40 — CSV: several fields on one line

Guide 38 put one thing on each line. To put two or more on a line — a name and a count, say — separate them with a comma. A file made that way is called a CSV.

A program that uses files does not run on the site.

#Steps

1. Split one line by comma:

   set text to apples,3
   set fields to text split by comma
   show the first of fields
   show the last of fields
   

   copyrun it →

   apples and 3 come out separately.

2. Several lines go in a list. A comma separates items when a list is written out, so a line that itself contains a comma is kept in a name first and appended:

   set first to apples,3
   set second to grapes,5
   set rows to an empty list
   append first to rows
   append second to rows
   

   copyrun it →

3. Save it and read it back, joined by newline and split by line:

   set rows to list of a, b
   set text to rows joined by newline
   write text to "stock.csv"
   read "stock.csv" into memo
   set lines to memo split by line
   

   copyrun it →

4. Split each line by comma and you have the fields:

   set lines to list of apples,3
   for each row in lines
       set fields to row split by comma
       show the first of fields
       show the last of fields
   end
   

   copyrun it →

5. All of it:

   set first to apples,3
   set second to grapes,5
   set rows to an empty list
   append first to rows
   append second to rows
   set text to rows joined by newline
   write text to "stock.csv"
   read "stock.csv" into memo
   set lines to memo split by line
   for each row in lines
       set fields to row split by comma
       show the first of fields
       show the last of fields
   end
   

   copyrun it →

   The comma you split on and the comma you join with are different. Splitting cuts on a bare comma; joining puts a comma and a space (, ) between. Text a person reads wants the space; a file being cut apart does not have one.

#Try it yourself

Add a third field — apples,3,red — and take the middle one with item 2 of fields.

#What you learned

• <text> split by comma turns one line into a list of fields.
• A comma separates items when a list is written out, so a line containing one goes into a name first.
• Join by newline to save, split by line to read, split by comma for the fields.
• Splitting uses ,; joining uses , .