Getting Started with Python in VS Code

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).

Note: You can use VS Code with Python 2 with this tutorial, but you need to make appropriate changes to the code.

Prerequisites

To successfully complete this tutorial, you must do the following:

  1. Install the Python extension for VS Code.

  2. Install a version of Python 3 (for which this tutorial is written). Options include:

    • (All operating systems) A download from python.org; typically use the Download Python 3.6.5 button that appears first on the page (or whatever is the latest version).
    • (Linux) The built-in Python 3 installation works well, but to install other Python packages you must run sudo apt install python3-pip in the terminal.
    • (MacOS) An installation through Homebrew on macOS using brew install python3 (the system install of Python on macOS is not supported).
    • (All operating systems) A download from Anaconda (for data science purposes).
  3. On Windows, make sure the location of your Python interpreter is included in your PATH environment variable. You can check this by running path at the command prompt. If the Python interpreter's folder isn't included, open Windows Settings, search for "environment", select Edit environment variables for your account, then edit the Path variable to include that folder.

Start VS Code in a project (workspace) folder

At 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:

mkdir hello
cd hello
code .

By starting VS Code in a folder, that folder becomes you "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.

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):

No interpreter selected

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

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, press the New File button on the hello folder:

File Explorer New File

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

File Explorer hello.py

By using the .py file extension, VS Code interprets this file as Python and evaluates the contents with the Python extension and the selected interpreter.

Next, start entering the following source code if using Python 3:

msg = "Hello World"
print(msg)

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

IntelliSense appearing for Python code

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 then you type msg.:

IntelliSense appearing for a variable whose type provides methods

Feel free to experiment with IntelliSense some more, but then revert 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. Right-click in the editor and select Run Python File in Terminal (which saves the file automatically):

Run Python File in Terminal command in the Python editor

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

Program output in a Python terminal

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

  • Select one or more lines, then press Shift+Enter or right-click and select Run Selection/Line in Python Terminal. This command is very convenient for testing just a part of a file.
  • Use the Python: Start REPL command to opens 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 left gutter next to the line numbers. A red circle appears in the gutter.

Setting a breakpoint in hello.py

Next, select the Debug View in the sidebar:

Debug icon

Then select the settings icon on the debug toolbar (or use the Debug > Open configurations menu command):

Debug toolbar settings command

The command opens a menu of available debuggers, which shows Python and Python Experimental. Select Python. The Python extension then creates a launch.json file that contains a number of configurations, which appear in the configurations drop-down:

Debug configurations after launch.json is created

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: Current File", which is the configuration that runs the current file shown in the editor using the currently selected Python interpreter.

To automatically stop the debugger on the first line when the program starts, add a "stopOnEntry": true setting to the "Python: Current File" configuration in launch.json, so that the whole configuration appears as follows:

{
    "name": "Python: Current File",
    "type": "python",
    "request": "launch",
    "program": "${file}",
    "stopOnEntry": true
},

Save launch.json, switch to hello.py in the editor, then run the debugger by selecting the green arrow in the Debug toolbar or pressing F5. Because stopOnEntry is set to true, the debugger stops on the first line of the file. The current line is indicated with a yellow arrow in the left margin. If you examine the Local variables window at this point, you see that only automatic dunder variables are defined:

Debugging step 1 - stop on entry

A debug toolbar appears along the top with the following commands from left to right: run (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)).

Debugging toolbar

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

To continue running the program, select the run command on the debug toolbar (F5) or the green arrow in the Debug view. The debugger runs the program to the next breakpoint. The now-defined msg variable appears in the Local pane

Debugging step 2 - variable defined

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:

msg
msg.capitalize()
msg.split()

Debugging step 3 - using the debug console

Select the green arrow again 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, remember that you set stopOnEntry in the configuration so that the debugger stops before running any code. To run all the way to the first breakpoint, remove that entry from the configuration.

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 Debug > Stop debugging menu command.

For full details, see Debugging configurations, which includes details on how to use a 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 if you choose the Python Experimental debugger. 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.

Troubleshooting

If for some reason VS Code doesn't generate launch.json for you, create a file by that name within the folder named .vscode folder (creating it if you need to), then paste the following contents into launch.json:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}"
        }
    ]
}

If you see "SyntaxError: invalid syntax" as shown below, you attempted to start to debugger when launch.json is currently showing in the editor, which is not Python code like hello.py:

    // Use IntelliSense to learn about possible attributes.
     ^
SyntaxError: invalid syntax

Select hello.py and try again. Alternately, create a debug configuration specifically for the hello.py file by adding the following lines in launch.json within the configuration array. Then select this configuration in the debugger drop-down and start the debugger again.

        {
            "name": "Python: hello.py",
            "type": "python",
            "request": "launch",
            "program": "hello.py"
        },

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 commonly done with data science.

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:

import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np

x = np.linspace(0, 20, 100)  # Create a list of evenly-spaced numbers over the range
plt.plot(x, np.sin(x))       # Plot the sine of each x point
plt.show()                   # Display the plot

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. (If you still have "stopOnEntry": true in that configuration, you need to select the run command again to continue.)

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), stop the debugger and run Python: Create Terminal from the Command Palette, which opens a command prompt for your selected interpreter. Then enter the following commands as appropriate for your operating system (commands may require elevation if the Python interpreter is installed in a protected area of the file system):

Note: If you are unable to install the package, please file an issue on GitHub so we can help you investigate.

# pip[3] install commands may require elevation

# macOS
pip3 install matplotlib

# Windows
pip install matplotlib

# Linux
sudo apt-get install python3-tk
pip3 install matplotlib

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

matplotlib output

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.

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

  • Python environments - Control which Python interpreter is used for editing and debugging.
  • 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.
  • Unit testing - Configure unit test environments and discover, run, and debug tests.
  • Settings reference - Explore the full range of Python-related settings in VS Code.