Specify starting point of foreach enumerator in ruby

Question

I have a rake file that pulls in data from an external CSV file and enumerates through it with:

CSV.foreach(file, :headers => true) do |row|

What is the most effective way (in ruby) to specify the starting point within the spreadsheet?

:headers => true allows me to start importing from the second line, but what if I want to start a line 20?

score 2 · Answer 1 · edited May 26 '14 at 05:01

2

Ruby enumerators include a drop method that will skip over the first n items.

When not passed a block, CSV.foreach returns an enumerator.

You can use

CSV.foreach(file, :headers => true).drop(20).each do |row|

This will skip the first 20 data rows (the header row does NOT count as one of those twenty).

edited May 26 '14 at 05:01

Lucifer

answered Apr 06 '14 at 19:38

akatakritos

1

the only thing is it still load all file in memory. anyway, good solution. – Paritosh Piplewar Apr 06 '14 at 19:55
Yeah just noticed that. Can't think of a good reason it would return an array instead of another enumerator – akatakritos Apr 06 '14 at 19:56
1

See also: http://stackoverflow.com/questions/2200014/ruby-is-there-something-like-enumerabledrop-that-returns-an-enumerator-instead – akatakritos Apr 06 '14 at 20:02
Thanks for the help. I was able to get it to work with CSV.open(file, :headers => true).drop(20).each do |row|. Please edit your answer to show ".open" instead of ".foreach" and I will select it as correct. Thx again. – dmt2989 Apr 06 '14 at 23:59
Oops, I inadvertedly downvoted your answer. Didn't mean to. Can't undo that until you modify the question! I will be watching for it and fix it. – Redoman May 26 '14 at 05:00

score 1 · Accepted Answer · answered Apr 19 '14 at 19:38

1

Use .drop(#rows to ignore):

CSV.open(file, :headers => true).drop(20).each do |row|

answered Apr 19 '14 at 19:38

dmt2989

2 Answers2