Ruby convert csv to array of arrays

Question

I'm trying to convert this csv file:

cash,units,boxes,type
12,1,4,"beer"
12,5,4,"wine"
6,3,2,"sugar"
6,5,2,"oats"

to an array of just the rows and not the header. How does one do this?

I have this:

csv = CSV.read(input_path, headers: with_headers)

which gives me a csv object with 5 rows. How do I just convert the content to an array of 4 arrays, where each subarray represents a row?

I believe @steenslag's answer gives the correct result whereas the answer you selected does not (e.g., [12, 1, 4, "beer"], not ["12", "1", "4", "beer"]). No? — Cary Swoveland
– Cary Swoveland, Commented Jun 19, 2018 at 0:12

Bartosz Pietraszko · Accepted Answer · 2018-06-19 09:04:43Z

7

Simply convert the enumerator returned by CSV#each to an array, and shift it to get rid of the headers.

rows = CSV.open(input_path).each.to_a
rows.shift
rows
=> [["12", "1", "4", "beer"], ["12", "5", "4", "wine"], ["6", "3", "2", "sugar"], ["6", "5", "2", "oats"]]

If you prefer a more elegant solution and actually want to treat headers as such:

CSV.open(input_path, headers: true, return_headers: false).map(&:fields)

Please mind that in this case .each would yield CSV::Row objects, not arrays.

edited Jun 19, 2018 at 9:04

answered Jun 18, 2018 at 17:57

Bartosz Pietraszko

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6 Comments

Jwan622 Over a year ago

I don't want the headers though.

Bartosz Pietraszko Over a year ago

Corrected, headers gone.

Cary Swoveland Over a year ago

You need to update your return value as it still shows the headers as the first element of the array that is returned. I suggest drop(1) rather than shift as it avoid the need for the line rows.

Bartosz Pietraszko Over a year ago

@CarySwoveland thanks for pointing out the return value, corrected.

engineersmnky Over a year ago

each.to_a.map is duplicitous where map would be sufficient. Right now it is Enumerator -> Array -> Array but since CSV includes Enumerable just map(&:fields) will return the Array

|

steenslag · Accepted Answer · 2018-06-19 21:29:13Z

6

require "csv"

 p csv = CSV.table("test.csv").drop(1)

Output starts with [[12, 1, 4, "beer"],. that is: numbers where possible, not strings everywhere.

edited Jun 19, 2018 at 21:29

answered Jun 19, 2018 at 0:02

steenslag

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2 Comments

Cary Swoveland Over a year ago

Readers: see the doc for CSV::table It's the same as CSV::new, except (as shown), three of the options keys are assigned default values, one being converters: :numeric, which converts "1" #=> 1, "1.4 #=> 1.4, "cat" => ."cat" and so on. The various options are documented for CSV::new.

engineersmnky Over a year ago

Side note CSV includes Enumerable so CSV.table("test.csv").drop(1) is sufficient over to_a.drop(1) which causes Array -> Array

engineersmnky · Accepted Answer · 2018-06-18 18:54:15Z

-2

I am not sure about this, but I would solve it in this way

CSV.read(path, {:row_sep => :auto, :col_sep => ','}).drop(1)

In your case I believe you have to indicate ',' in the attribute :col_sep

edited Jun 18, 2018 at 18:54

engineersmnky

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answered Jun 18, 2018 at 18:41

Jharol Salvador Rivera

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2 Comments

engineersmnky Over a year ago

:col_sep defaults to "," which makes reasonable sense given "CSV" is traditionally an acronym for "Comma Separated Values"

chevybow Over a year ago

If you're not sure about something its better suited as a comment than an answer.

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