gistfile1.py

# This code is released into the public domain. License: Creative Commons Zero (CC0)

# person.py

import datetime

class Person(object):
    forenames = None
    surname = None
    maiden_name = None
    date_of_birth = None
    place_of_birth = None
    interests = []

    def describe_age(self):
        age = self.calculate_current_age()
        if age < 13:
            return "child"
        elif age < 20:
            return "teenager"
        else:
            return "adult"

    def add_interest(self, interest):
        self.interests.append(interest)

    def calculate_current_age(self):
        return (datetime.datetime.now() - self.date_of_birth).days / 365

# commandline.py

import sys
import datetime

def input_date(question):
    date_str = input(question + " (DD/MM/YYYY) ")
    return datetime.datetime.strptime(date_str, "%d/%m/%Y")

def set_basics():
    global person
    person.forenames = input("Forename(s): ")
    person.surname = input("Surname: ")
    maiden_name = input("Maiden Name: ")
    if len(maiden_name) > 0:
        person.maiden_name = maiden_name
    person.date_of_birth = input_date("Date of Birth: ")
    person.place_of_birth = input("Place of Birth: ")

def add_interest():
    global person
    person.add_interest(input("Interest: "))

def show_biography():
    print("Name: {person.forenames} {person.surname}".format(person=person))
    if person.maiden_name:
        print("Maiden Name: {person.maiden_name}".format(person=person))
    print("Born in {pob} on {dob}".format(dob=person.date_of_birth.strftime("%d/%m/%Y"),
                                          pob=person.place_of_birth))
    print("Currently {age} years old".format(age=person.calculate_current_age()))
    print("Interests include: ")
    for interest in person.interests:
        print(" - {interest}".format(interest=interest))

def show_help():
    for action_cmd, attributes in actions.items():
        print("Type {action} to {help}".format(action=action_cmd,
                                               help=attributes["help"]))

actions = {
    "setbasics":
        {
            "call": set_basics,
            "help": "set the basic details (name, age etc.)"
        },
    "addinterest":
        {
            "call": add_interest,
            "help": "add an interest (e.g. cooking or skateboarding)"
        },
    "showbio":
        {
            "call": show_biography,
            "help": "show the biography as it currently exists."
        },
    "help":
        {
            "call": show_help,
            "help": "show an explanation of how this programme works"
        },
    "close":
        {
            "call": sys.exit,
            "help": "close this programme"
        }
}

if __name__ == "__main__":
    person = Person()
    while True:
        try:
            action = actions[input(">>> ")]
            function = action["call"]
            function()
        except KeyError:
            print("Invalid command")
            show_help()

Line 13. Is that interest part called an array, which is used to store multiple values in one string?

 interests = [programming, music production, eating food]

put them in double quotes