Lab 6: ToDo Manager

Overview

In this lab, you will practice using lists and strings in Python by implementing a very simple todo manager, which helps you keep track of a list of things to do (or a list of anything at all).

Here’s an example of what your program might look like by the end of the lab:

Welcome to the todo list manager!
Enter the name of the file with your todos: todo.txt
Warning, file todo.txt does not exist.
------------------------------
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 0
Enter the new todo: Finish writing todo manager lab
------------------------------
0) Finish writing todo manager lab
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 0
Enter the new todo: Revise paper
------------------------------
0) Finish writing todo manager lab
1) Revise paper
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 0
Enter the new todo: Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Finish writing todo manager lab
1) Revise paper
2) Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 2
0) Finish writing todo manager lab
1) Revise paper
2) Beat all MK8 Deluxe tracks on 200cc mode
Which todo do you want to replace? 1
Enter the new todo: Revise paper for JFP
------------------------------
0) Finish writing todo manager lab
1) Revise paper for JFP
2) Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 3
Enter the search string: z
No todos found matching 'z'.
------------------------------
0) Finish writing todo manager lab
1) Revise paper for JFP
2) Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 3
Enter the search string: t
Todos matching 't':
0) Finish writing todo manager lab
1) Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Finish writing todo manager lab
1) Revise paper for JFP
2) Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 1
0) Finish writing todo manager lab
1) Revise paper
2) Beat all MK8 Deluxe tracks on 200cc mode
Which todo do you want to remove? 0
------------------------------
0) Revise paper for JFP
1) Beat all MK8 Deluxe tracks on 200cc mode
------------------------------
0) Add a new todo
1) Remove a todo
2) Replace a todo
3) Search
4) Quit
Your choice? 4

Grading Criteria

  • A Complete submission includes:
    • All steps complete.
    • No Pycharm style warnings.

Step 1: Bits and Pieces

Create a new Python file called todo_manager.py, and put your name and date at the top.

Also add the line from typing import * right below the name and date.

Now follow the instructions below to write some functions you will need.

1.1 Turn a list into a string

Write a function called list_into_lines(items: List[str]) -> str.

Given a list of strings, this function should create a single string that combines all of the strings from the list, putting a newline character (\n) between each string. For example:

>>> list_into_lines(['red', 'yellow', 'blue'])
'red\nyellow\nblue'

You can also test your function like this:

>>> print(list_into_lines(['red', 'yellow', 'blue']))
red
yellow
blue

Hint: you should not need a while loop! It is possible to implement this function in only one line of code. Look at your notes from class!

1.2 Print Numbered List

Write a function called print_numbered_list(items: List[str]).

This function should take a list of strings as input and print them out, one per line, with numbers in front of them. For example, if given the list ['hat', 'socks', 'shoes'] as input, it should print out

0) hat
1) socks
2) shoes

Be sure to test your function by right-clicking and choosing “Run File in Console” and then trying your function with different inputs. For example, if you type

print_numbered_list(['hat', 'socks', 'shoes'])

at the prompt, you should see the output shown above.

1.3 Get choice

Write a function called get_choice(prompt: str, choices: List[str]) -> int.

This function takes as input a prompt string and a list of choices, and returns an int corresponding to the user’s choice. It should carry out the following steps:

  1. Print out a numbered list of the choices (using print_numbered_list).
  2. Prompt the user for input (using the provided prompt).
  3. Check to make sure the user’s input is a number, and if so, that it corresponds to one of the choices.
  4. If the user’s input is invalid, print an appropriate error message and simply return -1. Don’t use a while loop to re-prompt the user. This will allow the user to “cancel” by entering an invalid input.
  5. Otherwise, if the user entered a valid choice, return the number they chose (be sure to return an int, not a string!).

Again, you should be sure to load your file into the console and test it. For example, you might see something like this:

>>> get_choice("Whaddaya want? ", ['hat', 'socks', 'shoes'])
0) hat
1) socks
2) shoes
Whaddaya want? shirt
Sorry, shirt is not a number.
-1

>>> get_choice("What color elephant? ", ['grey', 'blue', 'red'])
0) grey
1) blue
2) red
What color elephant? 5
Sorry, 5 is not a valid choice.
-1

>>> get_choice("OK? ", ['sure', 'no way'])
0) sure
1) no way
OK? 1
1

Step 2: Loading and Saving

A todo list manager isn’t much good without being able to load and save lists of todos! You wouldn’t want to have to type in all your todos every time you run the program.

We have provided functions you can use to open and save text files. Later in the semester we will learn more about how they work. For now, you can just copy and paste these functions into your program.

# Open the file with the given name and return its contents as a list
# of strings, one per line; OR print a warning and return the empty
# list if there is an error opening the file (e.g. if the file does
# not exist).
def load_list_from_file(filename: str) -> List[str]:
    try:
        f = open(filename, 'r')
        lines = [l.rstrip() for l in f.readlines()]
        f.close()
        return lines
    except FileNotFoundError:
        print(f"Warning, file {filename} does not exist.")
        return []

# Write the given string to the file with the given name.
def save_file(filename: str, contents: str):
    try:
        f = open(filename, 'w')
        f.write(contents)
        f.close()
    except:
        print(f"Something went wrong saving {filename}!")

Now define a function main() which does the following:

  1. Prompt the user for the name of the file containing their todo list.
  2. Open the file (using the load_list_from_file function) and store the returned list in a variable.
  3. Add a fake todo item to the end of the list (this part is just temporary, to make sure everything else is working; you will remove it in the next step).
  4. Print out the todo list using print_numbered_list.
  5. Save the new, extended list back to the file using the save_file function (see the next paragraph for a helpful hint).

Note that save_file expects a string, not a list of strings, so you will have to call list_into_lines to turn your list of strings into a single string before calling it.

Again, you should be sure to test your main() function. (You can use whatever file name you want for your todo list; if it doesn’t already exist, it will be created by save_file.) You should be able to tell if the loading and saving is working since every time you run main() your todo list should have one additional item added to the end.

Step 3: Menu

Now we will modify your main() function so it lets the user repeatedly choose options from a menu.

First, create a list of strings representing the different menu choices that will be available to the user: there should be an option to add a todo, remove a todo, replace a todo, search for a todo, or quit.

Now, delete the code from main() thats adds a fake todo item to the end and prints the list (steps 3 and 4 above), and replace it with a loop:

  • The loop will exit when the user selects option 4.
  • At each iteration of the loop:
    • Using print_numbered_list, display the current todo list.
    • Using get_choice, request a menu option from the user, using the list of menu options you created earlier.

At this point the only active menu choice is the option to quit. Nothing will actually happen when you choose anything else from the menu; you will fix that in the next step.

Step 4: Operations

Now it’s time to actually implement the operations! Below are descriptions of what the different menu choices should do. You can also look at the example program output at the top of this lab for inspiration.

Be sure to test that each operation works before moving on to the next!

4.1 add

If the user chooses to add a new todo item, you should prompt them for a new todo and add it to the end of the list.

4.2 remove

If the user chooses to remove a todo item, you should use get_choice to ask for the index of the item they would like to remove. If get_choice returns -1, do nothing. Otherwise, you can use the pop list function to remove the item at a particular index, for example, if your list of todos is called todos and the user’s choice is stored in a variable called choice, you could write todos.pop(choice).

4.3 replace

This should work similarly to remove: ask the user which item they would like to replace; if they make a valid choice, prompt them for a new todo item, and replace the item at the index they chose. (Hint: replacing an item should be only one line of code! Look in your notes from class if you don’t remember how to do it.)

4.4 find_all()

Write a function

def find_all(term: str, items: List[str]) -> List[str]:

which takes a search term and a list of items, and returns the list of only those items from the list which contain the search term. You can check whether one string contains another string using the in operator: for example, "th" in "python" will return True, but "z" in "python" is False.

Test your function in the console: for example, you should get

>>> find_all("ab", ["baby", "dog", "cat", "absolute", "table", "python"])
["baby", "absolute", "table"]

Now implement the search menu choice: prompt the user what they want to search for, use find_all to get the todos that match their search term, and display them to the user using print_numbered_list.

At this point you should be able to reproduce something similar to the example program run shown at the beginning of the lab! Note, however, that your output does not need to be identical to the example shown. Feel free to use your creativity to make it look nice or add your own extra features.