def __get_percpu(self):
        """Update and/or return the per CPU list using the psutil library."""
        # Never update more than 1 time per cached_time
        if self.timer_percpu.finished():
            self.percpu_percent = []
            for cpu_number, cputimes in enumerate(psutil.cpu_times_percent(interval=0.0, percpu=True)):
                cpu = {'key': self.get_key(),
                       'cpu_number': cpu_number,
                       'total': round(100 - cputimes.idle, 1),
                       'user': cputimes.user,
                       'system': cputimes.system,
                       'idle': cputimes.idle}
                # The following stats are for API purposes only
                if hasattr(cputimes, 'nice'):
                    cpu['nice'] = cputimes.nice
                if hasattr(cputimes, 'iowait'):
                    cpu['iowait'] = cputimes.iowait
                if hasattr(cputimes, 'irq'):
                    cpu['irq'] = cputimes.irq
                if hasattr(cputimes, 'softirq'):
                    cpu['softirq'] = cputimes.softirq
                if hasattr(cputimes, 'steal'):
                    cpu['steal'] = cputimes.steal
                if hasattr(cputimes, 'guest'):
                    cpu['guest'] = cputimes.guest
                if hasattr(cputimes, 'guest_nice'):
                    cpu['guest_nice'] = cputimes.guest_nice
                # Append new CPU to the list
                self.percpu_percent.append(cpu)
                # Reset timer for cache
                self.timer_percpu = Timer(self.cached_time)
        return self.percpu_percent