You will work with one or two partners assigned to you for this assignment. Do the individual work on your own computers, but share a single git repository for your project. Put both/all of your names in the comments at the top of each source file.
To learn about:
Here's the quick summary of your tasks. Much more detailed instructions are in the numbered sections below.
The rest of this document contains lots and lots of details. Go slowly, write down your questions as you go, and pay attention to error messages and other information that appears on your screens. Also, talk to your partner about each step: Did you get what happened there? Should we try something different? Should we reread the instructions? What does that sentence mean? Maybe we should bug Jeff or post on Slack about this one...
If you get stuck or just want a little elaboration on a concept, don't hesitate to ask for help, in your discussion group, in office hours, or on Slack.
For the rest of this document, and sometimes in other exercises, I will refer to the partner whose repo you're using for this project as Alice, and each other partner as Bob. This makes writing instructions a lot easier than referring to "the partner whose repo you're using for this project" and "the partner whose repo you're not using for this project". Alice and Bob have been used in computer-related exposition for a long time because they love communicating collaboratively and they're handy to have around.
Have fun!
After you have filled out the tell-me-your-GitHub-name survey, wait a bit until I can add you to the GitHub Classroom list, and then follow these instructions on how to obtain your GitHub repository for CS257.
This process will give you access to a git repository. A repository is essentially a folder in which you can store whatever files and subfolders you want. What makes a repository more than a folder, however, is that the version control system (git, in this case) keeps track of all the changes that get made to the files in the repository. This saving of history makes it possible for you to retrieve old work, track down the time when a bug was introduced (and who introduced it), collaborate on a project with a team of programmers, easily back up your work, etc. Version control systems are a bit of a hassle to learn for the first time, but they're indispensable programming tools and unquestionably worth the effort.
That link you got on the "You are ready to go!" page in Step 1 above? You need it now. Right now, your repository is stored only on the GitHub server. To add files to it, you'll need to clone a copy of the repository onto your working computer. You will then add files to your local copy of the repository and eventually, you'll manually push your changes back up to GitHub.
You'll do your cloning via the following operation (or its GUI equivalent):
where the "..." is the remainder of the link you got from the "You are ready to go!" page. You should now have a folder called "assignments-yourgithubname", which contains only a subfolder called ".git". You can move this folder wherever it's convenient for you. (Curious about the contents of the .git folder? Go ahead and poke around to see what's there. It gets more interesting, of course, after you add some files.)
IMPORTANT FOR WINDOWS USERS: When you do this, you will need to be careful about where you put your files. If you put your repository inside the Linux file tree (by, say, doing "cd" at the terminal prompt to get to your Linux home directory and then doing "git clone ..." to put your git repository there), you'll run into file permissions trouble if you try to access your files using a Graphical User Interface (GUI) tool like Atom or Notepad. There's a simple solution. You can use your terminal to access files in the normal Windows file system (say, on your C drive) by doing this:
(By the way, this sad complexity of using Linux files in Windows may soon come to an end.)
I'll assign you your partner for this assignment. Get in touch promptly. Personal-message me on Slack if your partner is unresponsive after a half-day or so.
Once you're talking, set up a time to do this exercise together. I recommend setting up a Zoom call and planning to make use of screen sharing—I think this will be easier than distanced and masked in the same room. If Alice is doing something, then Alice shares her screen with Bob, and Alice does the typing while Bob watches. Reverse that when it's Bob's turn to do something.
I also recommend planning for a two-hour time slot at first. It might take you more or less time than that, but it's important during this exercise to go slowly and think through every step and the lessons to be learned from every step.
It doesn't matter which partner's repository is the one you use for this assignment, but you need to pick one. Then, the owner of the chosen repository (Alice, that is) will need to add Bob(s) as collaborator(s) on Alice's repository. Try to figure out how to do this on github.com. Ask questions if you run into problems.
Once all partners are collaborators on the chosen repo, everyone should "git clone" it to their working machines.
Note that those three "git status" invocations are there because I want you to see the status messages before and after the "git add". This sort of exploration is part of coming to understand how git works, but it's also something I often do myself to make sure I don't make big changes too fast. Going a little bit slowly like this saves me a lot of hassle in the long run.
(Alice? Hands off the keyboard. Bob is sharing his screen now. Fair is fair.)
Bob, at your terminal on your computer, cd to your clone of Alice's repository, and do
Does the hello.py file appear in your copy of the repo? It should. If it doesn't, try to figure out what went wrong, then ask for help if you're stuck.
Bob: Change something in hello.py (add a comment, add a print statement, whatever). Then do the git status/add/status/commit/push sequence from section 5 above to get your changes included in the master copy on github.com.
Alice: do a "git pull" and see if you ended up with Bob's version of the code.
While we work on a project, it's common for the project directory to accumulate files that aren't really part of the project. For example, if you write program.py and module.py and program.py includes an "import module" statement, you may discover a module.pyc in your working directory. This isn't source code, and it doesn't matter if you delete it—it'll just get recreated next time you "import module". So you don't want that litter included in your repository.
There are lots of other examples of files that shouldn't be saved in a repo. Like the .DS_Store files the macOS Finder generates whenever you look at a folder in a window or the .class files you get when you compile a .java file. Accidentally adding these files to your repository is all too easy. And since these files typically change every time you run the Python program or recompile the Java program or look at the folder in a window, all those changes get added to the repository every time you commit, which makes every clone of your repo take up a lot of unnecessary disk space. It's a mess, and we hate messes.
To prevent you from accidentally adding these extraneous files to your repository, you can tell git to ignore them completely via a .gitignore file. Like so:
IMPORTANT ODDITY: by default, macOS, Windows, and Unix command shells don't display files whose names start with a period. So if you open your repo's top-level folder in a macOS Finder window, you probably won't see your .gitignore file. Similarly, a simple:
command at a Unix command line won't show you .gitignore. But this command does:
(the "-a" stands for "all").
All done.