Here is a quick outline of what will be covered on Midterm #1. We will be going over this in detail during class this week as well.

In addition, here are a few sample problems that you can try. (We may be going over some of these in detail during class if you wish).

Evaluate the following expressions and note the data type of the result (solutions will be posted below later)

Program #3: Trace the output of each loop (the "-----" divider denotes a new program):

count = 0 while count < 10: print ('Hello') count += 1 ———— x = 10 y = 0 while x > y: print (x, y) x = x - 1 y = y + 1 ———— keepgoing = True x = 100 while keepgoing: print (x) x = x - 10 if x < 50: keepgoing = False ———— x = 0 while True: x += 1 print (x) if x ** 2 > 36: break elif x % 2 == 0: continue print ("looping!")

a = 5 b = 6 c = 20 d = 24 if a < b and b * 2 < c: print ("Python Case 1") print ("A", '\t', "B", '\t', "C") if a * 2 == c: print (a*2, '\t', a*2, '\t', a*2) elif a * 3 == c: print (a*3, '\t', a*3, '\t', a*3) elif a * 4 == c: print (a*4, '\t', a*4, '\t', a*4) else: print ('?', '\t', '?', '\t', '?') else: print ("Python Case 2") print ("a", '\t', "b", '\t', "c") if b * 2 == d: print (b*2, '\t', b*2, '\t', b*2) elif b * 3 == d: print (b*3, '\t', b*3, '\t', b*3) elif b * 4 == d: print (b*4, '\t', b*4, '\t', b*4) else: print ('?', '\t', '?', '\t', '?')

Credit card qualifier How much do you make per year? 30000 Do you own your home? (y/n) y You qualify! Credit card qualifier How much do you make per year? 35000 Do you own your home? (y/n) n How much do you pay in rent per month? 1000 You qualify! Credit card qualifier How much do you make per year? 50000 Do you own your home? (y/n) n How much do you pay in rent per month? 5000 Sorry, you don't qualify. Your rent is too high

rate = str(input("How much do you make per hour? ‘)) hours = input("How many hours did you work this week? ") if hours < 40: pay = rate * hours if hours > 40 pay = rate * 40 ot_pay = (hours-40) ** (rate*1.5) print ("Your total pay is, pay + ot_pay")

How much money do you have?: 10.00 What would you like to buy? Donut (d) – 1.50 Coffee (c) – 1.00 Bagel (b) – 2.50 Scone (s) – 2.75 Enter your choice (d/c/b/s): d You can purchase 6 donuts with $ 10.0

Student name: Craig Combined SAT Score: 1800 High school GPA: 3.2 # of extracurricular activities: 3 Craig should be admitted! Another student? yes Student name: John Combined SAT Score: 1500 High school GPA: 3.1 # of extracurricular activities: 7 John should be admitted! Another student? yes Student name: Chris Combined SAT Score: 1300 High school GPA: 2.9 # of extracurricular activities: 8 Chris should not be admitted. Another student? no

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Evaluation Problems

*Expression*	*Evaluates To*	*Data Type*
5 – 2	3	integer
5 ** 2	25	integer
‘5’ + ‘2’	52	string
‘5’ * 2	55	string
5 / 2	2.5	float
5 // 2	2	integer
5 % 2	1	integer
5 + 2.0	7.0	float
5.0 * 2.0	10.0	float
10 > 2	True	Boolean
2 < 1	False	Boolean
2 != 4	True	Boolean
4 == 2**2	True	Boolean
‘cat’ < ‘dog’	True	Boolean
‘Cat’ < ‘dog’	True	Boolean
5 > 2 and 10 > 11	False	Boolean
5 > 2 or 10 > 11	True	Boolean
5 > 2 and not (10 > 11)	True	Boolean
str.lower(‘HeLLo’)	hello	string
str.upper(‘HeLLo’)	HELLO	string
format(5.1, ‘.2f’)	5.10	string
format(5.1, ‘>10.2f’)	" 5.10"	string
random.randint(1,5)	3	integer
len(‘cat’)	3	integer
len(‘cat’ + ‘dog’)	6	integer
not (5>2 and 5 < 4)	True	Boolean

Short Answers

Explain what a Boolean expression is and why you would use one while programming. Give three examples.

A Boolean expression is an expression that compares two or more values. It almost always involves the use a relational operator (>, <, ==, !=, etc) and always evaluates to True or False. We use Boolean expressions in Python to ask a question (i.e. if number < 0 then print "no negative numbers allowed!"), to control a repetition structure (i.e. while keepgoing == True, perform some operation) and to store a logical value in a variable (i.e. answer = 5 > 2)

Identify three functions that convert data from one data type to another. Provide a practical example of each function and describe when you would use it in an actual program.

The float(), int() and str() functions convert data from one data type to another. Here are a few examples:

# turn the user's input into a floating point number
answer = float(input("Enter a number: "))

# turn a String into an integer
a = "525"
b = int(a)

# convert a number into a String
a = 525
b = str(a)

Explain the differences and simliarities between the "if" statement and a "while" statement in Python

Both an "if" statement and a "while" statement utilize Boolean expressions. In the case of an "if" statement, if the attached Boolean expression evaluates to True then the body of the "if" statement will execute one time. In the case of a "while" statement, if the attached Boolean experession evalutes to True then the body of the "while" statement will execute, and then the condition will be re-evaluated at the end of the statement to see if it is still True - if so the body of the "while" statement will be executed again.

Name and describe three different data types in Python and when they could be used in a program

Integer: used to store whole number values. Useful for creating "counter" accumulator variables. Float: used to store floating point numbers. Useful for storing currency values. String: used to store sequences of characters, such as "Hello, World!"

Imagine you have the following while loop. Describe two different ways to stop this loop from iterating.

keepgoing = "yes"
while keepgoing == "yes":
	# statements go here

You could call the "break" statement from within the loop or you could flip the value of "keepgoing" to something other than "yes"

Trace The Output

(just copy and paste the code into IDLE to see the output!)

Programming Problems

Problem #1

word1 = input("Word 1: ")
word2 = input("Word 2: ")

if word1 > word2:
    print (word2, word1)

else:
    print (word1, word2)

Problem #2

word1 = input("Word 1: ")
word2 = input("Word 2: ")



if len(word1) > len(word2):
    print (word2, word1)

else:
    print (word1, word2)

Problem #3:

import random

die1 = random.randint(1,6)
die2 = random.randint(1,6)

print ("Virtual dice roll:", die1, "and", die2)

Problem #4

import random

usernum = int(input("Enter an integer (1-6): "))
compnum = random.randint(1,6)

if usernum == compnum:
    print ("you win!")

else:
    print ("try again!")

Problem #5

print ("Credit card qualifier")
salary = int(input("How much do you make per year? "))
own = input("Do you own your home? (y/n) ")

if own == 'y':
    if salary >= 30000:
        print ("You qualify!")
    else:
        print ("You don't qualify.  You need to make at least 30,000 per year and own your home.")

else:
    if salary < 30000:
        print ("You don't qualify.  You need to make at least 30,000 per year and own your home.")
    else:        
        rent = int(input("How much do you pay in rent per month? "))

        if rent > 0.05 * salary:
            print ("Sorry, you don't qualify.  Your rent is too high")
        else:
            print ("You qualify!")

Problem #6

test1 = float(input("Test 1: "))
test2 = float(input("Test 2: "))
test3 = float(input("Test 3: "))
homework = float(input("Homework: "))

test_avg = (test1 + test2 + test3) / 3
class_avg = (test_avg + homework) / 2

print ("Class average:", format(class_avg, '.2f'))
print ("Letter Grade: ", end='')

if class_avg > 90:
    print ("A")

elif class_avg > 80:
    print ("B")

elif class_avg > 70:
    print ("C")

elif class_avg > 65:
    print ("D")

else:
    print ("F")

Problem #7

# get sales
sales = float(input("Sales: "))

# calc profit
profit = 0.23 * sales

# output
print ("Projected profit:", profit)

Problem #8

# get square feet
square_feet = int(input("Square feet: "))

# convert to acres
acres = square_feet / 43560

# output
print ("In acres:", acres)

Problem #9

# get 5 prices
p1 = float(input("Price 1: "))
p2 = float(input("Price 2: "))
p3 = float(input("Price 3: "))
p4 = float(input("Price 4: "))
p5 = float(input("Price 5: "))

# calc subtotal
subtotal = p1+p2+p3+p4+p5

# calc tax
tax = 0.06 * subtotal

# output
print ("Subtotal:", subtotal)
print ("Tax:", tax)
print ("Total:", subtotal+tax)

Problem #10

# get 2 digit integer
num = int(input("Number: "))

# extract tens and ones
tens = num // 10
ones = num % 10

# construct the reversed number
rev = ones*10 + tens*1

# output
print (num, "reversed is:", rev)

print (num, "+", rev, "is", num+rev)

Problem #11

counter = 1
while counter <= 100:
    print (counter, " ", end="")
    counter += 1

Problem #11 Extension #1

counter = 1
while counter <= 100:
    if counter % 2 == 0:
        print (counter, " ", end="")
    counter += 1

Problem #11 Extension #3

while True:
    choice = input("Enter \"even\" or \"odd\": ")

    if choice == "even" or choice == "odd":
        break
    else:
        print ("Sorry, that's not a valid choice!")


if choice == "even":
    counter = 2

    while counter <= 100:
        print (counter, " ", end="")
        counter += 2

if choice == "odd":
    counter = 1

    while counter <= 100:
        print (counter, " ", end="")
        counter += 2

Problem #12

total = 0

keepgoing = "yes"
while keepgoing == "yes":
    price = float(input("Enter a price value: "))
    total += price
    keepgoing = input("Go again? ")

print ("Total is", total)

Problem #13

secret = 5

while True:
    guess = int(input("Guess a number between 1 and 10: "))

    if guess == secret:
        print ("Congrats!")
        break
    elif guess < secret:
        print ("Too low")
    else:
        print ("Too high")

Problem #14

import random

while True:
    numdigits = int(input("Enter a number of digits, positive numbers only: "))
    if numdigits < 1:
        print ("Try again!")
    else:
        break

counter = 1
while counter <= numdigits:
    print (random.randint(1, 100), " ", end="")
    counter += 1

Problem #15

print (format("Number", "<10s"), format("Number*2", "<10s"))

counter = 0
while counter < 10:
    print (format(counter, "<10d"), format(counter*2, "<10d"))
    counter += 1

Problem #16

rate = float(input("How much do you make per hour? "))
hours = float(input("How many hours did you work this week? "))

if hours < 40:
    pay = rate * hours
else:
    ot_pay = (hours-40) * (rate*1.5)
    pay = rate * 40 + ot_pay

print ("Your total pay is", pay)

Problem #17

# get money from the user
money = float(input("How much money do you have?: "))

print ("What would you like to buy?")
print ("Donut  (d) – 1.50")
print ("Coffee (c) – 1.00")
print ("Bagel  (b) – 2.50")
print ("Scone  (s) – 2.75")

# get user choice
choice = input("Enter your choice (d/c/b/s): ")

# evaluate choice
if choice == 'd':

    # note -- the // operator performs integer division and generates the
    # integer result of a division operation.  HOWEVER, both money and the value
    # 1.5 are floats!  Remember what happens when you have a math expression with
    # floating point numbers.  the integer division operator will generate an integer,
    # but Python will cast the result as a float (essentially adding .0 to the integer)
    # casting the result as an int using the int() function fixes this
    print ("You can purchase", int(money//1.5), "donuts with", money)

elif choice == 'c':
    print ("You can purchase", int(money//1.0), "cups of coffee with", money)
elif choice == 'b':
    print ("You can purchase", int(money//1.0), "bagels with", money)
elif choice == 's':
    print ("You can purchase", int(money//1.0), "scones with", money)
else:
    print ("Sorry, we don't sell that!")

Problem #18

# get two numbers
n1 = float(input("Number: "))
n2 = float(input("number: "))

# get an operation code, making sure to validate the data
# (keep the user "caught" until they supply a good value)
while True:
    op = input("Operation code (a/s/m/d): ")
    if op == 'a' or op == 's' or op == 'm' or op == 'd':
        break
    else:
        print ("Bad, try again")

# evaluate operation
if op == 'a':
    print (n1, "+", n2, "=", n1+n2)
elif op == 's':
    print (n1, "-", n2, "=", n1-n2)
elif op == 'm':
    print (n1, "*", n2, "=", n1*n2)
elif op == 'd':

    # make sure we don't crash if denom is 0
    if n2 == 0:
        print (n1, "/", n2, "=", "undefined")
    else:
        print (n1, "/", n2, "=", n1/n2)

Problem #19

# continually ask the user for input
while True:

    # get info
    name = input("Student name: ")
    sat  = float(input("SAT score: "))
    gpa  = float(input("GPA: "))
    act  = float(input("# of activities: "))

    # evaluate - normal admission
    if sat >= 1600 and gpa >= 3.0 and act >= 3:
        print (name, "should be admitted")
    elif act >= 5 and sat >= 1400 and gpa >= 2.8:
        print (name, "should be admitted")
    else:
        print (name, "should not be admitted")

    # keep going?
    again = input("Enter another student? ")
    if again == "no":
        break