Better way of creating an array and pushing values

Question

I'm trying to achieve an array that is a collection of the first element of each row achieved by reading a CSV file.

I have the following:

ids = []
CSV.foreach(filename) do |row|
  ids << row[0]
end
ids

Is there any way to write this in one line? Or neater than that?

What do you expect to be the result of reading without it being an array? Does that make sense? — sawa
– sawa, Commented Sep 14, 2018 at 9:44
If there's a better way to approach it please let me know. My only end aim is to return an array made of the first element of each row of the CSV — Mark
– Mark, Commented Sep 14, 2018 at 9:45

Ben Toogood · Accepted Answer · 2018-09-14 09:41:43Z

2

ids = CSV.read(filename).map(&:first)

answered Sep 14, 2018 at 9:41

Ben Toogood

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4 Comments

Mark Over a year ago

Works perfectly - many thanks will accept when I can (not sure who downvoted you)

sawa Over a year ago

Your edit after my answer made your answer look essentially the same as mine.

Ben Toogood Over a year ago

@sawa using read over foreach was an improvement but it didn't answer the full question of getting the first element and assigning the value to ids.

Stefan Over a year ago

"using read over foreach was an improvement" – read parses the entire file into an array, whereas foreach reads it row by row. The latter is probably more memory efficient, especially for huge CSV files.

sawa · Accepted Answer · 2018-09-14 09:42:20Z

0

Simply do:

CSV.read(filename)

If you wanted to collect only the first column, then:

CSV.read(filename).map{|row| row[0]}

answered Sep 14, 2018 at 9:42

sawa

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