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phigginsphiggins
Oct 4, 2016
71311b5 · Oct 4, 2016

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README.md

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Your task is to write a CSV (Comma Separated Values) parser.

CSV is a plain text data format for storing tabular data. The files usually end with the .csv extension, and a typical CSV file might look like this:

name,breed,weight
Francis,Samoyed,32
Kieran,Lab,90
Renata,Coonhound,29
Ving,Boxer,51
Brian,Lab,51

For more information about the CSV format:

Steps:

  1. Write some code that can parse the sample CSV file above. Test file: dogs.csv

One way this could work would be to write a method that does the following:

>> csv_data = File.read("dogs.csv") ; csv_data.length
=> 97
>> csv_parser(csv_data)
=> [["name", "breed", "weight"], ["Francis", "Samoyed", "32"], ["Kieran", "Lab", "90"], ["Renata", "Coonhound", "29"], ["Ving", "Boxer", "51"], ["Brian", "Lab", "51"]]

  1. While the C in CSV stands for comma, not all CSV files use , as the delimiter between values in a row. Some common alternatives are tabs (\t) or spaces ( ). Modify your parser so that the caller of your code can specify an alternative delimiter. Test file: dinosaurs.csv

  2. When a value in a CSV file contains the delimiter, the entire value needs to be quoted. The double quote character (") is typically used for this. Update your parser to handle quoted values. Test file: cat_breeds.csv

  3. The vast majority of CSV files will use double quotes (") as their quote character, but this is not necessarily the case. Modify your parser so that the caller of your code can specify an alternate quote character. Test file: contacts.csv

  4. If a quoted value contains the quote character, the quote appearing in the value needs to be escaped by doubling the quote character. Update your CSV parser to handle this. Test file: routes.csv

  5. Most CSV files have one record per line, but some will have multi-line values, that is values that contain a newline character. Modify your parser to support this. Test file: cars.csv

Taking it further:

  • Add an interface to your parser that returns a hash with headers as keys. Using dinosaurs.csv, the first element of the output should look like:
{
  "Name" => "Acrocanthosaurus (top-spined lizard)",
  "Height" => "19 ft. 5.8 m",
  "Length" => "40 ft. 12.2 m",
  "Weight" => "6,000lbs 2,722kg",
}
  • Add an interface to your parser that takes a block and yields destructured arrays. Using dinosaurs.csv, the interface might look something like:
my_parsing_method do |name, height, length, weight|
  # the first result would have name == "Acrocanthosaurus (top-spined lizard)", etc.
end

  • Add an interface to your parser that returns a collection of row objects (what cool stuff could you do with this?)

  • Modify your CSV parser to detect if an alternate delimiter or quote character is present in a CSV file instead of making the user specify it.

  • Write a utility that normalizes CSV files to a standard format.

  • Rewrite your parser with ruby's StringScanner, or a fully featured parsing library like https://github.com/evanphx/kpeg or https://github.com/tenderlove/racc