Perl:With Text :: CSV可以写出一个哈希ref吗? [英] Perl: With Text::CSV can I write out a hash ref?
问题描述
我有一个Perl脚本,读取CSV文件,更改原始的列名称,添加新的(输出CSV列名存储在数组,header_line),为每一行读取添加新的字段值,然后写出一个新的CSV文件。
I have a Perl script that reads in a CSV file, changes the columns names of the original, adds new ones (output CSV column names are stored in the array, header_line), adds new field values for each row read, and then writes out a new CSV file.
感谢@harleypig对我最后的问题,我想使用:
Thanks to a comment by @harleypig on my last question, I'd like to use:
$csv_i->column_names( @header_line);
$row = $csv_i->getline_hr($fh_i)
使用有意义的名称而不是魔术数字轻松访问行字段。例如:
because this lets me easily access row fields using meaningful names rather than magic numbers. For example:
$row->{ 'name' } = get_fullname($row->{ 'name' });
现在唯一的问题是,写出行的最好方法是什么?以前,我使用了:
The only problem now is, what's the best way to write out the line? Previously, I used:
$csv_o->print( $fh_o, $row );
但是失败是因为它需要一个数组引用。如何使用csv_o对象写出散列引用?
But that fails because it expects an array ref. How do I write out the hash ref using the csv_o object?
推荐答案
使用散列片:
$csv_o->print( $fh_o, [ @$row{@header_line} ] );
map
切片更快:
use Benchmark 'cmpthese';
my @header_line = qw(a b c d e f g);
my $row = { map { $_ => $_ } @header_line };
my $array;
cmpthese(-3, {
slice => sub {
$array = [ @$row{@header_line} ];
},
map => sub {
$array = [ map { $row->{$_} } @header_line ];
},
});
给我:
Rate map slice
map 282855/s -- -42%
slice 487898/s 72% --
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