CSE 1310 - Exams - Midterm 3 Practice Questions

Problem 1

What does this program print?

for i in range(1, 5):
    for j in range(i):
        print(i)  

Problem 2

Assume there is a file called file1.txt that contains the following lines. There is not a newline character at the end of the last line.

old pond...
a frog leaps in
water's sound

Given the above file contents, what does file file2.txt contain after running this code?

f = open('file1.txt', 'r')
x = f.readlines()
x.reverse()
f.close()

f = open('file2.txt', 'w')
for i in x:
    i = i.strip()
    print(i, file=f)
f.close()

Problem 3

What does this program print?

def foo(s):
    if not type(s) is str:
        return None
    result = ''
    for i in range(0, len(s), 2):
        result = result + s[i]
    for j in range(1, len(s), 2):
        result = result + s[j]
    return result

## Main ##
def main():
    print(foo(5))
    print(foo('hweolrllod '))

main()

Problem 4

What does this program print?

def foo(L):
    result = []
    for i in L:
        s = ''
        for j in range(0, len(i)):
            if j % 2 == 0:
                s = s + i[j].upper()
            else:
                s = s + i[j]
        result.append(s)
    return result

## Main ##
def main():
    x = ['spam', 'eggs', 'bacon']
    print(foo(x))

main()

Problem 5

Write a function mirror(file1, file2), that takes two strings as arguments (two file names) and reads the lines in file1, reverses the the order of the characters in each line and writes the result to file2. For example if the contents of file1 are:

hello
world

then the function should write file2 as:

olleh
dlrow

You can see it is a mirror image. Be careful of newline charaters. You can remove them and add your own back where needed:

line_from_file = line_from_file.strip()
...
line_to_write = line_to_write + '\n'

Problem 6

def foo(list1):
    if not bar(list1) == True:
        return None
    s = ""
    for item in list1:
        for x in item:
            s = s + str(x) + ' '
        s = s + '\n'
    return s

def main():
    L = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
    print(foo(L))

main()

The above program takes the given list, verifies it is an appropriately structured list, and converts it to a 2D string representation (so it looks like a matrix). The code is incomplete; the verification function bar(list1) has not been implemented. Write the function bar(list1) that foo(list1) can use to verify that its argument list1 is in the expected format:

• If list1 is a list of three sublists, each of which contains 3 integers, then bar(list1) returns True.
• Otherwise, bar(list1) returns False.

Problem 7

for i in range(5, 0, -2):
    dots = ''                   # This is an empty string
    end = int((5-i)/2)
    for j in range(0, end):
        dots = dots + '.'     
    print(dots + '0'*i)

for i in range(3, 6, 2):
    num_dots = int((5-i)/2)
    print('.'*num_dots + '0'*i)  

Problem 8

spam
eggs
bacon

fh = open('file.txt', 'r')
lines = fh.readlines()
fh.close()

for i in range(0, len(lines)):
    lines[i] = lines[i].strip() # Removes newline characters

# Get maximum line length
m = 0
for line in lines:
    l = len(line)
    if l > m:
        m = l

fh = open('file.txt', 'w')
for i in range(0, m):
    s = ''
    for line in lines:
        if i >= len(line):
            s = s + ' '
        else:
            s = s + line[i]
        s = s + ' '
    print(s, file=fh)
fh.close()

Problem 9

def main():
    d = {1 : "car",
         2 : "house",
         3 : "boat",
         4 : "dog",
         5 : "kitchen"} 
    L = list(d.keys()) 
    i = 0 
    while i < len(L):
        k = L[i]
        if k < 3 : 
            d[ d[k] ] = "zebra"
        i += 1
    for k in d :
        print(k, d[k]) 

main()

Problem 10

• The function takes two integers, start and end as arguments.
• If either argument is not an integer (i.e., not of type int), foo(start, end) returns None.
• If start > end, foo(start, end) returns None.
• Otherwise, the function uses nested for loops to create a list that contains all the possible pairs of an odd number and an even number using numbers from start up to and including end.

foo(1, 5)

[ [1, 2], [1, 4], [3, 2], [3, 4], [5, 2], [5, 4] ]

Problem 11

• Function foo takes two strings as arguments, s1, s2.
• If s1 or s2 is not a string (i.e., of type str), foo(s1, s2) returns None.
• If s1 and s2 do not have the same length, foo(s1, s2) returns None.
• Otherwise, foo(s1, s2) returns a string that is the result of interleaving the characters of the two strings.

• foo('hello', 'world') should return 'hweolrllod'. In this result, the 'h' was taken from s1, the 'w' from s2, the 'e' from s1, the 'o' from s2, and so on.
• foo('a1', 'b2) should return 'ab12'.

Problem 12

def foo(x, y):
    x = x.lower()
    y = y.lower()
    for i in x:
        for j in y:
            if i == j:
                return True
        return False

## Main ##
def main():
    a = ['Hello', 'World']
    b = ['Spam', 'eggs', 'hello']
    print(foo(a, b))

main()

Problem 13

For example:

• print(foo([1,2,3],[ 'one', 'two', 'three'])) prints {1: 'one', 2:'two', 3:'three'}
• foo(['a', 'b, c'],[30, 20, 25]) prints {'a':30, 'b':20, 'c':25}
• foo(['a', 'b, c'],[30, 20]) prints None

Problem 14

• foo({'a':30, 'b':20, 'c':25}) will print: b c a, since b has the lowest value (20), followed by c with value 25, and by a with value 30.