# Sample Final

1. Evaluate each expression. Indicate floats by including a decimal point (so to show 1 as a float, write “1.0”) If any cannot be evaluated, say why.
1. 3 + 5.0
2. 10 % 4 + 7 / 2
3. abs(5 - 20 / 3) ** 4
4. range(4, 13, 3)
5. "If %d + %d = %2.2f, then %s" % (2, 2, 4, "bye!")
6. 4 / "3"
1. 8.0
2. 5
3. 1
4. [4, 7, 10]
5. "If 2 + 2 = 4.00, then bye!"
6. A string cannot divide an integer, so this produces a TypeError
2. Convert the following into Python:
1. The volume vol of a sphere is 4πr 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
1. include math
vol = 4.0 * math.pi * r / 3.0
2. include string
string.replace('e', '3')
3. 3 * 27 - 159
3. 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.
if score < 1:
print "F"
elif score < 2:
print "D"
elif score < 3:
print "C"
elif score < 4:
print "B"
else:
print "A"
4. 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 float(a) / n
Answer: This computes the (floating point) average of the positive numbers in the list lst.
5. Rewrite the function in problem 4 so that it uses a “for” loop, not a “while” loop.
def f(lst):
a = 0
for i in lst:
if i <= 0:
continue
a += i
return float(a) / len(lst)
6. What does the following program do:
d = dict()
while True:
try:
line = raw_input("EOF to stop> ")
except EOFError:
break
for i in line:
d[i] = d.get(i, 0) + 1
u = d.keys()
for i in u:
print i, d[i]
Answer: This prints a list of characters in the input (excluding the newlines and/or carriage return), and the number of times each character appears in the input.
7. 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)
Answer: The function prints the digits in the number n. So, this prints
174