Printing keys based on Hash values in Perl

Question

I need to print keys based on vales in hash. Here is the code, I wrote

foreach $value (values %hash)
{
    print "$value\t$hash{$value}\n";
}

Error: I can only print values, but not keys.

Any help will be greatly appreciated.

Thanks

Solution 1

Try with:

for my $key (keys %hash) {
    print "$key\t$hash{$key}\n";
}

Solution 2

Hashes are designed to be accessed by key, not by value. You need to loop over a list of keys, not values.

Then you can use the keys to access the associated values.

foreach my $key (keys %hash) {
    my $value = $hash{$key};
    say "$key = \t$value";
}

Solution 3

print "$_\t$hash{$_}\n" for keys %hash;

Solution 4

One-liner:

map { print "$_\t$hash{$_}\n" } keys %hash;

Solution 5

I would probably use while and each if you want to iterate through keys and values:

while (my ($key, $value) = each %hash) {
    say "$key -> $value";
}

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Comments

[TLP]

You should not use map as a loop statement. Use a for loop instead. E.g. print "$_..." for keys %hash.

[Dave Cross]

It's a simple fix - print map { "$_\t$hash{$_}\n" } keys %hash; :-)

[TLP]

@DaveCross print "$_\t$hash{$_}\n" for keys %hash is even simpler.

[Dave Cross]

Or even say "$_\t$hash{$_}" for keys %hash. But I was talking about the smallest change from what s0me0ne originally had :-)