Setting up the programming environment on Windows

Transcription

1 Setting up the programming environment on Windows Author: Michael Uhl ( contact: uhlm[at]informatik.uni freiburg.de ) Date: The easiest way to set up the programming environment on Windows is to use our Linux virtual machine (VM) (supplied as VirtualBox image) which allows you to immediately start programming in Python 3. This includes checking the style of your code with flake8 and unit testing, as well as subversion (SVN) for version control in combination with Daphne. The VirtualBox image we want to use (Lubuntu Linux 16.04) will be supplied in the first week. First you need to download VirtualBox (it's for free + open source) in order to run the image: Select the latest Windows version. The installation routine is straight-forward, you don't need to change anything here. Once the installation is completed, extract the downloaded image file and double-click on it in order to import it into VirtualBox. The import settings should be fine, just make sure you have enough disc space available, since the image will take up around ~ 6 GB on your hard drive. The image by default also consumes 1,5 GB RAM, If you feel like this is too much for your system, you can lower the amount of RAM the image consumes (inside VirtualBox click on System to change). It is advised that you keep at least 1 GB RAM (1028 MB) which should still be okay for the programming tasks in the course. If you still have problems please contact us. Once imported, the Linux image is available inside VirtualBox. Run the image. Inside the Linux virtual machine NOTE the Linux image account ID ( student ) and the corresponding password student. Once Linux has booted up, you basically have a full Linux operating system inside Windows waiting at your disposal. Log in with the student account and the given password. The virtual machine should be able to access the Internet automatically (problems can occur with firewalls, in this case check whether your firewall blocks VirtualBox). You can use the file manager to navigate the file system, or open up a terminal window (LXTerminal) to use the command line. Note the bottom blue button where you can access software and settings. There you can also change the system language (Preferences Language Support, drag e.g. Deutsch to the top, click Apply system-wide + confirm with your password and restart). The button for shutting down / restarting Linux is on the bottom right. To change the keyboard layout (e.g. German / English keyboard), there is a switch on the bottom right (click DE, US or right-click + Keyboard Layout Settings to add more layouts).

2 Getting started with the VM To get started with the programming, create a course directory somewhere (e.g. inside home/student/documents/ and name it AlgoDat ). To do this in the terminal (LXTerminal), open a terminal by double-clicking on its desktop icon. Then in the terminal, type in the following commands to go to the Documents folder, create the directory using the mkdir command and enter the directory: cd /home/student/dokumente/ mkdir AlgoDat cd AlgoDat Now it's time to check out your (yet empty) SVN repository on Daphne for the first time. Make sure that you already logged in on Daphne before that (since this will trigger Daphne to automatically create a repository for you). Daphne login link for ESE students: Back in the terminal, type in the following command to checkout your repository: svn checkout freiburg.de/ws1718/algodatese/svn/<your user name> Use your own user name for the checkout. It should be your university account name (usually first letters of first and last name followed by a number). If you do svn checkout for the first time, you also need to enter the password for your Linux system ( student ) once at the beginning and at the end (Passwort für GNOME-Schlüsselring login). In between, enter your university user account name and the corresponding password. Once checked out, a local copy of your repository is available in your folder (with directory name = your user name). Enter the directory: cd <your user name> Now you can download the Python template from our course website. It contains an implementation of the MinSort algorithm and a Makefile which easily lets you execute the unit tests and style checking by flake8. You can do this directly inside your svn directory using the terminal with: wget freiburg.de/lehre/courses/2017_ws/v_aud/template_python.zip Unpack the template file and enter the containing folder uebungsblatt_00 : unzip template_python.zip cd uebungsblatt_00 Understanding the Makefile Inside uebungsblatt_00 there are two files, Makefile and minsort.py. Under Linux a Makefile is often used to give instructions on what to do for the different defined cases (also called recipes) defined in the Makefile. In our case these are the recipes all, test, checkstyle and clean. Any of these just executes the commands attached to it on the command line (note the tabulator before the commands which is essential). For example, make test would run the test command, which

3 essentially calls each.py file (Python source code files) with python3 -m doctest to execute the doctests inside the code files (if there are any). For convenience, we used a variable TEST_CMD to store the Python command line call in. Likewise, make test would run the checkstyle program flake8 to check your Python code for stylistic errors. Typing in just make will execute the first command, which is make all in our case, corresponding to calling make test and make checkstyle right after each other. To clean up temporary files created by the Python interpreter, you should run make clean such that you do not add these temporary files to your SVN repository by accident. This can happen if e.g. you add a whole folder by typing in svn add uebungsblatt_00. Exercise sheet naming convention The template was just an example, but it showed you the naming convention that you need to follow such that Jenkins can successfully check your code (after you committed your code to Daphne). For the first exercise you will thus create a directory called uebungsblatt_01, for the second uebungsblatt_02, and so on. Python unit testing and checkstyle Now have a look at the Python source code file minsort.py in the template. You will see that there is a part starting with if name == main : which gets executed if you run the source code file the usual way on the command line (python3 minsort.py). Note the use of indentations in the code, which is an essential feature of Python. These are used in Python instead of using brackets, like in Java or C++, to define code blocks. In this case, the minsort function gets executed which expects a list (the standard Python data type corresponding to an array). The function then sorts the list using the MinSort algorithm implemented inside and returns the sorted list. Note that in Python you can easily write unit tests by putting them in the comment section below the function header. These comment sections are also called docstrings and the unit tests are called doctests. You can find three tests here (starting with >>> function_call on the first line, and the expected output on the second line). The first two should be of interest for you, since they cover the usual use case plus a special case where an empty list [] is given to the function. If you execute make or make test, Python will look for these unit tests inside the docstrings and execute them. If the expected output is returned, nothing gets reported on the command line (meaning that no error occurred). You can provoke an error e.g. by typing in a wrong expected output (e.g. a wrongly sorted list) to check if it works. As for the checkstyle, flake8 follows the PEP8 style guide, which can be quite picky regarding your style, but will ultimately help you and others to better + faster comprehend your code (especially after returning to it after some while). Installing code editors / additional software You can use whatever code editor / integrated development environment (IDE) you like for writing your code. The basic editor provided in the image (gedit) will do fine for that, but of course you can also use more sophisticated editors (check the internet for recommended Python editors and experiment). To install new software / editors on the Linux machine, you can use the apt-get install command, e.g. for installing the generic Geany IDE:

4 sudo apt get install geany Every time you install new software, you have to enter your account password. NOTE that in this case you do not so see any asteriks shown for your typed-in password. This is normal: just enter your password and hit return. Using SVN Subversion (SVN) allows us to keep track of code changes and code storage on a remote repository. In our case, each student has his or her own SVN repository located on Daphne. You can add your working directory and commit it to Daphne (make sure to first remove any temporary files with make clean ): svn add uebungsblatt_01 This will add the whole folder content / mark it for committing to the repository. The commit should be done with an informative message (-m parameter), shortly summarizing what you are about to commit: svn commit m "this is my initial revision" The same way you can also add and commit more files later or commit changes to your files. In general it is advisable to first write some unit tests and then implement the functionality until all the tests succeed (test-driven development). You should also include the Makefile in every uebungsblatt_xx folder you are creating. To get the most recent copy from your remote repository on Daphne, use svn update : svn update This will be the case e.g. after your tutor has added a file feedback-tutor.txt to inform you about the corrections of the last exercise sheet. More useful SVN commands: Show all files and their status: svn status Show changed files: svn diff Delete files from the repository: svn delete... Rename or move files: svn mv... Remember that you always have to commit the changes that you do locally on your machine (e.g. with delete, mv ) to your repository on Daphne to manifest them. If you are unsure about a command, just check the Internet or ask in the course forum.

5 Linux Users If you are a Linux user, you probably know about installing software, e.g. via apt-get install. Usually Linux by default comes with Python 3, so you might just have to install pip (i.e. pip3 for Python 3), then via pip flake8, and of course subversion. Questions If you have any more questions, please post them in the course forum: