Raymond Birthday Moving Average

.py

birthdays = [date(year=1990+x, month=2, day=18) for x in range(5000)]
def avg(birthdays):
    return float(len(birthdays)) / len([b for b in birthdays if b.weekday() == 6])

moving_avg = [avg(birthdays[:x]) for x in range(1, 5000)]
plt.plot(moving_avg)
plt.show()