Editing DS4UX (Spring 2016)/Reading and writing files (section)

== Important syntax concepts ==

#using <code>with open(FILENAME, "r") as VARIABLE</code> will almost always be the best way to open a file (for reading or writing). This saves you some steps, and makes sure that the file is properly closed (removed from working memory) once you're done with it. There are other patterns for opening files, but I suggest you get used to this pattern before you explore any others.
#when you specify <code>"r"</code> after the filename in <code>open()</code> you're saying whether you want to open the file to READ it; when you specify <code>"w"</code>, you are saying you want to open the file (or create it, if it doesn't exist) so that you can write to it—add data into the file to save. There are some other options for reading and writing, such as <code>"rb"</code> and <code>"wb"</code>, which are used in different circumstances and for different types of data. We'll cover these in less detail next week. 
#<code>.readlines()</code> vs <code>csv.reader</code>: both of these are functions that make it easy to read through a file object line-by-line once you have opened the file. <code>csv.reader</code> provides you with additional ''parameters'' that allow you to control how the data from the file is interpreted, which often comes in handy when dealing with messy data, but to use it you have to <code>import csv</code> first. The same goes for <code>write</code>, used to write the .tsv file in the first script, and <code>csv.writer</code>, used to write the .csv file in the second script.

[[Category:DS4UX (Spring 2016)]]