Re^2: Parsing CSV file

Hi Athanasius, The main reason behind my initial posting was that, when I used regular expression to parse the CSV file with one or more lines as shown in the code below, it always worked fine. I couldn't figure out why the print outside the while loop didn't work when using the Text::ParseWords quotewords.

$file = $ARGV[0] or die "Missing CSV file on the command line\n";
open($text, '<:encoding(UTF-8)', $file) or die "Could not open '$file'
+ $!\n";

@fields = ();   # initialize @fields to be empty

while ($line = <$text>)
{
    chomp($line);    # remove the newline at the end of the line
    while ($line =~ m/"([^"\\]*(\\.[^"\\]*)*)",?|([^,]+),?|,/g) {
        push(@fields, defined($1) ? $1 : $3);    # add the matched fie
+ld
    }
    # push(@fields, undef) if $line =~ m/,?/;    # account for an empt
+y last field
}
foreach $field(0..$#fields)
{
    print $field + 1 . " $fields[$field]\n";
}
close $file;
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I am a newcomer to Perl and I am really enjoying it. Thanks for your help.

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Re^3: Parsing CSV file
by Athanasius (Archbishop) on Jul 07, 2016 at 10:35 UTC

Hello Joma,

I’ll make three observations on the regex code shown:

There’s no point in capturing to $2 if that capture is never used. It would be better to use a non-capturing group here:

while ($line =~ m/"([^"\\]*(?:\\.[^"\\]*)*)",?|([^,]+),?|,/g) {
#                          ^^^
    push(@fields, defined($1) ? $1 : $2);
#                                    ^^
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See perlretut#Non-capturing-groupings.

When testing for definedness, Perl’s // (logical defined-or) operator is useful and elegant:
```
    push @fields, $1 // $2;
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```
See perlop#Logical-Defined-Or.
If you had use warnings at the head of your script (and you should!), you would get a Use of uninitialized value warning each time you try to print an array element whose value is undef. You can fix this easily by substituting an empty string:
```
    push @fields, $1 // $2 // '';
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```

Update: ++choroba for pointing out that the Branch Reset pattern (perlre#Extended-Patterns) is a more elegant option here.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^4: Parsing CSV file

by choroba (Cardinal) on Jul 07, 2016 at 12:26 UTC

|

while ($line =~ m/(?|"([^"\\]*(?:\\.[^"\\]*)*)",?|([^,]+),?|,)/g) {
    print $1 // q(), "\n";
}
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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