Configuring a Development Environment

For this course we will all use the same software, namely Python, Git, and Visual Studio Code, so that we all have nearly the same experience, regardless of platform (Windows, macOS, Linux). We will also create a workspace on our computers for storing work, Python dependencies, software preferences, etc.; test out the creation of a virtual environment; and make sure it all works. Our goal by the end is to have a coding environment that enables a programmer’s workflow so we can learn to code efficiently and write programs that work.

Python

For running the code we write, we will need a Python interpreter. This is perhaps the most challenging to set up because each platform does it differently. Make sure you get Python version 3.7 or higher (3.11.1 is the highest stable version as of this writing). At the current time, NLTK requires Python versions 3.7, 3.8, 3.9 or 3.10. I recommend installing Python 3.10, since that’s what I’ll be working with.

Windows

The recommended way is to get the latest version from https://www.python.org: python-3.10.9-amd64.exe

During install, you should select “Add Python 3.10 to PATH”. If you do not, then later in the terminal you may need to use py instead of python or python3. That is, if these don’t work:

$ python --version
$ python3 --version

Try this instead (and let me know if this doesn’t work, either):

$ py --version

Whichever command returns you a version greater than or equal to 3.7 will be what you can use for this course.

See here for more information.

macOS

macOS machines come with Python 2.7, but this is an old and unsupported version that will not work for our class. The best way to install Python 3 is probably with Homebrew. First, start the Terminal app, and type the following at the prompt:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

This command will download the installer for Homebrew and then run it. Once it’s installed, run the following command in your terminal:

brew install python3

Some more information about installing Python with Homebrew is here.

Linux

Python 3 generally comes pre-installed on Linux. In a terminal, you can check the latest version of Python like this:

python3 --version

If it says “command ‘python3’ not found” or gives you a version lower than 3.7, you need to install a newer version. How this is done depends on the distribution of Linux, so contact me if you need help.

On some distributions, notably Ubuntu, you may need to install support for venv, which we use for creating virtual environments (described below). Here’s how you’d do that for Ubuntu:

sudo apt install python3-venv

Git

For tracking versions of the code we write, we will use Git. This is also how we will submit our homework assignments. Installation is straightforward but there are many options. Choose the default for all except for the editor, which may say “vim”. Choose “Visual Studio Code” instead.

If you haven’t already done so, go to Github and sign up for a free account with your email address. The email will be necessary for pushing changes to your assignments. Set up credentials on your local machine after installing Git with the commands below (replace USERNAME with your Github username, and NAME@EMAIL.com with your Github email address):

git config --global user.name "USERNAME"
git config --global user.email "NAME@EMAIL.com"

Windows

Download the latest version from https://git-scm.com: Git-2.39.0-64-bit.exe

macOS

Use Homebrew to install Git on macOS:

brew install git

Linux

Install with your package manager. Git’s website has instructions for many distributions: https://git-scm.com/download/linux

Visual Studio Code

Visual Studio Code is the program we use to write code. It also assists with running tests and tracking changes with Git, as well as other advanced features for developers, but we will not be exploring these for the most part.

For all platforms you can download an installer from https://code.visualstudio.com/.

Windows Download
macOS Download
Linux Download (.deb)

On macOS you can also use Homebrew, if you prefer:

brew install visual-studio-code

Visual Studio Code is quite capable on its own, but there are extensions that can make it even more useful for certain uses. I suggest only installing extensions from reputable sources, or those with many users and high ratings, as there’s the possibility of malicious extensions. I recommend the following for now:

Visual Studio Code may prompt you to install a “linter” for Python. This is optional, but it’s probably a good idea. It will let you know when you’ve made some kinds of programming mistakes.

Workspace

Now that the software is installed, we need a place to work in. This workspace is a folder (directory) somewhere on your computer (e.g., on the Desktop or whatever makes sense to you). Create it in whatever method you like (e.g., in Windows Explorer or Finder or in a terminal). For these instructions I will assume you named it “HG2051”. This also assumes that you know what folders are and how files/folders are organized on your computer. We will be going over the basics of this in the first week of class, but for now you should try to avoid folder names with spaces in them.

Once your folder is created, open Visual Studio Code and open the folder you just created via File > Open Folder. You will see something like this:

Empty HG2051 Workspace

Note the “Explorer” side bar (top-left), which is a file and folder view. It shows that you are in the “HG2051” folder. In the terminal panel (bottom-right), the prompt indicates the same thing, i.e., that you are in the “HG2051” folder. If you don’t see the terminal, try pressing Ctrl-`, or use the menu View > Terminal. Note that your prompt may look a bit different, depending on which shell and platform you’re using.

Virtual Environment

The next step here is to create a virtual environment, which is a subfolder that contains the Python packages we will use for this course. We will use one virtual environment for the whole course, though it is typical to use different environments for different projects.

Creating the Virtual Environment

Enter the following command into Visual Studio Code’s terminal (you may need to replace python3 with py on Windows):

python3 -m venv env

This calls the Python module venv, which creates virtual environments, and has it create one called “env” (you can name it whatever you like, but let’s stick with “env”). If successful, it will look like the following. If it did not succeed, please contact me.

Creating a Virtual Environment

Now notice in the Explorer side bar that the “env” folder is created. In the terminal, I also executed the ls command, which lists the contents of the current folder, showing that the “env” folder exists. You don’t need to worry about the contents of the “env” directory except for the following:

If you see a pop-up like the following (perhaps when editing a Python file), click “Yes” as it will help Visual Studio Code automatically run Python code using your virtual environment:

Auto-detection of a New Virtual Environment

You may get an error on Windows, though. For this, see below.

If you don’t see that, try opening the command palette and searching for “Python: Select Interpreter”. You should see an option for ./env/bin/python (macOS/Linux) or .\env\Scripts\python.exe (Windows). If not, enter or find the path appropriate for your platform.

Activating the Virtual Environment

Creating the virtual environment just makes a new folder and directories, but to use it you must activate it. An activated virtual environment directs Python to use the packages within the folder and not those installed elsewhere on your computer. Users on macOS or Linux can simply run the following command (and let me know if it doesn’t work):

source env/bin/activate

Windows users may have more work to do, because Windows by default blocks you from running “untrusted” scripts. First, we want to ensure that Windows PowerShell is being used as our default terminal in VSCode. We can do this by searching for terminal in the Command Palette ([Cmd]Ctrl-Shift-P) and selecting PowerShell as the default. Then, to allow the current session to activate the virtual environment, you can change Visual Studio Code’s settings so PowerShell can run these scripts. One thing to try is to open the settings by typing Ctrl-, or use the menu File > Preferences > Settings, then search for the following setting: terminal.integrated.shellArgs.windows

Finding the Setting

First select “User” so the change affects all your workspaces and not just the current folder. Then click on “Edit in settings.json” and change the value from the default of null to "-ExecutionPolicy ByPass":

Changing the Setting

Save the settings file and close. Since this is a setting that applies when a terminal is started and not one that is running, you will need to close the terminal (click the garbage bin icon), then start a new terminal. If that doesn’t work, try restarting Visual Studio Code. Now, in the new terminal, try to execute the following:

.\env\Scripts\Activate.ps1

If successful, you’ll see (env) at the beginning of the next prompt. If you see any errors, please let me know. While the environment is active, using python (instead of python3 or py) should use the Python version included in the virtual environment.

Thanks to the following Stack Overflow answer: https://stackoverflow.com/a/61281420/1441112

With newer versions of Windows, you may need to additionally disable the setting that tries to install Python from the Microsoft Store. You can do this by navigating to the ‘Apps and programs’ section of the settings page and deselecting the shortcut option there.

Another concern with Windows is that bash commands are not enabled by default in PowerShell, resulting in errors. The Bash program is installed by Git and used for committing and pushing changes, among other things. To ensure that bash commands are enabled, run the following command in your terminal:

$ set-ExecutionPolicy RemoteSigned -Scope CurrentUser

Thanks to THIS blog post and related Stack Overflow answer: https://stackoverflow.com/questions/1098786/run-bash-script-from-windows-powershell

Test It Out

If all was successful, you should be able to do the following two things.

Install the pytest Dependency

We will use pytest for automatic evaluation of some of our homework assignments. Once the virtual environment is active, run the following command:

pip install pytest

If it says the pip command is not found, ensure your virtual environment is active. If it is and still cannot find it, then try pip3 or python -m pip instead. If it still complains after that, then please contact me.

If it is successful, you’ll see 10 or so packages be installed in addition to pytest. The others are pytest’s dependencies.

Create a hello.py Module

Create a new file in Visual Studio Code (Ctrl-n or File > New File). Type the following into the file:

print('hello')

Then save (Ctrl-s or File > Save) the file to hello.py in your current workspace. Once it is saved, you should see the code become colored (syntax-highlighting). This means that Visual Studio Code recognized it as a Python file. If Visual Studio Code also detected your virtual environment, you should see a green “play” icon in the top right. Clicking that will launch a new terminal with the virtual environment active (the shell type will say “Python” instead of “bash” or “PowerShell”) and execute the Python file. You should see “hello” in the terminal output of the command.

Running hello.py

While it is nice to be able to use the “play” button to run a whole script or parts of the code from a script, our goal with this course is to learn how to create complete programs that run without errors. For this reason, you should avoid using the “play” button for the time being.

Workflow

The workflow we will follow makes use of three elements: the file explorer, the editor, and the terminal. You should become comfortable with moving between these elements as you develop your code. Your file explorer is where your programming files are located, along with various subfolders for organizational purposes. When you open a file to work on it, it opens in your editor, which allows you to write/modify code. After saving your work, you switch to the terminal to run the file and check that it functions. Going back and forth gives you immediate feedback and allows you to catch errors in order to fix them and achieve working code. For more details, a brief guide related to this course is provided in Using VS Code, with additional links to more comprehensive resources.