Perl CSV to Hash of Arrays natively - csv

Question

I'm trying to build an associative array from a csv file that stores only unique keys. All without using extra features like Text::CSV
An example text file:
emp1,dept1,1090
emp2,dept2,8920
emp3,dept1,3213
emp3,dept2,3234
I would like the data to be organized by dept to look like
$hash = {
dept=>[dept1, dept2, dept3]
}
and within each dept to have its respective emp and ids
So far, I have tried
my %hash;
while (<$fh>){
my #data = split(/,/, $fh);
push #{$hash{$_}}, shift #data
for qw(emp dept id);
}
However, this does not seem to fill the arrays properly and instead just initializes the arrays with no data in them. I've looked all over for examples of how to do this but my searches always contain people mentioning Text::CSV

Answer 1

Your first problem is the with this line
my #data = split(/,/, $fh);
You are splitting of the filehandle, not the data returned from the while statement. That is stored in $_
Below is you code changes to fix the split line. I'm also using the inline DATA filehandle to make it easier on myself. Finally, I've added a call to Data::Dumper to see what is getting stored into the hash.
use Data::Dumper ;
my %hash;
while (<DATA>){
my #data = split(/,/, $_);
push #{$hash{$_}}, shift #data
for qw(emp dept id);
}
print "Hash is " . Dumper(\%hash);
__DATA__
emp1,dept1,1090
emp2,dept2,8920
emp3,dept1,3213
emp3,dept2,3234
Running that gives this, which shows the second issue -- you are including a newline in the id column
Hash is $VAR1 = {
'dept' => [
'dept1',
'dept2',
'dept1',
'dept2'
],
'emp' => [
'emp1',
'emp2',
'emp3',
'emp3'
],
'id' => [
'1090
',
'8920
',
'3213
',
'3234
'
]
};
Fix that with a call to chomp before the split line
use Data::Dumper ;
my %hash;
while (<DATA>){
chomp;
my #data = split(/,/, $_);
push #{$hash{$_}}, shift #data
for qw(emp dept id);
}
print "Hash is " . Dumper(\%hash);
__DATA__
emp1,dept1,1090
emp2,dept2,8920
emp3,dept1,3213
emp3,dept2,3234
output is now
Hash is $VAR1 = {
'id' => [
'1090',
'8920',
'3213',
'3234'
],
'emp' => [
'emp1',
'emp2',
'emp3',
'emp3'
],
'dept' => [
'dept1',
'dept2',
'dept1',
'dept2'
]
};
That looks better, but you have duplicates in the hash. To deal with that, I'm going to store the data read from the CSV as a hash-of-hashes. That will get rid of the duplicates
my %hash;
my #cols = qw( emp dept id);
while (<DATA>)
{
chomp $_;
my #data = split /,/, $_ ;
for my $i (0 .. #cols-1)
{
# Store as a hash of hashes
$hash{ $cols[$i] }{ $data[$i] } ++;
}
}
print "Hash is " . Dumper(\%hash);
That looks better - the duplicates are removed
Hash is $VAR1 = {
'dept' => {
'dept2' => 2,
'dept1' => 2
},
'emp' => {
'emp3' => 2,
'emp2' => 1,
'emp1' => 1
},
'id' => {
'3213' => 1,
'8920' => 1,
'1090' => 1,
'3234' => 1
}
};
Your requirement was to has a hash of arrays, so add a final step to dump the hash-of-hashes into the format you require
my %result;
for my $col (keys %hash)
{
push #{ $result{$col} }, sort keys %{ $hash{$col} } ;
}
print "Hash is " . Dumper(\%result);
That outputs this
Hash is $VAR1 = {
'dept' => [
'dept1',
'dept2'
],
'emp' => [
'emp1',
'emp2',
'emp3'
],
'id' => [
'1090',
'3213',
'3234',
'8920'
]
};