如何在Perl中找到哈希中的键数？

Question

如何在散列中找到键的数量，比如使用$#作为数组？

Answer 1

scalar keys %hash

or just

keys %hash

if you're already in a scalar context, eg my $hash_count = keys %hash or print 'bighash' if keys %hash > 1000 .

Incidentally, $#array doesn't find the number of elements, it finds the last index. scalar @array finds the number of elements.

Answer 2

we can use like this too

my $keys = keys(%r) ;
print "keys = $keys" ;

 0+(keys %r) 

Answer 3

But not after Perl 5.10:

use feature ":5.10";
my %p = ();
say $#%p;

# $# is no longer supported

and worse:

use feature ":5.10";
my %p = (a=>1, b=>2, c=>3);
say $#{%p};

# -1

Answer 4

print scalar keys %hash;

or

$X = keys %hash;
print $X;

keys %hash returns the value of keys in the list context that further changes into the scalar context (when assigning to scalar variable).

Answer 5

This will work in easy way and for any size of a hash.

print scalar keys %hash;