CS 151, fall 2019
Exam 2

Points - the amount/problem is listed for each problem.  There are a total of 39.5 points total

Please fill in the following.

0) Name:



1) Python keywords (8 points, 1/2 point each)
For this section answer with the appropriate python keyword

1.1) Function to generate a sequence of numbers:
range

1.2) Boolean values (two keywords):
True, False

1.3) Loop with only condition:
while

1.4) Conditional statements (three keywords):
if, elif, else

1.5) Handle an exception (2 keywords):
try, except

1.6) Text data type:
string

1.7) Determine whether two objects are the same object(not just value):
is

1.8) Declare a function:
def

1.9) Boolean operator, negates: 
not

1.10) To load a module:
import

1.11) Function to write to the screen:
print

1.12) Data type for True and False:
Boolean

1.13) Boolean operator, True if either side is True:
or

1.14) Exit the current loop:
break

1.15) Test if something is inside of a list/string/tuple/dictionary:
in

1.16) Special value for a variable that has no value: 
None



2) Evaluate the Python expression (8 points, 1/2 point each)
Assume the following initialization code has just run.  Write exactly what Python would print as the result of each expression.
line = "Hello, my name is HAL."
L = line.split(" ")
color = "blue"
pi = 3.14
prime = 9
d = {"num": pi, "list": L, "tuple": (1, 2, 3, 4)}

def total(var):
  t = 0
  for x in var: 
    t = t + x
  return x

def cat(var):
  s = ""
  for x in var:
    s = s + str(x)
  return s


2.1) 2 < 7
True

2.2) cat("hello")
'hello'

2.3) str(7) + str(6)
'76'

2.4) "7" == 7
False

2.5) len([1, 2, 4, 5])
4

2.6) L[3]
'is'

2.7) 7 <= 7
True

2.8) pi == 3.1
False

2.9) len(L)
5

2.10) 4 + 2 * 3
10

2.11) len("python")
6

2.12) True and False
False

2.13) d["tuple"][1]
2

2.14) len(color)
4

2.15) prime == "prime"
False

2.16) "0" in d["tuple"]
False




3) Short Python (7.5 points, 1.5 points each)
Assume the initialization code from problem 2 has just been run.  For each of the following, give the python code to complete the task.

3.1) print each letter in line variable on a separate line: 

for x in line:
  print(x)

# or
[print(x) for x in line]


3.2) multiply prime and pi variables, save into variable named c: 

c = prime * pi


3.3) print first 3 characters in color variable: 

print(color[:3])

# or
for i in range(0, 3):
  print(color[i])


3.4) print keys and values in d variable: 

print(d.keys(), d.values())

# or
for k, v in d.items():
  print(k, v)

# or
for k in d:
  print(k, d[k])


3.5) print last item in L variable: 

print(L[-1])

# or
print(L[len(L)-1])


4) Python functions (8 points, 4 points each)
Create a python function to do each of the following.  
4.1) Parameter is a filename - open, read and print the file

def funName(x):
  f = open(x)
  s = f.read()
  f.close()
  print(s)


4.2) Parameter is a dictionary, changes all values to be None (leave keys as they are)

def fun2(d):
  for k in d:
    d[k] = None


5) Play computer (8 points, 4 points each)
5.1) Selection Sort
def selection_sort(arr):

    for i in range(len(arr)):
        # index of the minimum value
        minx = i

        for j in range(i+1, len(arr)):
            if arr[j] < arr[minx]:
                minx = j

        # Swap values
        tmp = arr[minx]
        arr[minx] = arr[i]
        arr[i] = tmp
L = [5, 9, 3, 2, 4]
selection_sort(L)

For each value of i, write what L is at the end of the loop inside selection_sort

i=0
2, 9, 3, 5, 4

i=1
2, 3, 9, 5, 4

i=2
2, 3, 4, 5, 9

i=3
2, 3, 4, 5, 9

i=4
2, 3, 4, 5, 9


5.2) Play Computer

def recurse(i):
    if i < 10:
        print(i)
        recurse(i+2)
    else:
        print('Done')
recurse(1)

Write what is i each time it changes, and everything that is output to the screen.

i: 1, 3, 5, 7, 9, 11

screen: 
1
3
5
7
9
Done