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How do I empty out a hash?

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Contributed by vroom on Mar 02, 2000 at 23:36 UTC
Q&A  > hashes

Answer: How do I empty out a hash?
contributed by vroom

You can set it equal to an empty hash or undef it;

%hash=(); undef %hash;
Answer: How do I empty out a hash?
contributed by arno


To delete a key, you don't need to know her value.
Here's my code :

my %hash = ( Carol => 22, Mary => 21, Chris => 30 ); map { delete $hash{$_} } keys %hash;
Update: Of course this makes use of map in void context. Yick. And a couple other suggestions came in by way of followup:

  • delete @hash{(keys %hash)}; # Hash slice
  • %hash = (); # Most efficient method.


Answer: How do I empty out a hash?
contributed by DigitalKitty


You could also iterate over the hash and delete each key/value pair with this:

#!/usr/bin/perl -w use strict; my %hash = ( Carol => 22, Mary => 21, Chris => 30 ); my( $k, $v); while(( $k, $v) = each %hash ) { delete $hash{$k}; }

The previous solutions are more efficient but I thought you might appreciate an alternate method.

Update: Several followups included these suggestions:

  • for (keys %hash) { delete $hash{$_};};
  • delete $hash{$_} for keys %hash;

Both of those methods ignore the values, which are unimportant when deleting hash table entries.

Hope this helps,

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