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Brendan WhitingFront End Web Development Techdegree Graduate 84,696 Points
What's the difference between sys.stdin.read() and input()?
We have both in this video and I'm not sure what the difference is.
Hi Brendan, in this video the "sys.stdin.read()" is described as being able to take a newline and finish your entry with Control+D. input() would finish your entry with the "Enter" key being pressed on your keyboard, so you couldn't include a newline in your data input that way.
That sounds roughly correct, however input() also takes as an argument a string to use as a prompt, while sys.stdin.read() takes the length to read into the user-entered string as an optional argument instead (and provides no prompt - in the video, a print() was provided to serve as a prompt instead). For more information on what these functions are doing though, you can use help(sys.stdin.read) and help(input) while in a Python interpreter, or visit https://docs.python.org/2/library/sys.html for more information about the sys library and its methods, including stdin.
As for your other question, we have to import the sys library because sys.stdin.read() is reflecting a method that exists only in that library. The reason it's so long is that we just imported the library, so we have to reference sys at the beginning of any function from that library, then .stdin() is a function with a .read() method available in it (among others) - so it wouldn't make sense to just say read() without telling Python which read() method you're asking it to use (other functions, including one you write yourself, could include their own read() methods).
If you mean to say why sys is a library instead of being ready for use in Python all the time, that's likely because it would be inefficient for Python to keep libraries loaded if they aren't being used, so the library is kept optional.