Lecture 2

[winterthunder]

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?

Comments

[zulu]

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

[jetamors]

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.)

[dodificus]

In the conditional statements readings there are some exercises. Do you know if they've got the solutions somewhere?