  Spring Semester 2007

Lab One Help (Part Two): Answers to some of the questions.
Problem 14 in the list of questions; we can start as sketched below.

```num = raw_input("Enter the points: ")
num = float(num)

if (num >= 3.85):
print "A"
elif (num >= 3.5):
print "A-"
else:
print "The rest is for you to complete."```

Problem 15: the key is to import the random module and use the random.randrange(...) method.

Problem 16: range(...) produces a list of integers.

Here's an example of a list; for 5 times we select elements from it at random.

```import random
a = range(10)
print a
for i in range(5):
j = random.randrange(len(a))
print a[j]```

Interestingly enough this works for strings too:

```import random
a = "johnny english"
print a
for i in range(5):
j = random.randrange(len(a))
print a[j]```

Problem 18: the i-th multiple of 3 is 3 times i.

Problem 19: using an index, just as in the examples above (same for lists).

Problem 20: extremely simple, requires minor modifications to the "johnny english" example above.

Problem 21: print a[len(a)-1] + a[1:len(a)-1] + a.

This would be a perfect time to discuss negative indexing: a[-1] + a[1:-1] + a works just as well.

Problem 22: there are two approaches to this problem, at least.

One simply uses the loop backwards from len(a)-1 to 0, one step at a time, and prints individual characters.

The other one reverses the string in the same manner by creating a new string, then printing that string.

Problem 23: a[1:]+a is produced and stored in a at each iteration.

Problem 24: this the first circumstance where a while loop is needed.

```bal = 10000
rat = 0.005
mon = 0

while bal >= 500 :
mon += 1
bal = bal + rat * bal
bal -= 500
print mon, bal

print "This money will last", mon / 12, "year and", mon % 12, "months."
```

Problem 25: is for you to work out.

Problem 26: how much of this problem is solved by the following code?

```import random

secret = random.randrange(100)

count = 0

guess = raw_input(str(count) + ". Enter your guess: ")

while guess != str(secret):
if guess == "show":
print "I have chosen", secret
else:
count += 1
guess = raw_input(str(count) + ". Enter your guess: ")
```

Updated by Adrian German for A202/A598