How to Pause Code Execution in Jupyter Notebook with Widgets

Learn how to effectively pause code execution in Jupyter Notebook using ipywidgets and avoid CPU overload with a simple sleep method.
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How to Pause Code Execution in Jupyter Notebook with Widgets

Are you developing a Python project in Jupyter Notebook and need a way to pause the code execution until a button is clicked? If so, you’re not alone! Many developers encounter similar challenges when integrating interactive features in their Jupyter environment. In this guide, we'll explore a straightforward solution to this issue using ipywidgets.

The Problem: Pausing Execution Until a Button is Clicked

With Jupyter Notebooks, you might want to run specific pieces of code only after receiving input from the user, such as clicking a button. In the provided example, there’s a Submit answer button that evaluates user selections made through radio buttons ('Valid', 'Invalid', 'Skip'). However, the challenge arises when you want subsequent code to execute only after the button is pressed.

Here’s the initial snippet of code:

[[See Video to Reveal this Text or Code Snippet]]

In this code, executing print('nvm') will occur immediately after the widgets.HBox calls, regardless of whether the submit button has been clicked or not.

The Solution: Using a Sleep Loop

To ensure that specific code only runs after the button has been clicked, we can use a sleep loop. This involves creating a condition to keep the script in a waiting state until the button is pressed. Here's how you can do it:

Step 1: Set Up a Condition Variable

First, we need a variable to flag when the button has been clicked:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Modify the Button Callback Function

Next, we can modify the evaluate function. We will update the answer_pressed flag when the button is clicked:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Implement the Sleep Loop

Finally, we implement a simple loop that will keep the interpreter asleep until the button has been clicked:

[[See Video to Reveal this Text or Code Snippet]]

Complete Code Example

Below is how the full code would look after making these adjustments:

[[See Video to Reveal this Text or Code Snippet]]

A Quick Note

There's an important edit to consider: You might want to move the line answer_pressed = True to the end of the evaluate function. This way, you ensure that the entire function logic has executed before exiting the loop.

Conclusion

Pausing code execution in Jupyter Notebook with interactive widgets can be easily managed using a sleep loop approach. By implementing this method, you maintain control over code execution flow while avoiding heavy CPU loads that can occur from infinite loops.

Feel free to experiment with different configurations and adapt the approach to fit your project requirements!