How can I modify an existing Excel workbook with Perl? - perl

Question

With Spreadsheet::WriteExcel, I can create a new workbook, but what if I want to open an existing book and modify certain columns? How would I accomplish that?
I could parse all of the data out of the sheet using Spreadsheet::ParseExcel then write it back with new values in certain rows/columns using Spreadsheet::WriteExcel, however. Is there a module that already combines the two?
Mainly I just want to open a .xls, overwrite certain rows/columns, and save it.

Answer 1

Spreadsheet::ParseExcel will read in existing excel files:
my $parser = Spreadsheet::ParseExcel->new();
# $workbook is a Spreadsheet::ParseExcel::Workbook object
my $workbook = $parser->Parse('Book1.xls');
But what you really want is Spreadsheet::ParseExcel::SaveParser, which is a combination of Spreadsheet::ParseExcel and Spreadsheet::WriteExcel. There is an example near the bottom of the documentation.

Answer 2

If you have Excel installed, then it's almost trivial to do this with Win32::OLE. Here is the example from Win32::OLE's own documentation:
use Win32::OLE;
# use existing instance if Excel is already running
eval {$ex = Win32::OLE->GetActiveObject('Excel.Application')};
die "Excel not installed" if $#;
unless (defined $ex) {
$ex = Win32::OLE->new('Excel.Application', sub {$_[0]->Quit;})
or die "Oops, cannot start Excel";
}
# get a new workbook
$book = $ex->Workbooks->Add;
# write to a particular cell
$sheet = $book->Worksheets(1);
$sheet->Cells(1,1)->{Value} = "foo";
# write a 2 rows by 3 columns range
$sheet->Range("A8:C9")->{Value} = [[ undef, 'Xyzzy', 'Plugh' ],
[ 42, 'Perl', 3.1415 ]];
# print "XyzzyPerl"
$array = $sheet->Range("A8:C9")->{Value};
for (#$array) {
for (#$_) {
print defined($_) ? "$_|" : "<undef>|";
}
print "\n";
}
# save and exit
$book->SaveAs( 'test.xls' );
undef $book;
undef $ex;
Basically, Win32::OLE gives you everything that is available to a VBA or Visual Basic application, which includes a huge variety of things -- everything from Excel and Word automation to enumerating and mounting network drives via Windows Script Host. It has come standard with the last few editions of ActivePerl.

Answer 3

There's a section of the Spreadsheet::WriteExcel docs that covers Modifying and Rewriting Spreadsheets.
An Excel file is a binary file within a binary file. It contains several interlinked checksums and changing even one byte can cause it to become corrupted.
As such you cannot simply append or update an Excel file. The only way to achieve this is to read the entire file into memory, make the required changes or additions and then write the file out again.
You can read and rewrite an Excel file using the Spreadsheet::ParseExcel::SaveParser module which is a wrapper around Spreadsheet::ParseExcel and Spreadsheet::WriteExcel. It is part of the Spreadsheet::ParseExcel package.
There's an example as well.

Answer 4

The Spreadsheet::ParseExcel::SaveParser module is a wrapper around Spreadsheet::ParseExcel and Spreadsheet::WriteExcel.
I recently updated the documentation with, what I hope, is a clearer example of how to do this.