What's the best way to make a deep copy of a data structure in Perl?

Anirvan_31100 0
Viewed 13497

Given a data structure (e.g. a hash of hashes), what's the clean/recommended way to make a deep copy for immediate use? Assume reasonable cases, where the data's not particularly large, no complicated cycles exist, and readability/maintainability/etc. are more important than speed at all costs.

I know that I can use Storable, Clone, Clone::More, Clone::Fast, Data::Dumper, etc. What's the current best practice?

clone perl
5 Answers

Clone is much faster than Storable::dclone, but the latter supports more data types.

Clone::Fast and Clone::More are pretty much equivalent if memory serves me right, but less feature complete than even Clone, and Scalar::Util::Clone supports even less but IIRC is the fastest of them all for some structures.

With respect to readability these should all work the same, they are virtually interchangeable.

If you have no specific performance needs I would just use Storable's dclone.

I wouldn't use Data::Dumper for this simply because it's so cumbersome and roundabout. It's probably going to be very slow too.

For what it's worth, if you ever want customizable cloning then Data::Visitor provides hooking capabilities and fairly feature complete deep cloning is the default behavior.

Admin1

My impression is that Storable::dclone() is somewhat canonical.

user_475290

Clone is probably what you want for that. At least, that's what all the code I've seen uses.

Dan_171210

Try to use fclone from Panda::Lib which seems the fastest one (written in XS)

user_26253460

Quick and dirty hack if you're already dealing with JSONs and using the JSON module in your code: convert the structure to a JSON and then convert the JSON back to a structure:

use JSON;

my %hash = (
    obj => {},
    arr => []
);

my $hash_ref_to_hash_copy = from_json(to_json(\%hash));

The only negative possibly being having to deal with a hash reference instead of a pure hash, but still, this has come in handy a few times for me.

user_43161660
Related