Summary: Environment Setup

Once the application loads successfully, we’re ready to move forward and start building the application. It is generally advised to keep the Parcel development web server (or later, the proxy web server) running while developing. It will automatically detect changes to the entry point file (in our case, app.py) and reload the application in the web browser for us. This speeds up the development loop quite a bit, even if we have to manually touch the app.py file (usually by just putting a space on an empty line) to trigger the application rebuild process by Parcel. It may seem a little inconvenient (and it is), but it is easier than manually stopping and restarting each time. The other benefit is that doing a full stop and restart rebuilds the entire application, but the automatic rebuild is incremental and only rebuilds what has actually changed, so it is much faster.

Important:

If the application doesn’t load, here are a few things to check:

• Check the code for syntax errors.
• Check the Parcel/Transcrypt build log for errors.
• Check the web browser developer console for errors.
• See if all of the files are loading successfully in the network tab of the web browser >console.
• Check to make sure that npm is working with npm -v to show the version.
• To start with a clean build slate, try deleting the .cache/, dist/, and src/__target__/ folders and rebuild the application.

What we learned