Sample Final

The actual one will be longer, but these are the types of questions likely to be on it.

1. Multiple choice: which of the following expressions will cause an error to occur when it is evaluated?
   1. 3 + 5.0
   2. 10 % 4 + 7 // 2
   3. abs(5 - 20 // 3) ** 4
   4. "If %d + %d = %2.2f, then %s" % (2, 2, 4, "bye")
   5. 4 // "3"

2. Multiple choice: if s = "abcdefg", what is the value of s[2:-4]?
   1. "bc"
   2. "c"
   3. "" (that is, the empty string)
   4. "fed"
   5. It causes an exception

3. Convert the following into Python; you may assume the string and math modules are imported already:
   1. The volume vol of a sphere is 4πr³ divided by 3 (remember the result is a floating point number!)
   2. The value of the string variable str with all occurrences of the letter “e” replaced by the character “3”
   3. Subtract 159 from the product of 3 and 27, using integers

4. The A–F grading system assigns the following grades to scores. If your score is less than 1 point, you get an F; if it is less than 2 points, you get a D; if it is less than 3 points, you get a C; if you get less than 4 points, you get a B; and if you get 4 points or more, you get an A. Write an “if” statement that, given a score in the variable score, prints the corresponding grade.

5. What does the following function do when given a list of numbers as the argument?

   def f(lst):
   	a = i = 0
   	n = len(lst)
   	while i < n:
   		if lst[i] <= 0:
   			i += 1
   			continue
   		a += lst[i]
   		i += 1
   	return a / n
   

6. Rewrite the function in the previous problem so that it uses a “for” loop, not a “while” loop.

7. What does the following program do:

   d = dict()
   while True:
       try:
           line = input("EOF to stop> ")
       except EOFError:
           break
       for i in line:
           d[i] = d.get(i, 0) + 1
   u = d.keys()
   for i in sorted(u):
       print(i, d[i])
   

8. What does the following program do:

   def y(n):
       if n < 10:
           return str(n)
       else:
           d = str(n % 10)
           return y(n // 10) + d
   
   print(y(174))
   

9. When given a non-empty list lst of integers, the following function is supposed to return the largest element of the list. But it does not work. Please state what is missing and fix the program:

   def largest(lst):
       x = largest(lst[1:])
       if x < lst[0]:
           return lst[0]
       else:
           return x