Configure Python web apps for IIS

When using Internet Information Services (IIS) as a web server on a Windows computer (including Windows virtual machines on Azure, Python apps must include specific settings in their web.config files so that IIS can properly process Python code. The computer itself must also have Python installed along with any packages the web app requires.

This article previously contained guidance for configuring Python on Azure App Service on Windows. The Python extensions and Windows hosts used in that scenario have been deprecated in favor of Azure App Service on Linux. For more information, see Publishing Python Apps to Azure App Service (Linux). The previous article, however, is still available on Managing App Service on Windows with the Python extensions.

Install Python on Windows

To run a web app, first install your required version of Python directly on the Windows host machine as described on Install Python interpreters.

Record the location of the python.exe interpreter for later steps. For convenience, you can add that location to your PATH environment variable.

Install packages

When using a dedicated host, you can use the global Python environment to run your app rather than a virtual environment. Accordingly, you can install all of your app’s requirements into the global environment simply by running pip install -r requirements.txt at a command prompt.

Set web.config to point to the Python interpreter

Your app’s web.config file instructs the IIS (7+) web server running on Windows about how it should handle Python requests through either HttpPlatform (recommended) or FastCGI. Visual Studio versions 2015 and earlier make these modifications automatically. When using Visual Studio 2017 and later, you must modify web.config manually.

Configure the HttpPlatform handler

The HttpPlatform module passes socket connections directly to a standalone Python process. This pass-through allows you to run any web server you like, but requires a startup script that runs a local web server. You specify the script in the element of web.config, where the processPath attribute points to the site extension’s Python interpreter and the arguments attribute points to your script and any arguments you want to provide:

The HTTP_PLATFORM_PORT environment variable shown here contains the port that your local server should listen on for connections from localhost. This example also shows how to create another environment variable, if desired, in this case SERVER_PORT .

Configure the FastCGI handler

FastCGI is an interface that works at the request level. IIS receives incoming connections and forwards each request to a WSGI app running in one or more persistent Python processes.

To use it, first install and configure the wfastcgi package as described on pypi.org/project/wfastcgi/.

Next, modify your app’s web.config file to include the full paths to python.exe and wfastcgi.py in the PythonHandler key. The steps below assume that Python is installed in c:\python36-32 and that your app code is in c:\home\site\wwwroot; adjust for your paths accordingly:

Modify the PythonHandler entry in web.config so that the path matches the Python install location (see IIS Configuration Reference (iis.net) for exact details).

• The value for PYTHONPATH may be freely extended but must include the root of your app.
• WSGI_HANDLER must point to a WSGI app importable from your app.
• WSGI_LOG is optional but recommended for debugging your app.

Set the WSGI_HANDLER entry in web.config as appropriate for the framework you’re using:

Bottle: make sure that you have parentheses after app.wsgi_app as shown below. This is necessary because that object is a function (see app.py) rather than a variable:

Flask: Change the WSGI_HANDLER value to

matches the name of your project. You can find the exact identifier by looking at the from

import app statement in the runserver.py. For example, if the project is named «FlaskAzurePublishExample», the entry would appear as follows:

Django: Two changes are needed to web.config for Django projects. First, change the WSGI_HANDLER value to django.core.wsgi.get_wsgi_application() (the object is in the wsgi.py file):

Second, add the following entry below the one for WSGI_HANDLER , replacing DjangoAzurePublishExample with the name of your project:

Django apps only: In the Django project’s settings.py file, add your site URL domain or IP address to ALLOWED_HOSTS as shown below, replacing ‘1.2.3.4’ with your URL or IP address, of course:

Failure to add your URL to the array results in the error DisallowedHost at / Invalid HTTP_HOST header: ‘ ‘. You may need to add ‘ ‘ to ALLOWED_HOSTS.

Get started using Python on Windows for beginners

The following is a step-by-step guide for beginners interested in learning Python using Windows 10.

Set up your development environment

For beginners who are new to Python, we recommend you install Python from the Microsoft Store. Installing via the Microsoft Store uses the basic Python3 interpreter, but handles set up of your PATH settings for the current user (avoiding the need for admin access), in addition to providing automatic updates. This is especially helpful if you are in an educational environment or a part of an organization that restricts permissions or administrative access on your machine.

If you are using Python on Windows for web development, we recommend a different set up for your development environment. Rather than installing directly on Windows, we recommend installing and using Python via the Windows Subsystem for Linux. For help, see: Get started using Python for web development on Windows. If you’re interested in automating common tasks on your operating system, see our guide: Get started using Python on Windows for scripting and automation. For some advanced scenarios (like needing to access/modify Python’s installed files, make copies of binaries, or use Python DLLs directly), you may want to consider downloading a specific Python release directly from python.org or consider installing an alternative, such as Anaconda, Jython, PyPy, WinPython, IronPython, etc. We only recommend this if you are a more advanced Python programmer with a specific reason for choosing an alternative implementation.

Install Python

To install Python using the Microsoft Store:

Go to your Start menu (lower left Windows icon), type «Microsoft Store», select the link to open the store.

Once the store is open, select Search from the upper-right menu and enter «Python». Open «Python 3.9» from the results under Apps. Select Get.

Once Python has completed the downloading and installation process, open Windows PowerShell using the Start menu (lower left Windows icon). Once PowerShell is open, enter Python —version to confirm that Python3 has installed on your machine.

The Microsoft Store installation of Python includes pip, the standard package manager. Pip allows you to install and manage additional packages that are not part of the Python standard library. To confirm that you also have pip available to install and manage packages, enter pip —version .

Install Visual Studio Code

By using VS Code as your text editor / integrated development environment (IDE), you can take advantage of IntelliSense (a code completion aid), Linting (helps avoid making errors in your code), Debug support (helps you find errors in your code after you run it), Code snippets (templates for small reusable code blocks), and Unit testing (testing your code’s interface with different types of input).

VS Code also contains a built-in terminal that enables you to open a Python command line with Windows Command prompt, PowerShell, or whatever you prefer, establishing a seamless workflow between your code editor and command line.

To install VS Code, download VS Code for Windows: https://code.visualstudio.com.

Once VS Code has been installed, you must also install the Python extension. To install the Python extension, you can select the VS Code Marketplace link or open VS Code and search for Python in the extensions menu (Ctrl+Shift+X).

Python is an interpreted language, and in order to run Python code, you must tell VS Code which interpreter to use. We recommend sticking with Python 3.7 unless you have a specific reason for choosing something different. Once you’ve installed the Python extension, select a Python 3 interpreter by opening the Command Palette (Ctrl+Shift+P), start typing the command Python: Select Interpreter to search, then select the command. You can also use the Select Python Environment option on the bottom Status Bar if available (it may already show a selected interpreter). 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.

To open the terminal in VS Code, select View > Terminal, or alternatively use the shortcut Ctrl+` (using the backtick character). The default terminal is PowerShell.

Inside your VS Code terminal, open Python by simply entering the command: python

Try the Python interpreter out by entering: print(«Hello World») . Python will return your statement «Hello World».

Install Git (optional)

If you plan to collaborate with others on your Python code, or host your project on an open-source site (like GitHub), VS Code supports version control with Git. The Source Control tab in VS Code tracks all of your changes and has common Git commands (add, commit, push, pull) built right into the UI. You first need to install Git to power the Source Control panel.

Download and install Git for Windows from the git-scm website.

An Install Wizard is included that will ask you a series of questions about settings for your Git installation. We recommend using all of the default settings, unless you have a specific reason for changing something.

If you’ve never worked with Git before, GitHub Guides can help you get started.

Hello World tutorial for some Python basics

Python, according to its creator Guido van Rossum, is a “high-level programming language, and its core design philosophy is all about code readability and a syntax which allows programmers to express concepts in a few lines of code.”

Python is an interpreted language. In contrast to compiled languages, in which the code you write needs to be translated into machine code in order to be run by your computer’s processor, Python code is passed straight to an interpreter and run directly. You just type in your code and run it. Let’s try it!

With your PowerShell command line open, enter python to run the Python 3 interpreter. (Some instructions prefer to use the command py or python3 , these should also work). You will know that you’re successful because a >>> prompt with three greater-than symbols will display.

There are several built-in methods that allow you to make modifications to strings in Python. Create a variable, with: variable = ‘Hello World!’ . Press Enter for a new line.

Print your variable with: print(variable) . This will display the text «Hello World!».

Find out the length, how many characters are used, of your string variable with: len(variable) . This will display that there are 12 characters used. (Note that the blank space it counted as a character in the total length.)

Convert your string variable to upper-case letters: variable.upper() . Now convert your string variable to lower-case letters: variable.lower() .

Count how many times the letter «l» is used in your string variable: variable.count(«l») .

Search for a specific character in your string variable, let’s find the exclamation point, with: variable.find(«!») . This will display that the exclamation point is found in the 11th position character of the string.

Replace the exclamation point with a question mark: variable.replace(«!», «?») .

To exit Python, you can enter exit() , quit() , or select Ctrl-Z.

Hope you had fun using some of Python’s built-in string modification methods. Now try creating a Python program file and running it with VS Code.

Hello World tutorial for using Python with VS Code

The VS Code team has put together a great Getting Started with Python tutorial walking through how to create a Hello World program with Python, run the program file, configure and run the debugger, and install packages like matplotlib and numpy to create a graphical plot inside a virtual environment.

Open PowerShell and create an empty folder called «hello», navigate into this folder, and open it in VS Code:

Once VS Code opens, displaying your new hello folder in the left-side Explorer window, open a command line window in the bottom panel of VS Code by pressing Ctrl+` (using the backtick character) or selecting View > Terminal. 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.

Continue the tutorial in the VS Code docs: Create a Python Hello World source code file.

Create a simple game with Pygame

Pygame is a popular Python package for writing games — encouraging students to learn programming while creating something fun. Pygame displays graphics in a new window, and so it will not work under the command-line-only approach of WSL. However, if you installed Python via the Microsoft Store as detailed in this tutorial, it will work fine.

Once you have Python installed, install pygame from the command line (or the terminal from within VS Code) by typing python -m pip install -U pygame —user .

Test the installation by running a sample game : python -m pygame.examples.aliens

All being well, the game will open a window. Close the window when you are done playing.

Here’s how to start writing your own game.

Open PowerShell (or Windows Command Prompt) and create an empty folder called «bounce». Navigate to this folder and create a file named «bounce.py». Open the folder in VS Code:

Using VS Code, enter the following Python code (or copy and paste it):

Save it as: bounce.py .

From the PowerShell terminal, run it by entering: python bounce.py .

Try adjusting some of the numbers to see what effect they have on your bouncing ball.

Read more about writing games with pygame at pygame.org.

Resources for continued learning

We recommend the following resources to support you in continuing to learn about Python development on Windows.

Online courses for learning Python

Introduction to Python on Microsoft Learn: Try the interactive Microsoft Learn platform and earn experience points for completing this module covering the basics on how to write basic Python code, declare variables, and work with console input and output. The interactive sandbox environment makes this a great place to start for folks who don’t have their Python development environment set up yet.

Python on Pluralsight: 8 Courses, 29 Hours: The Python learning path on Pluralsight offers online courses covering a variety of topics related to Python, including a tool to measure your skill and find your gaps.

LearnPython.org Tutorials: Get started on learning Python without needing to install or set anything up with these free interactive Python tutorials from the folks at DataCamp.

The Python.org Tutorials: Introduces the reader informally to the basic concepts and features of the Python language and system.

Learning Python on Lynda.com: A basic introduction to Python.

Working with Python in VS Code

Editing Python in VS Code: Learn more about how to take advantage of VS Code’s autocomplete and IntelliSense support for Python, including how to customize their behavior. or just turn them off.

Linting Python: Linting is the process of running a program that will analyse code for potential errors. Learn about the different forms of linting support VS Code provides for Python and how to set it up.

Debugging Python: Debugging is the process of identifying and removing errors from a computer program. This article covers how to initialize and configure debugging for Python with VS Code, how to set and validate breakpoints, attach a local script, perform debugging for different app types or on a remote computer, and some basic troubleshooting.

Unit testing Python: Covers some background explaining what unit testing means, an example walkthrough, enabling a test framework, creating and running your tests, debugging tests, and test configuration settings.