Скачать или смотреть How to Start a Flask Server with Python in an Efficient Way

Learn how to easily start your Flask server using a single Python script, eliminating the need for repetitive command line entries.
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This video is based on the question https://stackoverflow.com/q/68330095/ asked by the user 'Jannis' ( https://stackoverflow.com/u/15585864/ ) and on the answer https://stackoverflow.com/a/68330351/ provided by the user 'charchit' ( https://stackoverflow.com/u/15011621/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Starting Your Flask Server with a Single Python Command

If you've written a Flask application, you might know the common process to start your server. Typically, it involves navigating to your application directory, exporting the app, and finally running the Flask server. While this works perfectly, it can quickly become tedious to type these commands every time you want to start your application. Instead, wouldn't it be easier if you could start your Flask server with a simple Python script?

In this guide, we'll cover how to effectively set up your Flask server so that you can run it effortlessly.

The Traditional Method to Start a Flask Server

To start a Flask server, you usually go through these steps:

Navigate to your Project Directory

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Set the Flask App Environment Variable

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Run the Flask Application

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What Each Command Does:

cd /var/www/BWSWebApp: This command changes your current working directory to where your Flask application, main.py, is located.

export FLASK_APP=main.py: This sets an environment variable for Flask to know which application to run.

flask run --host=0.0.0.0: Runs the Flask application and makes it accessible to other devices on your network.

While this method works, retyping it every time can be cumbersome.

Automating the Process with Python

You might consider automating the startup process using a Python script, as follows:

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Why This Approach Doesn't Work

You might have tried the above code and noticed that it won't start the server. The issues are:

Commands in os.system(): Each command runs in a new shell, and the environment changes (like export FLASK_APP) are not retained across those shells.

No Output: Since the script executes and closes almost instantly, you'll also miss any output or logging from the server.

The Correct Solution: Using the App's run() Method

To effectively start and run your Flask application, you should modify your main.py file to include a specific conditional check using app.run(). Here’s how to do it:

Modifying main.py

Add the following code to your main.py:

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How This Works:

The above conditional ensures that app.run() only gets called when main.py is executed directly.

You can customize the run behavior with additional parameters. For example:

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Running Your Server

Now, to start your Flask application, you simply execute:

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This command will kick off your server effortlessly without the need for additional manual steps.

Conclusion

By modifying your main.py file and making use of app.run(), you can streamline the process of starting your Flask server. This not only saves time but also eliminates potential confusion with manual command entries. Now your Flask application can be up and running with a single command!

Happy coding!