Data::Printer - colored pretty-print of Perl data structures and objects
use Data::Printer; my @array = qw(a b); $array[3] = 'c'; p @array; # no need to pass references!
Code above will show this (with colored output):
[ [0] "a", [1] "b", [2] undef, [3] "c", ]
You can also inspect Objects:
my $obj = SomeClass->new; p($obj);
Which might give you something like:
\ SomeClass { Parents Moose::Object Linear @ISA SomeClass, Moose::Object public methods (3) : bar, foo, meta private methods (0) internals: { _something => 42, } }
If for some reason you want to mangle with the output string instead of printing it to STDERR, you can simply ask for a return value:
# move to a string my $string = p(@some_array); # output to STDOUT instead of STDERR print p(%some_hash); # or even render as HTML use HTML::FromANSI; ansi2html( p($object) );
Finally, you can set all options during initialization, including coloring, identation and filters!
use Data::Printer { color => { 'regex' => 'blue', 'hash' => 'yellow', }, filters => { 'DateTime' => sub { $_[0]->ymd }, 'SCALAR' => sub { "oh noes, I found a scalar! $_[0]" }, }, };
You can ommit the first {} block and just initialize it with a regular hash:
use Data::Printer deparse => 1, sort_keys => 0;
And if you like your setup better than the defaults, just put them in a '.dataprinter' file in your home dir and don't repeat yourself ever again :)
Data::Dumper is a fantastic tool, meant to stringify data structures in a way they are suitable for being eval'ed back in.
eval
The thing is, a lot of people keep using it (and similar ones, like Data::Dump) to print data structures and objects on screen for inspection and debugging, and while you can use those modules for that, it doesn't mean mean you should.
This is where Data::Printer comes in. It is meant to do one thing and one thing only:
display Perl variables and objects on screen, properly formatted (to be inspected by a human)
If you want to serialize/store/restore Perl data structures, this module will NOT help you. Try Storable, Data::Dumper, JSON, or whatever. CPAN is full of such solutions!
Below are all the available colorizations and their default values. Note that both spellings ('color' and 'colour') will work.
use Data::Printer { color => { array => 'bright_white', # array index numbers number => 'bright_blue', # numbers string => 'bright_yellow', # strings class => 'bright_green', # class names undef => 'bright_red', # the 'undef' value hash => 'magenta', # hash keys regex => 'yellow', # regular expressions code => 'green', # code references glob => 'bright_cyan', # globs (usually file handles) repeated => 'white on_red', # references to seen values }, };
Data::Printer offers you the ability to use filters to override any kind of data display. The filters are placed on a hash, where keys are the types - or class names - and values are anonymous subs that receive two arguments: the item itself as first parameter, and the properties hashref (in case your filter wants to read from it). This lets you quickly override the way Data::Printer handles and displays data types and, in particular, objects.
use Data::Printer { filters => { 'DateTime' => sub { $_[0]->ymd }, 'HTTP::Request' => sub { $_[0]->uri }, }, };
Perl types are named as ref calls them: SCALAR, ARRAY, HASH, REF, CODE, Regexp and GLOB. As for objects, just use the class' name, as shown above.
ref
Note: If you plan on calling p() from within an inline filter, please make sure you are passing only REFERENCES as arguments. See "CAVEATS" below.
p()
You may also like to specify standalone filter modules. Please see Data::Printer::Filter for further information on this, including useful filters that are shipped as part of this distribution.
Data::Printer provides the nice, short, p() function to dump your data structures and objects. In case you rather use a more explicit name, already have a p() function (why?) in your code and want to avoid clashing, or are just used to other function names for that purpose, you can easily rename it:
use Data::Printer { alias => 'Dumper' }; Dumper( %foo );
I tried to provide sane defaults for Data::Printer, so you'll never have to worry about anything other than typing "p( $var )" in your code. That said, and besides coloring and filtering, there are several other customization options available, as shown below (with default values):
"p( $var )"
use Data::Printer { name => 'var', # name to display on cyclic references indent => 4, # how many spaces in each indent hash_separator => ' ', # what separates keys from values index => 1, # display array indices multiline => 1, # display in multiple lines (see note below) max_depth => 0, # how deep to traverse the data (0 for all) sort_keys => 1, # sort hash keys deparse => 0, # use B::Deparse to expand subrefs class => { internals => 1, # show internal data structures of classes inherited => 'none', # show inherited methods, # can also be 'all', 'private', or 'public'. expand => 1, # how deep to traverse the object (in case # it contains other objects). Defaults to # 1, meaning expand only itself. Can be any # number, 0 for no class expansion, and 'all' # to expand everything. sort_methods => 1 # sort public and private methods }, };
Note: setting multiline to 0 will also set index and indent to 0.
multiline
0
index
indent
Data::Printer tries to let you easily customize as much as possible regarding the visualization of your data structures and objects. But we don't want you to keep repeating yourself every time you want to use it!
To avoid this, you can simply create a file called .dataprinter in your home directory (usually /home/username in Linux), and put your configuration hash reference in there.
.dataprinter
/home/username
This way, instead of doing something like:
use Data::Printer { colour => { array => 'bright_blue', }, filters => { 'Catalyst::Request' => sub { my $req = shift; return "Cookies: " . p($req->cookies) }, }, };
You can create a .dataprinter file like this:
{ colour => { array => 'bright_blue', }, filters => { 'Catalyst::Request' => sub { my $req = shift; return "Cookies: " . p($req->cookies) }, }, };
and from then on all you have to do while debugging scripts is:
use Data::Printer;
and it will load your custom settings every time :)
The following are volatile parts of the API which are subject to change at any given version. Use them at your own risk.
You can override global configurations by writing them as the second parameter for p(). For example:
p( %var, color => { hash => 'green' } );
As of Data::Printer 0.11, you can create complex filters as a separate module. Those can even be uploaded to CPAN and used by other people! See Data::Printer::Filter for further information.
You can't pass more than one variable at a time.
p($foo, $bar); # wrong p($foo); # right p($bar); # right
You are supposed to pass variables, not anonymous structures:
p( { foo => 'bar' } ); # wrong p %somehash; # right p $hash_ref; # also right
If you are using inline filters, and calling p() (or whatever name you aliased it to) from inside those filters, you must pass the arguments to p() as a reference:
use Data::Printer { filters => { ARRAY => sub { my $listref = shift; my $string = ''; foreach my $item (@$listref) { $string .= p( \$item ); # p( $item ) will not work! } return $string; }, }, };
This happens because your filter function is compiled before Data::Printer itself loads, so the filter does not see the function prototype. As a way to avoid unpleasant surprises, if you forget to pass a reference, Data::Printer will generate an exception for you with the following message:
'If you call p() inside a filter, please pass arguments as references'
Another way to avoid this is to use the much more complete Data::Printer::Filter interface for standalone filters.
If you find any, please file a bug report.
Data::Dumper
Data::Dump
Data::Dumper::Concise
Data::Dump::Streamer
Data::TreeDumper
Copyright 2011 Breno G. de Oliveira <garu at cpan.org>. All rights reserved.
<garu at cpan.org>
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.
BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
To install Data::Printer, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Data::Printer
CPAN shell
perl -MCPAN -e shell install Data::Printer
For more information on module installation, please visit the detailed CPAN module installation guide.