![]() firstĪs you can see in the above example, both age and birth_date attributes were appropriately formatted. parse (csv, headers : true, converters : ). When parsing CSV you can define which preprocessors you would like to use by passing converters option: csv = "first_name,age,birth_date\nJohn,30," CSV. :date_time - parse values that are dates with the timeĪs I mentioned before, preprocessor is just a simple anonymous function so you can call it directly using the call method: CSV ::Converters.:numeric - parse values that are numbers (integers or floats).:integer - parse values that are integers.A preprocessor is a simple anonymous function that formats the data when parsing a CSV file.īy default, we have the following preprocessors available in the standard library: Solution: to speed up the parsing process, you can use preprocessors. By default, you would receive all values as strings, and you would have to perform additional parsing on your own. Problem: you are parsing a CSV file where some of the values are integers, dates, or formats that require special parsing. With CSV.foreach, you won't load all rows at once and stop processing as soon as you find the row you are looking for. Imagine that you are looking for one row in a file that consists of millions of rows. By iterating the file line by line, you won't use much memory, and you would get access to the rows immediately. The reason is simple: while read and parse methods load the whole file into the memory and then process it, the foreach method process the file line by line without loading all contents at once. Solution: when processing CSV files with Ruby, always use the CSV.foreach method instead of CSV.read or CSV.parse. Problem: you are parsing a large CSV file, and it takes a lot of time to process the whole file, or your server is running out of memory when the process is in the middle. This article is a handy first aid kit when it comes to Ruby and CSV. Although CSV is a straightforward way of formatting the data that later can be used for import/export actions, you may sometimes run into parsing issues. ![]()
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