winterthunder: (Default)
Amazing Little Ecosystem ([personal profile] winterthunder) wrote in [community profile] intro_to_cs2010-01-10 04:43 pm

Lecture 2

All right! Hopefully we've all successfully completed Problem Set 0 and are ready to tackle Lecture 2. Note that there is a handout associated with this lecture, and having it printed out before starting is a really helpful thing. Not that I had to stop and print it in the middle of lecture or anything...

Also, since our problem set numbers started with 0, I'm going to put up a post for PS1 this Friday. From that point on, problem sets will go up every other week.







I had one problem with this lecture, and I'm hoping you all can facilitate a light bulb moment. The code example with x, y and z, the fourth one down the page... I can't figure out what the bug was. Is it just because the statements aren't indented, or is there something else?
zulu: Hugh Laurie as House, with text: seeker after truth (house - truth seeker)

[personal profile] zulu 2010-01-10 10:05 pm (UTC)(link)
I'm not sure where the handout is, so this is just a guess, but maybe the bug is that there's no colon after the first instruction? For instance, this is correnct:

if x > y:
     print x

But this is not correct:

if x > y
     print x
afuna: Cat under a blanket. Text: "Cats are just little people with Fur and Fangs" (Default)

[personal profile] afuna 2010-01-17 02:37 pm (UTC)(link)
Oh goodness, thanks for that. I've been having a hard time making out some of the code examples; forgot it was in the handouts. This should make things easier :)
jetamors: Yoruichi is really hot (Default)

[personal profile] jetamors 2010-01-10 11:23 pm (UTC)(link)
C&Ping the code to make it clearer:

x = 15
y = 5
z = 11
print x,y,z
#Is this right?
if x < y:
    if x < z: print 'x is least'
    else: print 'z is least'
else: print 'y is least'


The problem with this code is that it doesn't consider different situations. This example compares x and y, and x and z, but it does not compare y and z.

So for example, if we say x = 15, y = 13, z = 11.
The code will look and say, okay, x is not less than y. It'll skip down to the else statement, and print 'y is least'.
In actuality, z is least, but the program never compares y and z.

(Reposted to fix a small mistake.)
jetamors: Yoruichi is really hot (Default)

[personal profile] jetamors 2010-01-11 12:10 am (UTC)(link)
That's correct. This isn't a bug in the sense that the program won't run. The problem is that the code doesn't do what we want it to do: return the smallest number under every possible condition.

Consider a case where our intent is different: let's say we decide that if x is not less than y, then we don't care what z is. In that case, this code would be perfectly fine.
dodificus: (Default)

[personal profile] dodificus 2010-01-13 03:48 am (UTC)(link)
In the conditional statements readings there are some exercises. Do you know if they've got the solutions somewhere?

[personal profile] aranthe 2010-01-13 09:56 pm (UTC)(link)
If you don't find the solutions, I can post mine. I've tested them to be sure they work.

[personal profile] aranthe 2010-01-14 11:19 pm (UTC)(link)

Okay. I'll annotate them and try to get them posted sometime tomorrow (Friday).

ionabdRgPETKlanJ

(Anonymous) 2012-01-06 05:02 pm (UTC)(link)
I hate my life but at least this makes it baearble.

[personal profile] aranthe 2010-01-14 11:21 pm (UTC)(link)

Oops—forgot to ask: Do I put them under this thread or start another?

McPLHfDdvRaKImSAU

(Anonymous) 2012-01-06 05:22 pm (UTC)(link)
You've impressed us all with that postnig!

gZFJGTwPZPOEkpw

(Anonymous) 2012-01-07 06:16 am (UTC)(link)
Enlightening the world, one helpful arctile at a time.