book 2 title</title>
        <isbn>Book2ISBN</isbn>
    </book>
</library>

    [download]

    The output from the above is:

    "Book 1 author 1","Book 1 author 2","Book 1 title",Book1ISBN
"Book 2 author 1","Book 2 author 2","Book 2 title",Book2ISBN
    perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
[reply]
[d/l]
      Hello

      I tried to run the example provided here, and I get the following error:

       Expected fields to be an array ref at xml.pl line 11

      When I look at the contents of $book, I see: 

      $VAR1 = bless( [
                 'Book 1 author 1',
                 'Book 1 author 2',
                 'Book 1 title',
                 'Book1ISBN'
               ], 'XML::LibXML::NodeList' );

$VAR1 = bless( [
                 'Book 2 author 1',
                 'Book 2 author 2',
                 'Book 2 title',
                 'Book2ISBN'
               ], 'XML::LibXML::NodeList' );

      [download]
      I am running perl 5.10.1 -- any tips?
[reply]
[d/l]
[select]

        It worked on my machine, but Text::CSV's behaviour can be a little variable - it has two underlying implementations: one in pure Perl, and a faster one in C. Which one you get is the luck of the draw. In this case, $row is a blessed arrayref; Text::CSV expects an arrayref; it looks like one of the implementations rejects the arrayref if it's blessed but the other does not.

        $csv->print(\*STDOUT, [@$row]);  # unblessed shallow clone of $row

        [download]
        perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
[reply]
[d/l]
[select]

        I am running perl 5.10.1 -- any tips?

        Forget it, its magic :) I get 

        PL_linestr not long enough, was Devel::Declare loaded soon enough in f
+udge at PerlX/MethodCallWithBlock.pm line 107.

        [download]

        Report it to PerlX::MethodCallWithBlock maintainer

[reply]
[d/l]
Re: How to use perl to parsing a XML file to csv file which have the same sequence in xml file?
by Utilitarian (Vicar) on Jun 14, 2012 at 10:48 UTC
    Could you give us an example record of the csv file you wish to output?

    print "Good ",qw(night morning afternoon evening)[(localtime)[2]/6]," fellow monks."
[reply]
[d/l]
Re: How to use perl to parsing a XML file to csv file which have the same sequence in xml file?
by Anonymous Monk on Jun 14, 2012 at 10:31 UTC

    Running this script outputs the following: ... But hope we can get the sequence like this: ...

    Those two are identical data structures

[reply]

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