Stock Analysis using moving averages

stock_analysis.py

import matplotlib.pyplot as plt

"""
moving_average : list[float] int -> list[float]

Consumes a list of floats and computes the moving average with a window
    size of window_size

"""

def moving_average(a_list, window_size):
    ma = []
    if not len(a_list) % window_size == 0:
        return ma
    for i in range(window_size-1, len(a_list)):
        s = 0
        for j in range(0, window_size):
            s += a_list[i - window_size + 1 + j]
        ma.append(s/window_size)
    return ma

def intersects(y1, y2, y3, y4):
    return ((y3 < y1) and (y4 > y2)) or ((y3 > y1) and (y4 < y2))


def convert_stock_price(prices):
    return list(reversed(list(map(lambda x: float(x), prices.split('\n')[:-1]))))


def plot_stock_and_average(stock, m=5):
    prices = convert_stock_price(stock)
    length = len(prices)
    prices = prices[length%m:]
    ma = moving_average(prices, m)
    prices = prices[m-1:]
    print(len(ma))
    print(len(prices))
    plt.plot(prices)
    plt.plot(ma)
    plt.show()

def intersections(l1, l2):
    indexes = []
    way_intersects = []
    for i in range(len(l1) - 1):
        if intersects(l1[i], l1[i+1], l2[i], l2[i+1]):
            indexes.append(i)
            if intersects_above(l1[i], l1[i+1], l2[i], l2[i+1]):
                way_intersects.append('above')
            else:
                way_intersects.append('below')
    return (indexes, way_intersects)


def process_ma_signals(l1, l2):
    indexes, way_intersects = intersections(l1, l2)
    last_intersect_day = len(l1) - indexes[-1]
    last_intersect_way = way_intersects[-1]

    if last_intersect_way == 'above':
        return 'Last signal was a buy. It occured between ' + str(last_intersect_day - 1) + \
                ' and ' + str(last_intersect_day) + ' days ago'
    else:
        return 'Last signal was a sell. It occured between ' + str(last_intersect_day - 1) + \
                ' and ' + str(last_intersect_day) + ' days ago'

def intersects_above(y1, y2, y3, y4):
    return intersects(y1, y2, y3, y4) and y1 < y3 and y2 > y4

def intersects_below(y1, y2, y3, y4):
    return intersects(y1, y2, y3, y4) and y1 > y3 and y2 < y4


def stock_analysis(prices):
    stock = convert_stock_price(prices)
    stock = stock[len(stock)%5:]
    ma = moving_average(stock, 5)
    stock = stock[4:]
    s = process_ma_signals(stock, ma)
    print(s)
    plt.plot(stock)
    plt.plot(ma)
    plt.show()

def tests():
    assert moving_average([1, 2, 3, 4, 5], 5) == [3]
    assert moving_average([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 5) == [3, 4, 5, 6, 7, 8]
    assert moving_average([], 5) == []
    assert moving_average([1, 2, 3], 1) == [1, 2, 3]
    assert intersects(1, 3, 2, 1)
    assert intersects(1, 3, 0, 4)
    assert intersects(1, 3, 4, 5) == False
    print("All tests passed")


tests()