Mastering GUI Programming with Python

Updating the chart data

Our first step in updating our data is to create a method that calls psutil.cpu_percent() and updates the deque object:

    def refresh_stats(self):        usage = psutil.cpu_percent()        self.data.append(usage)

To update the chart, we only need to update the data in the series. There are a couple of ways to do this; for example, we could completely remove all the data in the chart and append() new values.

A better approach is to replace() the values, as follows:

        new_data = [            qtc.QPoint(x, y)            for x, y in enumerate(self.data)]        self.series.replace(new_data)

First, we generate a new set of QPoint objects from our deque object using a list comprehension, and then pass the list to the series object's replace() method, which swaps out ...