Moving average calculator

moving_average.py

from datetime import datetime
from random import randint

class MovAvgCalculator:

    def __init__(self, starting_list=None, window_duration=3600):
        self.moving_average = None
        if starting_list:
            self.my_list = starting_list
            self.sum = sum(starting_list)
            self.count = len(starting_list)
            self.calculate_average()
        else:
            self.my_list = []
            self.sum = 0
            self.count = 0
        self.window_duration = window_duration

    def update_window(self, new_items):
        self.add_new_items(new_items)
        self.remove_old_items()
        self.calculate_average()

    def add_new_items(self, new_items):
        for el_date, el_price in new_items:
            self.my_list.append((el_date, el_price))
            self.sum += el_price
            self.count += 1

    def remove_old_items(self):
        i = self.detect_old_items_idx()
        if i > 0:
            self.process_old_items(i)

    def process_old_items(self, idx):
        to_remove = self.my_list[:idx]
        for _, el_price in to_remove:
            self.count -= 1
            self.sum -= el_price

    def detect_old_items_idx(self):
        latest_date = self.my_list[-1][0]
        window_end = latest_date - self.window_duration
        i = 0
        el_date, el_price = self.my_list[i]
        while el_date < window_end:
            i += 1
            el_date, el_price = self.my_list[i]
        return i

    def generate_new_items(self):
        """
        Generating date/price tuples
        """
        count = randint(2, 10)
        new_prices = []
        last_date = self.get_last_timestamp()
        for i in range(count):
            new_el = randint(3000, 5000)
            el_date = last_date + randint(1, 10)
            new_prices.append((el_date, new_el))
        return new_prices

    def get_last_timestamp(self):
        if self.my_list:
            return self.my_list[-1][0]
        else:
            return datetime.now().timestamp()

    def calculate_average(self):
        self.moving_average = self.sum / self.count

if __name__ == '__main__':
    calc = MovAvgCalculator()
    new_price_points = calc.generate_new_items()
    calc.update_window(new_price_points)
    print(calc.moving_average)

To get this to work I needed to "pop" the remove items from the list. I suggest this modification:

def remove_old_items(self):
    i = self.detect_old_items_idx()
    if i > 0:
        self.process_old_items(i)
    while i > 0:
       self.my_list.pop(0)
       i=i-1