Calculating the maximum number of people alive at any given time

max_population.py

def max_popn_year(people):
  
    # initialize the lower and upper bounds
    lower_limit = float("INF")
    upper_limit = float("-INF")
    
    # Calculate the upper and lower bounds under consideration
    for person in people: 
        lower_limit = min(lower_limit, person.dob)
        upper_limit = max(upper_limit, person.dod) + 1 

    #Initialize population changes in an array
    popn_changes = [0] * (upper_limit - lower_limit)

    # Update the population change based on dob and dod
    for person in people:
        popn_changes[person.dob - lower_limit] += 1 
        popn_changes[person.dod - lower_limit] -= 1

    # initialize maximum population to 0 and population tracker to 0
    max_popn = 0
    population = 0
    
    for popn_change in popn_changes:
        population += popn_change
        max_popn = max(population, max_popn)
    
    return max_popn

  
#TEST
class Person:
    def __init__(self,  dob, dod):
        self.dob = dob
        self.dod = dod

P1 = Person(1960, 1980)
P2 = Person(1945, 1950)
P3 = Person(1965, 1987)
P4 = Person(1975, 1989)
P5 = Person(1945, 1976)
#4

people = [P1, P2, P3, P4, P5]

print(max_popn_year(people))