09-14

Ongoing topics

• Print vs return
• Mutation functions do not return values. Also: Why does append return None? Examples: append, extend. The Python boss post on the topic is short and informative.
• Copy vs in-place: sorted(data) vs data.sort().

Upcoming

• Changing the collecting while you iterate through it (copy instead)
• Using unittest to write “check-expects”.

Questions

1. Make a list of ten foods (allFoods). Make your own function someRand(data, N) to randomly select N items from a given list with replacement.

2. Randomly select 20 items from the list (with replacement) and use that as foodList for the next problems.

3. Make a list of ordered pairs (food, number of that food in foodList) so that every possible food appears once.

4. Create a dictionary foodCount with the same information as the previous problem. That is foodCount[food] is the number of that food in foodList.

5. Create a function randomCap that takes in a string and puts out a string with a random capitalization, one of three cases: lower(), upper() and title().

6. Use your function to make a new variable foodListCaps by applying randomCap to foodList.

7. Sort foodListCaps and print it out.

8. Sort it again, but in a way that ignores the case of the letters. Print that out too.

9. Write a function del37 that deletes the items in indices 3 through 7 from a given input list. Verify that it works:

    squares20 = [ x*x for x in range(15) ]
    del37(squares20)
    print(squares20)
   

10. Make a set containing every food in foodList.

11. Write a function that takes in a string and returns a set of all of the non-vowels in the string. Test it on your name.

Problems

Everyone does the first one. If you want to skip the questions above, do the second one.

• USACO 2019 January Bronze 1: shell game.

• USACO 2018 December Bronze 3: back and forth.

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