In this tutorial, you use Python 3 to create the simplest Python 'Hello World' application in Visual Studio Code. By using the Python extension, you make VS Code into a great lightweight Python IDE (which you may find a productive alternative to PyCharm).

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This tutorial introduces you to VS Code as a Python environment, primarily how to edit, run, and debug code through the following tasks:

• Write, run, and debug a Python 'Hello World' Application
• Learn how to install packages by creating Python virtual environments
• Write a simple Python script to plot figures within VS Code

This tutorial is not intended to teach you Python itself. Once you are familiar with the basics of VS Code, you can then follow any of the programming tutorials on python.org within the context of VS Code for an introduction to the language.

If you have any problems, feel free to file an issue for this tutorial in the VS Code documentation repository.

Note: You can use VS Code with Python 2 with this tutorial, but you need to make appropriate changes to the code, which are not covered here.

Prerequisites

To successfully complete this tutorial, you need to first setup your Python development environment. Specifically, this tutorial requires:

• VS Code
• VS Code Python extension
• Python 3

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Install Visual Studio Code and the Python Extension

1. If you have not already done so, install VS Code.

2. Next, install the Python extension for VS Code from the Visual Studio Marketplace. For additional details on installing extensions, see Extension Marketplace. The Python extension is named Python and it's published by Microsoft.

Install a Python interpreter

Along with the Python extension, you need to install a Python interpreter. Which interpreter you use is dependent on your specific needs, but some guidance is provided below.

Windows

Install Python from python.org. You can typically use the Download Python button that appears first on the page to download the latest version.

Note: If you don't have admin access, an additional option for installing Python on Windows is to use the Microsoft Store. The Microsoft Store provides installs of Python 3.7 and Python 3.8. Be aware that you might have compatibility issues with some packages using this method.

For additional information about using Python on Windows, see Using Python on Windows at Python.org

macOS

The system install of Python on macOS is not supported. Instead, an installation through Homebrew is recommended. To install Python using Homebrew on macOS use brew install python3 at the Terminal prompt.

Note On macOS, make sure the location of your VS Code installation is included in your PATH environment variable. See these setup instructions for more information.

Linux

The built-in Python 3 installation on Linux works well, but to install other Python packages you must install pip with get-pip.py.

Other options

• Data Science: If your primary purpose for using Python is Data Science, then you might consider a download from Anaconda. Anaconda provides not just a Python interpreter, but many useful libraries and tools for data science.

• Windows Subsystem for Linux: If you are working on Windows and want a Linux environment for working with Python, the Windows Subsystem for Linux (WSL) is an option for you. If you choose this option, you'll also want to install the Remote - WSL extension. For more information about using WSL with VS Code, see VS Code Remote Development or try the Working in WSL tutorial, which will walk you through setting up WSL, installing Python, and creating a Hello World application running in WSL.

Verify the Python installation

To verify that you've installed Python successfully on your machine, run one of the following commands (depending on your operating system):

• Linux/macOS: open a Terminal Window and type the following command:

• Windows: open a command prompt and run the following command:

If the installation was successful, the output window should show the version of Python that you installed.

Note You can use the py -0 command in the VS Code integrated terminal to view the versions of python installed on your machine. The default interpreter is identified by an asterisk (*).

Start VS Code in a project (workspace) folder

Using a command prompt or terminal, create an empty folder called 'hello', navigate into it, and open VS Code (code) in that folder (.) by entering the following commands:

Note: If you're using an Anaconda distribution, be sure to use an Anaconda command prompt.

By starting VS Code in a folder, that folder becomes your 'workspace'. VS Code stores settings that are specific to that workspace in .vscode/settings.json, which are separate from user settings that are stored globally.

Alternately, you can run VS Code through the operating system UI, then use File > Open Folder to open the project folder.

Select a Python interpreter

Python is an interpreted language, and in order to run Python code and get Python IntelliSense, you must tell VS Code which interpreter to use.

From within VS Code, select a Python 3 interpreter by opening the Command Palette (⇧⌘P (Windows, Linux Ctrl+Shift+P)), start typing the Python: Select Interpreter command to search, then select the command. You can also use the Select Python Environment option on the Status Bar if available (it may already show a selected interpreter, too):

The command presents a list of available interpreters that VS Code can find automatically, including virtual environments. If you don't see the desired interpreter, see Configuring Python environments.

Note: When using an Anaconda distribution, the correct interpreter should have the suffix ('base':conda), for example Python 3.7.3 64-bit ('base':conda).

Selecting an interpreter sets the python.pythonPath value in your workspace settings to the path of the interpreter. To see the setting, select File > Preferences > Settings (Code > Preferences > Settings on macOS), then select the Workspace Settings tab.

Note: If you select an interpreter without a workspace folder open, VS Code sets python.pythonPath in your user settings instead, which sets the default interpreter for VS Code in general. The user setting makes sure you always have a default interpreter for Python projects. The workspace settings lets you override the user setting.

Create a Python Hello World source code file

From the File Explorer toolbar, select the New File button on the hello folder:

Name the file hello.py, and it automatically opens in the editor:

By using the .py file extension, you tell VS Code to interpret this file as a Python program, so that it evaluates the contents with the Python extension and the selected interpreter.

Note: The File Explorer toolbar also allows you to create folders within your workspace to better organize your code. You can use the New folder button to quickly create a folder.

Now that you have a code file in your Workspace, enter the following source code in hello.py:

When you start typing print, notice how IntelliSense presents auto-completion options.

IntelliSense and auto-completions work for standard Python modules as well as other packages you've installed into the environment of the selected Python interpreter. It also provides completions for methods available on object types. For example, because the msg variable contains a string, IntelliSense provides string methods when you type msg.:

Feel free to experiment with IntelliSense some more, but then revert your changes so you have only the msg variable and the print call, and save the file (⌘S (Windows, Linux Ctrl+S)).

For full details on editing, formatting, and refactoring, see Editing code. The Python extension also has full support for Linting.

Run Hello World

It's simple to run hello.py with Python. Just click the Run Python File in Terminal play button in the top-right side of the editor.

The button opens a terminal panel in which your Python interpreter is automatically activated, then runs python3 hello.py (macOS/Linux) or python hello.py (Windows):

There are three other ways you can run Python code within VS Code:

• Right-click anywhere in the editor window and select Run Python File in Terminal (which saves the file automatically):

• Select one or more lines, then press Shift+Enter or right-click and select Run Selection/Line in Python Terminal. This command is convenient for testing just a part of a file.

• From the Command Palette (⇧⌘P (Windows, Linux Ctrl+Shift+P)), select the Python: Start REPL command to open a REPL terminal for the currently selected Python interpreter. In the REPL, you can then enter and run lines of code one at a time.

Configure and run the debugger

Let's now try debugging our simple Hello World program.

First, set a breakpoint on line 2 of hello.py by placing the cursor on the print call and pressing F9. Alternately, just click in the editor's left gutter, next to the line numbers. When you set a breakpoint, a red circle appears in the gutter.

Next, to initialize the debugger, press F5. Since this is your first time debugging this file, a configuration menu will open from the Command Palette allowing you to select the type of debug configuration you would like for the opened file.

Note: VS Code uses JSON files for all of its various configurations; launch.json is the standard name for a file containing debugging configurations.

These different configurations are fully explained in Debugging configurations; for now, just select Python File, which is the configuration that runs the current file shown in the editor using the currently selected Python interpreter.

The debugger will stop at the first line of the file breakpoint. The current line is indicated with a yellow arrow in the left margin. If you examine the Local variables window at this point, you will see now defined msg variable appears in the Local pane.

A debug toolbar appears along the top with the following commands from left to right: continue (F5), step over (F10), step into (F11), step out (⇧F11 (Windows, Linux Shift+F11)), restart (⇧⌘F5 (Windows, Linux Ctrl+Shift+F5)), and stop (⇧F5 (Windows, Linux Shift+F5)).

The Status Bar also changes color (orange in many themes) to indicate that you're in debug mode. The Python Debug Console also appears automatically in the lower right panel to show the commands being run, along with the program output.

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To continue running the program, select the continue command on the debug toolbar (F5). The debugger runs the program to the end.

Tip Debugging information can also be seen by hovering over code, such as variables. In the case of msg, hovering over the variable will display the string Hello world in a box above the variable.

You can also work with variables in the Debug Console (If you don't see it, select Debug Console in the lower right area of VS Code, or select it from the .. menu.) Then try entering the following lines, one by one, at the > prompt at the bottom of the console:

Select the blue Continue button on the toolbar again (or press F5) to run the program to completion. 'Hello World' appears in the Python Debug Console if you switch back to it, and VS Code exits debugging mode once the program is complete.

If you restart the debugger, the debugger again stops on the first breakpoint.

To stop running a program before it's complete, use the red square stop button on the debug toolbar (⇧F5 (Windows, Linux Shift+F5)), or use the Run > Stop debugging menu command.

For full details, see Debugging configurations, which includes notes on how to use a specific Python interpreter for debugging.

Tip: Use Logpoints instead of print statements: Developers often litter source code with print statements to quickly inspect variables without necessarily stepping through each line of code in a debugger. In VS Code, you can instead use Logpoints. A Logpoint is like a breakpoint except that it logs a message to the console and doesn't stop the program. For more information, see Logpoints in the main VS Code debugging article.

Install and use packages

Let's now run an example that's a little more interesting. In Python, packages are how you obtain any number of useful code libraries, typically from PyPI. For this example, you use the matplotlib and numpy packages to create a graphical plot as is commonly done with data science. (Note that matplotlib cannot show graphs when running in the Windows Subsystem for Linux as it lacks the necessary UI support.)

Return to the Explorer view (the top-most icon on the left side, which shows files), create a new file called standardplot.py, and paste in the following source code:

Tip: If you enter the above code by hand, you may find that auto-completions change the names after the as keywords when you press Enter at the end of a line. To avoid this, type a space, then Enter.

Next, try running the file in the debugger using the 'Python: Current file' configuration as described in the last section.

Unless you're using an Anaconda distribution or have previously installed the matplotlib package, you should see the message, 'ModuleNotFoundError: No module named 'matplotlib'. Such a message indicates that the required package isn't available in your system.

To install the matplotlib package (which also installs numpy as a dependency), stop the debugger and use the Command Palette to run Terminal: Create New Integrated Terminal (⌃⇧` (Windows, Linux Ctrl+Shift+`)). This command opens a command prompt for your selected interpreter.

A best practice among Python developers is to avoid installing packages into a global interpreter environment. You instead use a project-specific virtual environment that contains a copy of a global interpreter. Once you activate that environment, any packages you then install are isolated from other environments. Such isolation reduces many complications that can arise from conflicting package versions. To create a virtual environment and install the required packages, enter the following commands as appropriate for your operating system:

Note: For additional information about virtual environments, see Environments.

1. Create and activate the virtual environment

   Note: When you create a new virtual environment, you should be prompted by VS Code to set it as the default for your workspace folder. If selected, the environment will automatically be activated when you open a new terminal.

   For windows

   If the activate command generates the message 'Activate.ps1 is not digitally signed. You cannot run this script on the current system.', then you need to temporarily change the PowerShell execution policy to allow scripts to run (see About Execution Policies in the PowerShell documentation):

   For macOS/Linux

2. Select your new environment by using the Python: Select Interpreter command from the Command Palette.

3. Install the packages

4. Rerun the program now (with or without the debugger) and after a few moments a plot window appears with the output:

5. Once you are finished, type deactivate in the terminal window to deactivate the virtual environment.

For additional examples of creating and activating a virtual environment and installing packages, see the Django tutorial and the Flask tutorial.

Next steps

You can configure VS Code to use any Python environment you have installed, including virtual and conda environments. You can also use a separate environment for debugging. For full details, see Environments.

To learn more about the Python language, follow any of the programming tutorials listed on python.org within the context of VS Code.

To learn to build web apps with the Django and Flask frameworks, see the following tutorials:

There is then much more to explore with Python in Visual Studio Code:

• Editing code - Learn about autocomplete, IntelliSense, formatting, and refactoring for Python.
• Linting - Enable, configure, and apply a variety of Python linters.
• Debugging - Learn to debug Python both locally and remotely.
• Testing - Configure test environments and discover, run, and debug tests.
• Settings reference - Explore the full range of Python-related settings in VS Code.

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This walkthrough illustrates how to use a data source defined in an app.config file for unit testing. You will learn how to create an app.config file that defines a data source that can be used by the DataSourceAttribute class. Tasks presented in this walkthrough include the following:

• Creating an app.config file.

• Defining a custom configuration section.

• Defining connection strings.

• Defining the data sources.

• Accessing the data sources using the DataSourceAttribute class.

Prerequisites

To complete this walkthrough, you need:

• Visual Studio Enterprise

• Either Microsoft Access or Microsoft Excel to provide data for at least one of the test methods.

• A Visual Studio solution that contains a test project.

Add an app.config file to the project

1. If your test project already has an app.config file, go to Define a custom configuration section.

2. Right-click your test project in Solution Explorer, and then select Add > New Item.

   The Add New Item window opens.

3. Select the Application Configuration File template and click Add.

Define a custom configuration section

Examine the app.config file. It contains at least the XML declaration and a root element.

To add the custom configuration section to the app.config file

1. The root element of app.config should be the configuration element. Create a configSections element within the configuration element. The configSections should be the first element in the app.config file.

2. Within the configSections element, create a section element.

3. In the section element, add an attribute called name and assign it a value of microsoft.visualstudio.testtools. Add another attribute called type and assign it a value of Microsoft.VisualStudio.TestTools.UnitTesting.TestConfigurationSection, Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions.

The section element should look similar to this:

Note

The assembly name must match the version that you are using.

Define connection strings

The connection strings define provider-specific information for accessing data sources. Connection strings defined in configuration files provide reusable data provider information across an application. In this section, you create two connection strings that will be used by data sources that are defined in the Custom Configuration Section.

To define connection strings

1. After the configSections element, create a connectionStrings element.

2. Within the connectionStrings element, create two add elements.

3. In the first add element, create the following attributes and values for a connection to a Microsoft Access database:

Attribute	Values
name	'MyJetConn'
connectionString	'Provider=Microsoft.Jet.OLEDB.4.0; Data Source=C:testdatasource.accdb; Persist Security Info=False;'
providerName	'System.Data.OleDb'

In the second add element, create the following attributes and values for a connection to a Microsoft Excel spreadsheet:

Attribute	Values
name	'MyExcelConn'
connectionString	'Dsn=Excel Files;dbq=data.xlsx;defaultdir=.; driverid=790;maxbuffersize=2048;pagetimeout=5'
providerName	'System.Data.Odbc'

The connectionStrings element should look similar to this:

Define data sources

The data sources section contains four attributes that are used by the test engine to retrieve data from a data source.

• name defines the identity used by the DataSourceAttribute to specify which data source to use.

• connectionString identifies the connection string created in the previous Define Connection Strings section.

• dataTableName defines the table or sheet that holds the data to use in the test.

• dataAccessMethod defines the technique for accessing data values in the data source.

In this section, you'll define two data sources to use in a unit test.

To define data sources

1. After the connectionStrings element, create a microsoft.visualstudio.testtools element. This section was created in Define a Custom Configuration Section.

2. Within the microsoft.visualstudio.testtools element, create a dataSources element.

3. Within the dataSources element, create two add elements.

4. In the first add element, create the following attributes and values for a Microsoft Access data source:

Attribute	Values
name	'MyJetDataSource'
connectionString	'MyJetConn'
dataTableName	'MyDataTable'
dataAccessMethod	'Sequential'

In the second add element, create the following attributes and values for a Microsoft Excel data source:

Attribute	Values
Name	'MyExcelDataSource'
connectionString	'MyExcelConn'
dataTableName	'Sheet1$'
dataAccessMethod	'Sequential'

The microsoft.visualstudio.testtools element should look similar to this:

The final app.config file should look similar to this:

Create a unit test that uses data sources defined in app.config

Now that an app.config file has been defined, you will create a unit test that uses data located in the data sources that are defined in the app.config file. In this section, we will:

• Create the data sources found in the app.config file.

• Use the data sources in two test methods that compare the values in each data source.

To create a Microsoft Access data source

1. Create a Microsoft Access database named testdatasource.accdb.

2. Create a table and name it MyDataTable in testdatasource.accdb.

3. Create two fields in MyDataTable named Arg1 and Arg2 using the Number data type.

4. Add five entities to MyDataTable with the following values for Arg1 and Arg2, respectively: (10,50), (3,2), (6,0), (0,8) and (12312,1000).

5. Save and close the database.

6. Change the connection string to point to the location of the database. Change the value of Data Source to reflect the location of the database.

To create a Microsoft Excel data source

1. Create a Microsoft Excel spreadsheet named data.xlsx.

2. Create a sheet named Sheet1 if it does not already exist in data.xlsx.

3. Create two column headers and name them Val1 and Val2 in Sheet1.

4. Add five entities to Sheet1 with the following values for Val1 and Val2, respectively: (1,1), (2,2), (3,3), (4,4) and (5,0).

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5. Save and close the spreadsheet.

6. Change the connection string to point to the location of the spreadsheet. Change the value of dbq to reflect the location of the spreadsheet.

To create a unit test using the app.config data sources

1. Add a unit test to the test project.

2. Replace the auto-generated contents of the unit test with the following code:

3. Examine the DataSource attributes. Notice the setting names from the app.config file.

4. Build your solution and run MyTestMethod and MyTestMethod2 tests.

Important

Deploy items like data sources so that they are accessible to the test in the deployment directory.

See also