Pre-release-practice 2 (reaction times for students from Saturn and Mars)

prp2.py

# Pre-release practice 2
#
# Students are aged 12-16.
# Students belong to house Saturn or Mars.
#   We will represent that with "S" or "M".

ALLOWABLE_AGES = range(12,17)
ALLOWABLE_HOUSES = ["S", "M"]

# The program gets information from the user to store
#   - age             (integer)
#   - house           (string)
#   - reaction time   (float)
#
# There are 650 students in the school, so we will set up arrays of
# that length, plus 1 so we can index 1..650 instead of 0..649.
# Of course, we won't actually enter that much data.

SCHOOL_POPULATION = 650

AGE =   [None] * (SCHOOL_POPULATION + 1)
HOUSE = [None] * (SCHOOL_POPULATION + 1)
RTIME = [None] * (SCHOOL_POPULATION + 1)

# Returns four values:
#  * valid (True/False)  * age   * house   * reaction time
def input_single_student_data():
  age = int(input("Enter age (12-16): "))
  house = input("Enter house (S/M): ")
  rtime = float(input("Enter reaction time (sec): "))
  # Validate
  if age in ALLOWABLE_AGES and house in ALLOWABLE_HOUSES and rtime > 0:
    return (True, age, house, rtime)
  else:
    return (False, age, house, rtime)

# TASK 1: input and store records for a sample of students.
# Return the number of records stored.
def collect_input_data():
  # Find out how many records we are collecting.
  n = int(input("How many students? "))
  # Set an index to work towards that number.
  i = 1
  while i <= n:
    print("")
    print("Data for student", i)
    valid, age, house, rtime = input_single_student_data()
    if valid:
      # Store the data.
      AGE[i]   = age
      HOUSE[i] = house
      RTIME[i] = rtime
      # Increment the index.
      i = i + 1
    else:
      # Print error message.
      print("Invalid data; not stored.")
      # The index stays where it is.
  return n

# TASK 2: output house based statistics
# We run through the data, calculating the _sum_ and _count_ for
# both Saturn and Mars. Then display both averages.
# Parameter _n_ is the number of records stored.
def output_house_based_statistics(n):
  sum_saturn   = 0.0
  sum_mars     = 0.0
  count_saturn = 0
  count_mars   = 0

  # We look at every record from 0 to (n-1).
  for i in range(1, n+1):
    # Is the house Saturn or Mars?
    if HOUSE[i] == "S":
      count_saturn = count_saturn + 1
      sum_saturn   = sum_saturn + RTIME[i]
    else:
      count_mars   = count_mars + 1
      sum_mars     = sum_mars + RTIME[i]

  # Now we can display the averages. But check first that there are records.
  if count_saturn > 0:
    average = sum_saturn / count_saturn
    print("Average reaction time for Saturn:", average)
  else:
    print("No records for Saturn, so no average")

  if count_mars > 0:
    average = sum_mars / count_mars
    print("Average reaction time for Mars:", average)
  else:
    print("No records for Mars, so no average")

# TASK 3: output statistics based on user input
# Parameter _n_ is the number of records stored.
def output_selected_statistics(n):
  # Collect and validate the age and house.
  target_age   = int(input("Age:   "))
  target_house = input("House: ")
  if target_age in ALLOWABLE_AGES and target_house in ALLOWABLE_HOUSES:
    # We are calculating average and slowest reaction time.
    total = 0.0
    count = 0
    lowest = 1000000000000  # An impossibly high value, sure to be updated.
    # We look at every record from 0 to (n-1).
    for i in range(1, n+1):
      if AGE[i] == target_age and HOUSE[i] == target_house:
        count = count + 1
        total = total + RTIME[i]
        if RTIME[i] < lowest:
          # We have a new value for 'lowest'.
          lowest = RTIME[i]
    # We are now in a position to give the outputs desired.
    if count > 0:
      average = total / count
      print("Average reaction time (sec):", average)
      print("Lowest reaction time (sec): ", lowest)
    else:
      print("No records match your input")
  else:
    print("Invalid input(s).")

def program():
  # Task 1. The return value 'n' is the number of records stored.
  print("Task 1:Collecting input data")
  n = collect_input_data()
  # Task 2.
  print("")
  print("Task 2: Printing averges for each house")
  output_house_based_statistics(n)
  # Task 3.
  print("")
  print("Task 3: Printing selected statistics")
  output_selected_statistics(n)


# Run the program.
program()

Can I have a version of just the code to avoid confusion?