main.py

import sys  # Needed to gracefully quit the Python app via "sys.exit".

__APP_NAME__ = "Pokémon Database"
__DEFAULT_DATABASE_FILE__ = "database.txt"

creatures = []  # We store all the Pokémon here.


def add_creature():
# Creates a new Pokémon based on user-given data, and adds it to the list.

    print("Adding a new Pokémon")

    creature = {}

    # The "ask" functions exist because this code is also used when editing a Pokémon's data.

    creature["id"] = ask_for_id()
    creature["name"] = ask_for_name()
    creature["type1"] = ask_for_primary_type()
    creature["type2"] = ask_for_secondary_type()
    creature["caught"] = ask_if_caught()

    creatures.append(creature)  # Append the new creature to the list of all creatures.

    print("Pokémon has been created and added to the in-memory database. Please remember to save your changes.\n")


def ask_for_id():
# Asks the user for a Pokémon's ID, and only accepts positive integers (> 0).

    while True:
        creature_id = input("ID: ").strip()  # Shouldn't use "id" in Python, thus this longer name.

        # This checks that the given value is a positive integer.
        try:
            id_for_check = int(creature_id)
            if id_for_check <= 0:
                print("Please give a positive integer.")
            else:
                break
        except ValueError:
            print("Please enter an integer.")

    return creature_id


def ask_for_string(prompt, fail_message, can_be_null=False):
# Asks the user for a string with the given prompt and fail message values, and returns that string.
# If the additional "can_be_null" argument is set to something else besides the default of False, this
# function skips the check for the input data (that it exists).

    while True:
        data = input(prompt + ": ").strip()

        if can_be_null:
            # The data can be empty, so we won't do the check. Any value will do here.
            break

        if not data:
            print(fail_message)
        else:
            break

    return data


def ask_for_name():
# A function that redirects to the "ask_for_string" -function, for the purpose of asking a Pokémon's name.

    return ask_for_string("Name", "Please enter a name for your Pokémon.")


def ask_for_primary_type():
# A function that redirects to the "ask_for_string" -function, for the purpose of asking a Pokémon's primary type.

    return ask_for_string("Main type", "Please enter a main (primary) type for the Pokémon.")


def ask_for_secondary_type():
# A function that redirects to the "ask_for_string" -function, for the purpose of asking a Pokémon's secondary type.
# The secondary type can be null (None), so the additional True parameter is passed. The second parameter is
# not used in this case, so it is passed as None.

    return ask_for_string("Secondary type (leave blank for none)", None, True)


def ask_if_caught():
# Asks the user if he/she has caught the Pokémon, and returns either a 'Y' or a 'N'.
#
# Used when creating a new Pokémon entry and when editing an existing Pokémon,
# that is why this function exists (to avoid DRY).

    while True:
        caught = input("Have you caught this Pokémon [Y/N]? ").strip().upper()
        if caught == "Y" or caught == "N":
            break
        else:
            print("Please either enter 'Y' for yes or 'N' for no.")

    return caught


def find_creature():
# Used to find a Pokémon, by ID or by name. Returns None if it can't find one.

    prompt = input("Please enter the Pokémon's name or ID: ").strip()
    creature = None
    try:
        creature_id = int(prompt)
        # This worked, so it is an integer (i.e., an ID).
        creature = find_creature_by_id(creature_id)
    except ValueError:
        # This did not work, so it must be the Pokémon's name.
        name = prompt
        creature = find_creature_by_name(name)

    return creature  # Returns the found Pokémon, or None.


def edit_creature():
# Edit's an existing Pokémon. The Pokémon's caught-status is changed elsewhere.

    print("Editing a Pokémon")

    creature = find_creature()

    if not creature:
        print("Could not find a Pokémon by that name or ID, so can't make changes to it.\n")
        return

    print("Current values: ID=" + creature["id"]
    + ", name=" + creature["name"]
    + ", type1=" + creature["type1"]
    + ", type2=" + creature["type2"])  # Display the current values of the Pokémon to the user.

    creature["id"] = ask_for_id()
    creature["name"] = ask_for_name()
    creature["type1"] = ask_for_primary_type()
    creature["type2"] = ask_for_secondary_type()

    print("Pokémon has been updated.\n")


def remove_creature():
# Removes a Pokémon from the database, if found.

    print("Removing a Pokémon")

    creature = find_creature()

    if not creature:
        print("Could not find a Pokémon by that name or ID, so can't remove it.\n")
        return

    creatures.remove(creature)

    print("Pokémon removed.\n")


def change_caught_status():
# Prompts for a Pokémon's caught-status, and updates it.

    creature = find_creature()

    if not creature:
        print("Could not find a Pokémon by that name or ID, so can't change its caught-status.\n")
        return

    creature["caught"] = ask_if_caught()

    print("The Pokémon's caught-status has been updated.\n")


def list_creatures():
# Lists all the Pokémon in the database.

    print("Listing Pokémon")

    if not creatures:
        print("No Pokémon in the database. Perhaps you'd like to load a database or add a new Pokémon?\n")
        return

    print("Would you like your Pokémon sorted by their ID (1), name (2), primary type (3) or secondary type (4)?")

    while True:
        choice = input("Please enter your choice: ")
        try:
            choice = int(choice)
            if choice < 1 or choice > 4:
                print("Please give a valid choice (1-4).")
            else:
                break

        except ValueError:
            print("That wasn't an integer.")

    new_list = []  # This is the new, sorted list.

    sort_string = "ID"

    if choice == 1:
        # We sort by ID (an integer).
        new_list = sorted(creatures, key = lambda k: int(k["id"]), reverse=False)
    else:
        # We sort by a string (not an integer).
        if choice == 2:
            sort_by = "name"
            sort_string = sort_by
        elif choice == 3:
            sort_by = "type1"
            sort_string = "primary type"
        else:
            sort_by = "type2"
            sort_string = "secondary type"

        new_list = sorted(creatures, key = lambda k: k[sort_by], reverse=False)

    print("Here are your Pokémon, sorted by " + sort_string + ": ")

    for creature in new_list:
        type_string = creature["type1"]
        if creature["type2"]:
            # If it has two types, they will be displayed nicely.
            type_string = type_string + " / " + creature["type2"]

        if creature["caught"] == "Y":
            caught = ", caught"
        else:
            caught = ", not caught yet"

        print(creature["id"] + ". " + creature["name"] + " (" + type_string + ")" + caught)

    print()  # A blank line is added here for readability.


def find_creature_by_name(name):
# Finds a Pokémon by name, returns None otherwise.

    for creature in creatures:
        if creature["name"].lower() == name.lower():
            return creature
    return None  # Strictly not required, here for clarity.


def find_creature_by_id(creature_id):
# Finds a Pokémon by ID, returns None otherwise.

    for creature in creatures:
        if int(creature["id"]) == creature_id:
            return creature
    return None  # Strictly not required, here for clarity.


def load_database():
# After the user has given the database file name, we'll loop through all rows and create new Pokémon based on them.

    file_name = input("Which database to load (default '" + __DEFAULT_DATABASE_FILE__ + "'): ").strip()

    if not file_name:
        file_name = __DEFAULT_DATABASE_FILE__

    try:
        file = open(file_name, "rt")  # Read, text.
    except IOError:
        print("Couldn't open that database.\n")
        return

    creatures.clear()  # We empty the existing data.

    for row in file:
        if row:  # Only for rows that actually contain data.
            data = row.split("|")  # Split based on the pipe ('|') character.
            creature = {}
            creature["id"] = data[0]
            creature["name"] = data[1]
            creature["type1"] = data[2]
            creature["type2"] = data[3]
            creature["caught"] = data[4].strip()  # This takes away the linefeed ("\n").

            creatures.append(creature)

    file.close()

    print("Database loaded successfully. " + str(len(creatures)) + " Pokémon are now in memory.\n")


def save_database():
# Here we ask the user for the database file name, and then save each Pokémon on its own row (entry).

    file_name = input("Where to save the database (default '" + __DEFAULT_DATABASE_FILE__ + "'): ").strip()

    if not file_name:
        file_name = __DEFAULT_DATABASE_FILE__

    try:
        file = open(file_name, "wt")  # Write, text.
    except IOError:
        print("Couldn't save to that database.\n")
        return

    for creature in creatures:
        entry = (creature["id"] + "|"
        + creature["name"] + "|"
        + creature["type1"] + "|"
        + creature["type2"] + "|"
        + creature["caught"] + "\n")  # Create the entries/rows.

        # Sample data:
        #
        # 1|Bulbasaur|Grass|Poison|N
        # 6|Charizard|Fire|Flying|N
        # 25|Pikachu|Electric||Y
        #
        # Each row contains exactly four (4) pipe characters, even if the space between them contains nothing.

        file.write(entry)  # Write the row.

    file.close()

    print("Database written successfully to '" + file_name + "'.\n")


def exit_app():
# This quits the app.

    print("Thanks for using the " + __APP_NAME__ + ". App terminated.\n")
    sys.exit()


def print_instructions():
# These instructions are printed when the app is first run, and subsequently only when requested.

    print("Please choose a command")
    print()  # To me, these are more readable than using "\n". Case-dependent, of course.
    print("A: Add a new Pokémon")
    print("R: Remove an existing Pokémon")
    print()
    print("E: Edit an existing Pokémon")
    print("C: Change Pokémon's caught-status")
    print()
    print("L: List all Pokémon (list order will be asked)")
    print()
    print("1: Load the database from an existing file (clears the memory)")
    print("2: Save the database to a file")
    print()
    print("3: Quit the app")
    print()


def loop_program():
# The main loop for the program. Will never end, unless explicitly asked to do so.

    command = input("Command ('X' for list of commands): ").strip().upper()  # We put it uppercase just in case.

    if command == "X":  # Print instructions for the user.
        print()
        print_instructions()
    elif command == "L":  # List all the Pokémon.
        print()
        list_creatures()
    elif command == "E":  # Edit Pokémon's data.
        print()
        edit_creature()
    elif command == "C":  # Change a Pokémon's caught-status.
        print()
        change_caught_status()
    elif command == "A":  # Add a new Pokémon.
        print()
        add_creature()
    elif command == "R":  # Remove an existing Pokémon.
        print()
        remove_creature()
    elif command == "1":  # Loads a database.
        print()
        load_database()
    elif command == "2":  # Saves the data into a database (new or existing).
        print()
        save_database()
    elif command == "3":  # Quits the app.
        print()
        exit_app()
    else:  # No valid command was entered.
        print()
        print("Unknown command. Type 'X' to see the list of available commands.\n")

# Here the app starts, after it has been defined in whole.

print("Welcome to the " + __APP_NAME__ + "!\n")
print_instructions()

while True:
    loop_program()