Week 5

Lecture

So this week was just a bit more on recursion. We learnt a bit more on how recursion works and how to trace through recursion functions step by step. Tracing isn’t one of my strongest points so it took a few examples before I got the hang of tracing through recursion code, but it was definitely challenging in a good way and an interesting learning process!

One of our tracing examples was:

def rec_max(L):

"""

Return the maximum number in possibly nested list of numbers.

>>> rec_max([17, 21, 0])

21

>>> rec_max([17, [21, 24], 0])

24

>>> rec_max([17, [21, 24], [18, 37, 16], 0])

37

"""

return max([rec_max(x) if isinstance(x, list) else x for x in L])

The point I started understanding how the tracing for recursion worked was when I figured out when exactly I had to start using the base case and then work backwards from it. It was frustrating at first, but it worked out in the end! Another useful technique was learning when I needed to just plug in values so I wasn’t tracing too much.

We also got a few examples with the Python visualizer, which definitely helped when it came to tracing through the recursion and understanding the step-by-step process of such functions. We even got a bit of help on the move_cheeses function for our Tower of Hanoi assignment which definitely helped as both a recursion example, and understanding how to make the code in our assignment more efficient.

Lastly, we also went through a few unittest examples so we had a better understanding on how it worked and how to use it.

Lab 4

I probably learnt the most in this lab than I have in any other lab, since this time we actually got to practice using recursion for the first time! Our first two exercises were tracing through recursion code with pencil and paper, which is pretty useful since our exam will be the same way. Also we had to make sure we were following one of the programming rules: being lazy! While tracing through code, we had to try and plug in values we’d worked out earlier to avoid tracing too much, a pretty useful trick in the Python programming world!

The rest of our exercises focused more on actually writing our own recursive functions, which was a bit daunting at first since I’d never done it before. Luckily, after figuring out what our base-case was, my partner and I found putting the rest of our function in a lot easier than we thought it would be. So I definitely learnt a lot from this week’s lab!

Assignment 1

Now for an assignment update! My partner and I are making pretty good progress with it so far! We’re almost completely done with step 4 of our Towers of Hanoi assignment. We’ve finished our TOAHModel.py file and it works great with GUIController (It’s actually pretty fun to play). The TOAHModel file seemed pretty challenging to finish at first, but as we went through it and the code got more familiar then it gradually got easier. Hopefully ConsoleController isn’t much harder, but since we’ve got most of our code in, it shouldn’t be too difficult. 

This assignment is definitely a lot more interesting than 108 assignments since it involves trying to work with different files and making sure they work together, and we have to write our own functions instead of them being half-done for us. Since it’s a game, it’s also a lot more fun!

That’s all for this week!