Page 105 - Beginning Programming with Pyth - John Paul Mueller

Defining the uses of checkpoints
Unlike many application saves, a checkpoint is an individual entry. Every time you create a checkpoint, you also create a hidden file. This file resides in a special folder of your project folder. For example, when looking at this book’s code, you find the checkpoints in the \BPPD\.ipynb_checkpoints folder. You can go back to this specific checkpoint later, if necessary, to turn back the clock of your development efforts. Checkpoint-type saves occur at these times:
Automatic: Notebook automatically creates a save for you every 120 seconds by default unless you change this interval using the %autosave magic function (see the “Using the Magic Functions” section of the chapter for details).
Manual checkpoint save: Generates a separate manually created save file.
All the save options use a single file. Consequently, each save overwrites the previous file. Any save is useful for general backup, ensuring that you have an alternative if an entity damages the original file between occurrences of major events (such as running or closing the application).
The manual checkpoint save helps you create a special kind of save. For example, you might get your application to a stable point at which everything runs, even if the application isn't feature complete. Consequently, you want to create a manual save, a checkpoint, to ensure that you can get back to this point should future edits cause application damage.
Checkpoints can also come in handy at other times. For example, you might add a risky feature to your application and want to protect the application against damage should the addition prove fatal. You use checkpoints whenever you want to be able to go back to a specific point in time during application development. It’s a kind of insurance that works in addition to automatic saves.