Testing if a HoH key exists

Jeri has asked for the wisdom of the Perl Monks concerning the following question:

Hi! I'm trying to see if a nested Hash key exists. If it does, I want to delete it. Here's what I've written.

if (exists %{$rHoH_ProteinFamilies->{$proteinfamily}->{$PROTEIN}})
{
delete $rHoH_ProteinFamilies->{$proteinfamily}->{$PROTEIN};
}
[download]

Here's the error.

exists argument is not a HASH or ARRAY element or a subroutine at HoH.pl line 123.

Thanks in advance!

Comment on Testing if a HoH key exists Select or Download Code

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Re: Testing if a HoH key exists by johnny_carlos (Scribe) on Nov 11, 2011 at 16:56 UTC
I think it's because you are dereferencing your hash, so it is no longer a key, but a value. Try just: exists $rHoH_ProteinFamilies->{$proteinfamily}->{$PROTEIN}	[reply]
Re^2: Testing if a HoH key exists by Jeri (Scribe) on Nov 11, 2011 at 17:09 UTC
That worked! Thanks. Before I was iterating through the hash using a for loop and forgot that I was still using an entire hash and not a element.	[reply]
Re: Testing if a HoH key exists by chilledham (Friar) on Nov 11, 2011 at 16:56 UTC
`exists` works on single elements of a hash (or array), not an entire hash (or array). (Monks, is is appropriate to say `exists` works in scalar context?) If you remove the % sigil and first set of curlies (leaving `if (exists $rHoH_ProteinFamilies->{$proteinfamily}->{$PROTEIN}`) Your error should go away. See `perldoc -f exists`	[reply] [d/l] [select]
Re: Testing if a HoH key exists by hbm (Hermit) on Nov 11, 2011 at 17:19 UTC
You can just delete the key without testing, unless you plan to do something else in that 'if' block.	[reply]
Re^2: Testing if a HoH key exists by Jeri (Scribe) on Nov 11, 2011 at 17:20 UTC
What if the key doesn't exist? Will it throw an error? (I would test it but my data is convoluted)	[reply]
Re^3: Testing if a HoH key exists by hbm (Hermit) on Nov 11, 2011 at 17:29 UTC
It will not throw an error. Try simply, `perl -e 'use strict; use warnings; my %H; delete $H{jeri}'` [download]	[reply] [d/l]
Re^4: Testing if a HoH key exists by Jeri (Scribe) on Nov 11, 2011 at 17:54 UTC
Re^5: Testing if a HoH key exists by hbm (Hermit) on Nov 11, 2011 at 18:16 UTC