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Chapter 5 – Functions
Up until this point, we have viewed a computer program as a single series of instructions. Most
programs, however, consist of distinct groups of instructions, each of which accomplishes a
specific task. Such a group of instructions is referred to as a “routine.” Program routines, called
“functions” in Python, are a fundamental building block in software development. We take our
first look at functions in this chapter.
OBJECTIVES
After reading this chapter and completing the exercises, you will be able to:









Explain the concept of a program routine
Explain the concept of parameter passing
Explain the concept of value-returning and non-value-returning functions
Explain the notion of the side-effects of a function call
Differentiate between local scope and global scope
Define and use functions in Python
Explain the concept of keyword and default arguments in Python
Write a Python program using programmer-defined functions
Effectively use trace statements for program testing
Chapter Overview
The purpose of this chapter is to introduce to students the fundamental notion of a program
routine (function). This includes function definition, value-returning vs. non-value-returning
functions, formal vs. actual arguments, variable scope (local vs. global variables), and the
particular Python features of default and keyword arguments.
Section 5.1 – Program Routines
Section 5.1.1 introduces a routine as a named group of instructions performing some task. A
routine is said to be invoked as many times as needed. Routines in Python are said to be called
functions. Section 5.1.2 descibes how functions are defined in Python. The terms formal
parameters (“parameters”) and actual arguments (“arguments”) are introduced. Also
described in this section is the difference between value-returning and non-value-returning
functions, with the mention of a side effect resulting from calls to non-value-returning
functions. Finally, calls to value-returning functions are described as expressions, and calls to
non-value-returning functions as statements.
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Copyright 2013 John Wiley and Sons
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Section 5.1.3 Let’s Apply It – “Temperature Conversion Program” (Function Version)
This Let’s Apply It section involves the use of both value-returning and non-value-returning
functions. The program converts temperatures from Fahrenheit to Celsius and Celsius to
Fahrenheit.
Section 5.2 – More on Functions
In this section, the details of parameter passing in general and in Python is covered.
Section 5.2.1 covers the use of value-returning functions, and how the various contexts in
which they can be called. An example of tuple assignment, a feature of Python, is mentioned.
Section 5.2.2 discusses the use of non-value-returning functions, and the context in which they
are called. It is also mentioned here that technically, all functions in Python are value-returning,
since when a function value is not explicitly returned by use of the return statement, the special
value None is returned.
Section 5.2.3 discusses parameter passing in more detail. It is here where mutable vs.
immutable arguments in Python are introduced. It is said that it is generally better to define
functions that do not return results through the arguments passed, and thus better to return
the results through a returned function value. Section 5.2.4 introduces the use of keyword
arguments in Python. Here is where the notion of positional arguments is first mentioned.
Section 5.2.5 discusses default arguments in Python. Finally, section 5.2.6 discusses variable
scope, including local variables (and local scope) and global variables (and global scope). The
concept of the lifetime of a variable is also mentioned. It is stated that the use of global
variables is generally considered to be bad programming style.
Section 5.1.3 Let’s Apply It – “GPA Calculation Program”
This Let’s Apply It section involves the use of both value-returning and non-value-returning
functions. The program converts temperatures from Fahrenheit to Celsius and Celsius to
Fahrenheit.
PROGRAM ERATTA
The GPA calculation program shown in Figure 5-14 in the text has an error. The
getGrades function is missing the last line: return semester_info. This code in
the provided source file is correct.
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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Section 5.3 COMPUTATIONAL PROBLEM SOLVING – Credit Card Calculation
Program
This Computational Problem Solving section demonstrates the development of a program that
determines the length of time needed to pay off a credit card account for a given balance,
interest rate, and monthly payment. It also determines the total interest paid.
Section 5.3.1 states the problem as displaying a table (as shown above) that shows the
decreasing balance and accumulating interest paid on a credit card account for a given credit
card balance, interest rate, and monthly payment. Section 5.3.2 discusses how the minimum
payment is typically calculated for a given credit card balance, with the option to make as
larger a payment as desired.
Section 5.3.3 lays out the program design (and the overall steps of the program). The program
requirements are given. The data description points out that only needing numerical values for
the loan amount, interest rate, and monthly payment made. The algorithm approach needed is
simply the calculation of the requirement minimal payment, which is a percentage of the
outstanding balance (2% or 3%), with a lower limit minimum payment (approximately $20).
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
3
Overall Program Steps
Section 5.3.4 demonstrates implementation and testing of the program. The program is
developed in three stages. Stage 1 develops the initial program, using a top down approach and
thus deferring the implementation of the functions called, displayWelcome and
displayPayments. These functions are initially implemented to contain only trace
statements, that indicated that the functions have been called, and the arguments called with
(for function displayPayments).
NOTE: There are no intentionally placed errors in the program development. This is the first
place in the text in which the notion of a trace statement is discussed.
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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SOLUTIONS TO CHAPTER EXERCISES
Section 5.1
1. Function avg returns the average of three values, as given in the chapter. Which of the following
statements, each making calls to function avg, are valid? (Assume that all variables are of numeric
type.)
(a)
(b)
(c)
(d)
(e)
result = avg(n1, n2)
result = avg(n1, n2, avg(n3, n4, n5))
result = avg(n1 + n2, n3 + n4, n5 + n6)
print(avg(n1, n2, n3))
result = avg(n1, n2, n3) + avg(n4, n5, n6)
ANSWER: (b), (c), (d), (e)
2. Which of the following statements, each involving calls to function displayWelcome displaying a
welcome message on the screen as given in the chapter, are valid?
(a)
(b)
(c)
(d)
print(displayWelcome)
displayWelcome
result = displayWelcome
displayWelcome()
ANSWER: (d)
Section 5.2
3. Suppose there are nine variables, each holding an integer value as shown below, for which the
average of the largest value in each line of variables is to be computed.
num1 = 10
num4 = 5
num7 = 20
num2 = 20
num5 = 15
num8 = 30
num3 = 25
num6 = 35
num9 = 25
max1 = 25
max2 = 35
max3 = 30
average = (max1 + max2 + max3) / 3.0
= (25 + 35 + 30) / 3.0
= 30.0
Using functions avg and max give an expression that computes the average as shown above using
only function calls, and no other operations.
ANSWER: avg(max([num1, num2, num3]), max([num4, num5, num6]), max([num7, num8,num9]))
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
5
4. Assume that there exists a Boolean function named isLeapYear that determines if a given year is
a leap year or not. Give an appropriate if statement that prints “Year is a Leap Year” if the year
passed is a leap year, and “Year is Not a Leap Year” otherwise, for a given variable whichYear.
ANSWER:
if isLeapYear(whichYear):
print('Year is a Leap Year')
else:
print('Year is Not a Leap Year')
5. For the following function definition and associated function calls,
def somefunction(n1, n2):
.
.
# main
num1 = 10
somefunction(num1, 15)
(a) list all the formal parameters
(b) list all the actual arguments
ANSWER:
(a) n1, n2
(b) num1, 15
6. For the following function, indicate whether each function call is proper or not. If improper, explain
why.
def gcd(n1, n2):
function gcd calculates the greatest common divisor of n1 and
n2, with the requirement that n1 be less than or equal to n2, and
n1 and n2 are integer values.
(a) a = 10
b = 20
result = gcd(a, b)
(b) a = 10.0
b = 20
result = gcd(a, b)
(c)
a = 20
b = 10
result = gcd(b ,a)
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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(d) a = 10
b = 20
c = 30
result = gcd(gcd(a, b), c)
(e) a = 10
b = 20
c = 30
print gcd(a, gcd(c, b))
ANSWERS:
(a)
(b)
(c)
(d)
(e)
VALID
INVALID. Only takes integer arguments.
VALID
VALID
INVALID. First argument must be less than or equal to second argument.
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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SOLUTIONS TO PYTHON PROGRAMMING EXERCISES
P1. Write a Python function named zeroCheck that is given three integers, and returns true if any of
the integers is 0, otherwise it returns false.
def zeroCheck(n1, n2, n3):
if n1 * n2 * n3 == 0:
return True
else:
return False
P2. Write a Python function named ordered3 that is passed three integers, and returns true if the
three integers are in order from smallest to largest, otherwise it returns false.
def ordered3(n1, n2, n3):
if n1 < n2 and n2 < n3:
return True
else:
return False
P3. Write a Python function named modCount that is given a positive integer, n, and a second positive
integer, m <= n, and returns how many numbers between 1 and n are evenly divisible by m.
def modCount(n, m):
count = 0
for k in range(2, n):
if k % m == 0:
count = count + 1
return count
P4. Write a Python function named helloWorld that displays "Hello World, my name is name ", for
any given name passed to the routine.
def helloWorld(name):
print('Hello world, my name is', name)
P5. Write a Python function named printAsterisks that is passed a positive integer value n, and
prints out a line of n asterisks. If n is greater than 75, then only 75 asterisks should be displayed.
def printAsterisks(n):
if n > 75:
n = 75;
for k in range(0, n + 1):
print('*', end='')
print()
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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P6. Write a Python function named getContinue that displays to the user “Do you want to continue
(y/n): ”, and continues to prompt the user until either uppercase or lowercase 'y' or 'n' is entered,
returning (lowercase) 'y' or 'n' as the function value.
def getContinue():
response = input('Do you want to continue (y:n): ')
while response not in ('y', 'n', 'Y', 'N'):
response = input('Do you want to continue (y:n): ')
if response in ('y', 'Y'):
return 'y'
else:
return 'n'
NOTE: This solution assumes that string methods upper/lower have not yet been covered
(introduced in Chapter 8 on Text Files).
P7. Implement a Python function that is passed a list of numeric values and a particular threshold
value, and returns the list with all values above the given threshold value set to 0. The list should be
altered as a side effect to the function call, and not by function return value.
def filterValues(lst, threshold_val):
for k in range(0, len(lst)):
if lst[k] > threshold_val:
lst[k] = 0
P8. Implement the Python function described in question P7 so that the altered list is returned as a
function value, rather than by side effect.
def filterValues(lst, threshold_val):
new_list = []
for k in range(0, len(lst)):
if lst[k] > threshold_val:
new_list.append(0)
else:
new_list.append(lst[k])
return new_list
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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SOLUTIONS TO PROGRAM MODIFICATION PROBLEMS
M1. Temperature Conversion Program: Adding Kelvin Scale
Modify the Temperature Conversion program in section 5.1.3 so that it allows the user to select
temperature conversion to include degrees Kelvin, in addition to degrees Fahrenheit and degrees
Celsius. Include input error checking for inappropriate temperature values. (NOTE: Refer to
questions M1 and M2 from Chapter 3.)
# Temperature Conversion Program (Figure 5-6)
# MODIFICATION: Allow conversion between Kelvin scale
def displayWelcome():
print('This program will convert a range of temperatures between')
print('Fahrenheit, Celsius and Kelvin\n')
def getScale():
which = input('Enter (F)ahrenheit, (C)elsius, or (Kelvin): ')
while which not in ('F', 'C', 'K'):
which = input('Enter (F)ahrenheit, (C)elsius, or (K)elvin: ')
return which
def displayConversion(from_scale, to_scale, start, end):
scales = ('F', 'C', 'K')
scale_names = ('Fahrenheit', 'Celsius', 'Kelvin')
print()
print(format('Degrees', '^12'), format('Degrees', '^12'))
print(format(scale_names[scales.index(from_scale)], '^12'),
format(scale_names[scales.index(to_scale)], '^12'))
for temp in range(start, end + 1):
if from_scale == 'F':
if to_scale == 'C':
converted_temp = (temp - 32) * 5/9
if to_scale == 'K':
converted_temp = ((temp - 32) * 5/9) + 273.15
elif from_scale == 'C':
if to_scale == 'F':
converted_temp = (9/5 * temp) + 32
elif to_scale == 'K':
converted_temp = temp + 273.15
elif from_scale == 'K':
if to_scale == 'F':
converted_temp = (9/5 * (temp - 273.13)) + 32
elif to_scale == 'C':
converted_temp = temp - 273.15
print(format(temp, '8.1f'), format(' ', '^3'),
format(converted_temp, '8.1f'))
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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# ---- main
# Display program welcome
displayWelcome()
# Get temperature scales to convert between
print('Enter temperature scale to convert from ...')
convert_from = getScale()
print('\nEnter temperature scale to convert to ...')
convert_to = getScale()
# Get range of temperatures to convert
valid_temp = False
while not valid_temp:
temp_start = int(input('\nEnter start of temperature range to convert: '))
if (convert_from == 'F' and temp_start >= -459) or \
(convert_from == 'C' and temp_start >= -273) or \
(convert_from == 'K' and temp_start >= 0):
valid_temp = True
else:
print('Temperature entered below absolute zero')
temp_end = int(input('Enter ending temperature to convert: '))
while temp_end < temp_start:
print('End temperature cannot be less than starting temperature')
temp_end = int(input('Enter ending temperature to convert: '))
# Display range of converted temperatures
displayConversion(convert_from, convert_to, temp_start, temp_end)
This program will convert a range of temperatures between
Fahrenheit, Celsius and Kelvin
Enter temperature scale to convert from ...
Enter (F)ahrenheit, (C)elsius, or (Kelvin): F
Enter temperature scale to convert to ...
Enter (F)ahrenheit, (C)elsius, or (K)elvin: C
Enter start of temperature range to convert: 75
Enter ending temperature to convert: 90
Degrees
Fahrenheit
75.0
76.0
77.0
78.0
79.0
80.0
81.0
82.0
83.0
84.0
85.0
86.0
87.0
88.0
89.0
90.0
Degrees
Celsius
23.9
24.4
25.0
25.6
26.1
26.7
27.2
27.8
28.3
28.9
29.4
30.0
30.6
31.1
31.7
32.2
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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This program will convert a range of temperatures between
Fahrenheit, Celsius and Kelvin
Enter temperature scale to convert from ...
Enter (F)ahrenheit, (C)elsius, or (Kelvin): F
Enter temperature scale to convert to ...
Enter (F)ahrenheit, (C)elsius, or (Kelvin): K
Enter start of temperature range to convert: 75
Enter ending temperature to convert: 90
Degrees
Fahrenheit
75.0
76.0
77.0
78.0
79.0
80.0
81.0
82.0
83.0
84.0
85.0
86.0
87.0
88.0
89.0
90.0
Degrees
Kelvin
297.0
297.6
298.1
298.7
299.3
299.8
300.4
300.9
301.5
302.0
302.6
303.1
303.7
304.3
304.8
305.4
This program will convert a range of temperatures between
Fahrenheit, Celsius and Kelvin
Enter temperature scale to convert from ...
Enter (F)ahrenheit, (C)elsius, or (Kelvin): K
Enter temperature scale to convert to ...
Enter (F)ahrenheit, (C)elsius, or (Kelvin): C
Enter start of temperature range to convert: -100
Temperature entered below absolute zero
Enter start of temperature range to convert: 0
Enter ending temperature to convert: 10
Degrees
Kelvin
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
Degrees
Celsius
-273.1
-272.1
-271.1
-270.1
-269.1
-268.1
-267.1
-266.1
-265.1
-264.1
-263.1
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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M2. GPA Calculation Program: Accommodating First-Semester Students
Modify the GPA Calculation Program of section 5.2.7 so that it asks the student if this is their first
semester of grades. If so, the program should only prompt the students for their current semester
grades, and not their cumulative gpa and total earned credits, and display their semester gpa and
cumulative gpa accordingly.
# Temperature GPA Calculation Program (Figure 5-13)
# MODIFICATION: Accommodating First-Semester Students
def convertGrade(grade):
if grade == 'F':
return 0
else:
return 4 - (ord(grade) - ord('A'))
def getGrades():
semester_info = []
more_grades = True
empty_str = ''
print("Enter current semester grades ('A','B','C','D','F')")
while more_grades:
course_grade = input('Enter grade (hit Enter when done): ')
while course_grade not in ('A','B','C','D','F',empty_str):
course_grade = input('Enter letter grade received: ')
if course_grade == empty_str:
more_grades = False
else:
num_credits = int(input('Enter number of credits: '))
semester_info.append([num_credits, course_grade])
return semester_info
def calculateGPA(sem_grades_info, cumulative_gpa_info):
sem_quality_pts = 0
sem_credits = 0
current_cumulative_gpa, total_credits = cumulative_gpa_info
for k in range(len(sem_grades_info)):
num_credits, letter_grade = sem_grades_info[k]
sem_quality_pts = sem_quality_pts + \
num_credits * convertGrade(letter_grade)
sem_credits = sem_credits + num_credits
sem_gpa = sem_quality_pts / sem_credits
new_cumulative_gpa = (current_cumulative_gpa * total_credits +\
sem_gpa * sem_credits) / (total_credits + sem_credits)
return (sem_gpa, new_cumulative_gpa)
Introduction to Computer Science Using Python – Dierbach
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# ---- main
# program greeting
print('This program calculates semester and cumulative GPAs\n')
# first semester student?
response = input('Is this your first semester (y/n)? ')
while response not in ('y', 'n', 'Y', 'N'):
response = input('Is this your first semester (y/n)? ')
first_semester = response in ('Y', 'y')
# get current semester grade info
print()
semester_grades = getGrades()
if first_semester:
cumulative_gpa_info = (0, 0)
else:
total_credits = int(input('\nEnter total number of earned credits: '))
cumulative_gpa = float(input('Enter your current cumulative GPA: '))
cumulative_gpa_info = (cumulative_gpa, total_credits)
# calculate semester gpa and new cumulative gpa
semester_gpa, cumulative_gpa = calculateGPA(semester_grades, \
cumulative_gpa_info)
# display semester gpa and new cumulative gpa
print('\nYour semester GPA is', format(semester_gpa, '.2f'))
print('Your new cumulative GPA is', format(cumulative_gpa, '.2f'))
This program calculates semester and cumulative GPAs
Is this your first semester (y/n)? y
Enter
Enter
Enter
Enter
Enter
Enter
Enter
Enter
Enter
Enter
current semester grades ('A','B','C','D','F')
grade (hit Enter when done): A
number of credits: 3
grade (hit Enter when done): B
number of credits: 3
grade (hit Enter when done): B
number of credits: 3
grade (hit Enter when done): A
number of credits: 3
grade (hit Enter when done):
Your semester GPA is 3.50
Your new cumulative GPA is 3.50
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
14
This program calculates semester and cumulative GPAs
Is this your first semester (y/n)? n
Enter
Enter
Enter
Enter
Enter
Enter
Enter
Enter
Enter
Enter
current semester grades ('A','B','C','D','F')
grade (hit Enter when done): A
number of credits: 3
grade (hit Enter when done): B
number of credits: 3
grade (hit Enter when done): B
number of credits: 3
grade (hit Enter when done): A
number of credits: 3
grade (hit Enter when done):
Enter total number of earned credits: 12
Enter your current cumulative GPA: 3.2
Your semester GPA is 3.50
Your new cumulative GPA is 3.35
M3. GPA Calculation Program: Allowing for Plus/Minus Grading
Modify the GPA Calculation Program of section 5.2.7 so that it is capable of calculating a GPA for
plus/minus letter grades: A, A-, B+, B, B-, and so forth.
# GPA Calculation Program (Figure 5-14)
# MODIFICATION: Allowing for Plus/Minus Grading
def convertGrade(grade):
adjustment = 0.33
# get base grade
if grade[0] == 'F':
value = 0
else:
value = 4 - (ord(grade[0]) - ord('A'))
# make adjustment for any +/if len(grade) == 2:
if grade[1] == '+':
value = value + adjustment
else:
value = value - adjustment
return value
def getGrades(valid_grades):
semester_info = []
more_grades = True
empty_str = ''
print("Enter current semester grades ('A','A-','B+', ...)")
while more_grades:
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
15
course_grade = input('Enter grade (hit Enter if done): ')
if course_grade == empty_str:
more_grades = False
elif len(course_grade) == 1 or len(course_grade) == 2 and \
course_grade in valid_grades:
num_credits = int(input('Enter number of credits: '))
print()
semester_info.append([num_credits, course_grade])
else:
print('Invalid Grade -- Reenter: ')
return semester_info
def calculateGPA(sem_grades_info, cumulative_gpa_info):
sem_quality_pts = 0
sem_credits = 0
current_cumulative_gpa, total_credits = cumulative_gpa_info
for k in range(len(sem_grades_info)):
num_credits, letter_grade = sem_grades_info[k]
sem_quality_pts = sem_quality_pts + \
num_credits * convertGrade(letter_grade)
sem_credits = sem_credits + num_credits
sem_gpa = sem_quality_pts / sem_credits
new_cumulative_gpa = (current_cumulative_gpa * total_credits +\
sem_gpa * sem_credits) / (total_credits + sem_credits)
return (sem_gpa, new_cumulative_gpa)
# ---- main
# init
valid_grades = ('A','A-','B+','B','B-','C+','C','C-','D+','D','D-','F')
# program greeting
print('This program calculates semester and cumulative GPAs\n')
# get current GPA info
total_credits = int(input('Enter total number of earned credits: '))
cumulative_gpa = float(input('Enter your current cumulative GPA: '))
cumulative_gpa_info = (cumulative_gpa, total_credits)
# get current semester grade info
print()
semester_grades = getGrades(valid_grades)
# calculate semester gpa and new cumulative gpa
semester_gpa, cumulative_gpa = calculateGPA(semester_grades, \
cumulative_gpa_info)
# display semester gpa and new cumulative gpa
print('\nYour semester GPA is', format(semester_gpa, '.2f'))
print('Your new cumulative GPA is', format(cumulative_gpa, '.2f'))
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Copyright 2013 John Wiley and Sons
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This program calculates semester and cumulative GPAs
Enter total number of earned credits: 30
Enter your current cumulative GPA: 3.4
Enter current semester grades ('A','A-','B+', ...)
Enter grade (hit Enter if done): AEnter number of credits: 3
Enter grade (hit Enter if done): B++
Invalid Grade -- Reenter:
Enter grade (hit Enter if done): B+
Enter number of credits: 3
Enter grade (hit Enter if done): BEnter number of credits: 4
Enter grade (hit Enter if done): A
Enter number of credits: 3
Enter grade (hit Enter if done): C+
Enter number of credits: 2
Enter grade (hit Enter if done):
Your semester GPA is 3.22
Your new cumulative GPA is 3.34
M4. Credit Card Calculation Program: Summarized Output
Modify the Credit Card Calculation Program in section 5.3.3 so that the user is given the option of
either displaying the balance and interest paid month-by-month as currently written, or to simply
have the total number of months and the total interest paid without the month-by-month detail.
# Credit Card Calculation Program (Section 5.3)
# MODIFICATION: Summarized Output
def displayWelcome():
print('This program will determine the time to pay off a credit')
print('card and the interest paid based on the current balance,')
print('the interest rate, and the monthly payments made.')
def displayPayments(balance, int_rate, monthly_payment):
# init
num_months = 0
total_int_paid = 0
num_payments = 1
empty_year_field = format(' ', '8')
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# display heading
print('\n', format('PAYOFF SCHEDULE','>20'))
print(format('Year','>10') + format('Balance','>10') +
format('Payment Num', '>14') + format('Interest Paid','>16'))
# display year-by-year account status
while balance > 0:
monthly_int = balance * int_rate
total_int_paid = total_int_paid + monthly_int
balance = balance + monthly_int - monthly_payment
if balance < 0:
balance = 0
if num_months % 12 == 0:
year_field = format(num_months // 12 + 1, '>8')
else:
year_field = empty_year_field
print(year_field + format(balance, '>12,.2f') +
format(num_payments, '>9') +
format(total_int_paid, '>17,.2f'))
num_payments = num_payments + 1
num_months = num_months + 1
def displayBottomLine(balance, int_rate, monthly_payment):
# init
num_months = 0
total_int_paid = 0
num_payments = 0
# calculate number of payments and total interest paid
while balance > 0:
monthly_int = balance * int_rate
total_int_paid = total_int_paid + monthly_int
balance = balance + monthly_int - monthly_payment
num_payments = num_payments + 1
# display heading
print('\nTOTAL NUMBER OF PAYMENTS:', num_payments, format(' ', '4<'),
'TOTAL INTEREST PAID: ', format(total_int_paid, ',.2f'))
# ---- main
# display welcome screen
displayWelcome()
# get current balance and APR
balance = int(input('\nEnter the balance on your credit card: '))
apr = int(input('Enter the interest rate (APR) on the card: '))
monthly_int_rate = apr/1200
yes_response = ('y','Y')
no_response = ('n','N')
Introduction to Computer Science Using Python – Dierbach
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18
calc = True
while calc:
# calc minimum monthly payment
if balance < 1000:
min_monthly_payment = 20
else:
min_monthly_payment = balance * .02
# get monthly payment
print('\nAssuming a minimum payment of 2% of the balance ($20 min)')
print('Your minimum payment would be',
format(min_monthly_payment, '.2f'),'\n')
response = input('Use the minimum monthly payment? (y/n): ')
while response not in yes_response + no_response:
response = input('Use the minimum monthly payment? (y/n): ')
if response in yes_response:
monthly_payment = min_monthly_payment
else:
acceptable_payment = False
while not acceptable_payment:
monthly_payment = int(input('\nEnter monthly payment: '))
if monthly_payment < balance * .02:
print('Minimum payment of 2% of balance required ($' +
str(balance * .02) + ')')
elif monthly_payment < 20:
print('Minimum payment of $20 required')
else:
acceptable_payment = True
# check if single payment pays off balance
if monthly_payment >= balance:
print('* This payment amount would pay off your balance *')
else:
# display number of payments and interest paid
prompt = 'Do you wish to see the monthy payment details (y/n)? '
monthly_output = input(prompt)
while monthly_output not in ('Y','N','y','n'):
monthly_output = input(prompt)
if monthly_output in ('Y','y'):
displayPayments(balance, monthly_int_rate, monthly_payment)
else:
displayBottomLine(balance, monthly_int_rate, monthly_payment)
# calculate again with another monthly payment?
again = input('\nRecalculate with another payment? (y/n): ')
while again not in yes_response + no_response:
again = input('Recalculate with another payment? (y/n): ')
if again in yes_response:
calc = True
# continue program
print('\n\nFor your current balance of $' + str(balance))
else:
calc = False
# terminate program
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
19
This program will determine the time to pay off a credit
card and the interest paid based on the current balance,
the interest rate, and the monthly payments made.
Enter the balance on your credit card: 2500
Enter the interest rate (APR) on the card: 18
Assuming a minimum payment of 2% of the balance ($20 min)
Your minimum payment would be 50.00
Use the minimum monthly payment? (y/n): n
Enter monthly payment: 125
Do you wish to see the monthy payment details (y/n)? n
TOTAL NUMBER OF PAYMENTS: 24
TOTAL INTEREST PAID:
494.57
Recalculate with another payment? (y/n): y
For your current balance of $2500
Assuming a minimum payment of 2% of the balance ($20 min)
Your minimum payment would be 50.00
Use the minimum monthly payment? (y/n): n
Enter monthly payment: 250
Do you wish to see the monthy payment details (y/n)? y
PAYOFF SCHEDULE
Year
Balance
1
2,287.50
2,071.81
1,852.89
1,630.68
1,405.14
1,176.22
943.86
708.02
468.64
225.67
0.00
Payment Num
1
2
3
4
5
6
7
8
9
10
11
Interest Paid
37.50
71.81
102.89
130.68
155.14
176.22
193.86
208.02
218.64
225.67
229.06
Recalculate with another payment? (y/n): n
>>>
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
20
M5. Credit Card Calculation Program: Adjustable Minimum Payment
Modify the Credit Card Calculation program in section 5.3 so that the user can enter the percentage
from which the minimum monthly payment is calculated. Also modify the program so that this
minimum payment percentage is displayed along with the other credit card related information.
# Credit Card Calculation Program (Section 5.3)
# MODIFICATION: Adjustable Minimum Payment
def displayWelcome():
print('This program will determine the time to pay off a credit')
print('card and the interest paid based on the current balance,')
print('the interest rate, and the monthly payments made.')
def displayPayments(balance, int_rate, monthly_payment):
# init
num_months = 0
total_int_paid = 0
payment_num = 1
empty_year_field = format(' ', '8')
# display heading
print('\n', format('PAYOFF SCHEDULE','>20'))
print(format('Year','>10') + format('Balance','>10') +
format('Payment Num', '>14') + format('Interest Paid','>16'))
# display year-by-year account status
while balance > 0:
monthly_int = balance * int_rate
total_int_paid = total_int_paid + monthly_int
balance = balance + monthly_int - monthly_payment
if balance < 0:
balance = 0
if num_months % 12 == 0:
year_field = format(num_months // 12 + 1, '>8')
else:
year_field = empty_year_field
print(year_field + format(balance, '>12,.2f') +
format(payment_num, '>9') +
format(total_int_paid, '>17,.2f'))
payment_num = payment_num + 1
num_months = num_months + 1
# ---- main
# init
yes_response = ('y','Y')
no_response = ('n','N')
(moved here)
# display welcome screen
displayWelcome()
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
21
# get current balance and APR
balance = int(input('\nEnter the balance on your credit card: '))
apr = int(input('Enter the interest rate (APR) on the card: '))
monthly_int_rate = apr/1200
# get percentage for minimum monthly payment
percent_min = int(input('Enter percentage used to calculate min payment: '))
while percent_min < 1:
percent_min = input('Enter as integer value (e.g., 18): ')
# calc minimum monthly payment
min_monthly_payment = balance * (percent_min / 100)
if min_monthly_payment < 20:
min_monthly_payment = 20
# display payments and interest paid
calc = True
while calc:
# get monthly payment
print('\nAssuming a minimum payment of',str(percent_min) +
'% of the balance, \nyour minimum payment would be',
format(min_monthly_payment, '.2f'),'\n')
response = input('Use the minimum monthly payment? (y/n): ')
while response not in yes_response + no_response:
response = input('Use the minimum monthly payment? (y/n): ')
if response in yes_response:
monthly_payment = min_monthly_payment
else:
acceptable_payment = False
while not acceptable_payment:
monthly_payment = int(input('\nEnter monthly payment: '))
if monthly_payment < balance * (percent_min / 100):
print('Minimum payment of', str(percent_min) +
'% of the balance required ($' +
str(balance * (percent_min / 100)) + ')')
elif monthly_payment < 20:
print('Minimum payment of $20 required')
else:
acceptable_payment = True
# check if single payment pays off balance
if monthly_payment >= balance:
print('* This payment amount would pay off your balance *')
else:
# display month-by-month balance payoff
displayPayments(balance, monthly_int_rate, monthly_payment)
# calculate again with another monthly payment?
again = input('\nRecalculate with another payment? (y/n): ')
while again not in yes_response + no_response:
again = input('Recalculate with another payment? (y/n): ')
if again in yes_response:
calc = True
# continue program
print('\n\nFor your current balance of $' + str(balance))
else:
calc = False
# terminate program
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
22
This program will determine the time to pay off a credit
card and the interest paid based on the current balance,
the interest rate, and the monthly payments made.
Enter the balance on your credit card: 2500
Enter the interest rate (APR) on the card: 18
Enter percentage used to calculate min payment: 3
Assuming a minimum payment of 3% of the balance,
your minimum payment would be 75.00
Use the minimum monthly payment? (y/n): n
Enter monthly payment: 60
Minimum payment of 3% of balance required ($75.0)
Enter monthly payment: 100
PAYOFF SCHEDULE
Year
Balance
1
2,437.50
2,374.06
2,309.67
2,244.32
2,177.98
2,110.65
2,042.31
1,972.95
1,902.54
1,831.08
1,758.55
1,684.92
2
1,610.20
1,534.35
1,457.37
1,379.23
1,299.92
1,219.41
1,137.71
1,054.77
970.59
885.15
798.43
710.40
3
621.06
530.38
438.33
344.91
250.08
153.83
56.14
0.00
Payment Num
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Interest Paid
37.50
74.06
109.67
144.32
177.98
210.65
242.31
272.95
302.54
331.08
358.55
384.92
410.20
434.35
457.37
479.23
499.92
519.41
537.71
554.77
570.59
585.15
598.43
610.40
621.06
630.38
638.33
644.91
650.08
653.83
656.14
656.98
Recalculate with another payment? (y/n): n
>>>
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
23
M6. Credit Card Calculation Program: Recalculation with New Balance
Modify the Credit Card Calculation program in section 5.3 so that the program will allow the user to
recalculate a new payoff schedule for a new entered balance.
# Credit Card Calculation Program (Section 5.3)
# MODIFICATION: Recalculation with New Balance
def displayWelcome():
print('This program will determine the time to pay off a credit')
print('card and the interest paid based on the current balance,')
print('the interest rate, and the monthly payments made.')
def displayPayments(balance, int_rate, monthly_payment):
# init
num_months = 0
total_int_paid = 0
payment_num = 1
empty_year_field = format(' ', '8')
# display heading
print('\n', format('PAYOFF SCHEDULE','>20'))
print(format('Year','>10') + format('Balance','>10') +
format('Payment Num', '>14') + format('Interest Paid','>16'))
# display year-by-year account status
while balance > 0:
monthly_int = balance * int_rate
total_int_paid = total_int_paid + monthly_int
balance = balance + monthly_int - monthly_payment
if balance < 0:
balance = 0
if num_months % 12 == 0:
year_field = format(num_months // 12 + 1, '>8')
else:
year_field = empty_year_field
print(year_field + format(balance, '>12,.2f') +
format(payment_num, '>9') +
format(total_int_paid, '>17,.2f'))
payment_num = payment_num + 1
num_months = num_months + 1
# ---- main
# display welcome screen
displayWelcome()
# get current balance and APR
balance = int(input('\nEnter the balance on your credit card: '))
apr = int(input('Enter the interest rate (APR) on the card: '))
monthly_int_rate = apr/1200
yes_response = ('y','Y')
no_response = ('n','N')
calc = True
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
24
while calc:
# calc minimum monthly payment
if balance < 1000:
min_monthly_payment = 20
else:
min_monthly_payment = balance * .02
# get monthly payment
print('\nAssuming a minimum payment of 2% of the balance ($20 min)')
print('Your minimum payment would be',
format(min_monthly_payment, '.2f'),'\n')
response = input('Use the minimum monthly payment? (y/n): ')
while response not in yes_response + no_response:
response = input('Use the minimum monthly payment? (y/n): ')
if response in yes_response:
monthly_payment = min_monthly_payment
else:
acceptable_payment = False
while not acceptable_payment:
monthly_payment = int(input('\nEnter monthly payment: '))
if monthly_payment < balance * .02:
print('Minimum payment of 2% of balance required ($' +
str(balance * .02) + ')')
elif monthly_payment < 20:
print('Minimum payment of $20 required')
else:
acceptable_payment = True
# check if single payment pays off balance
if monthly_payment >= balance:
print('* This payment amount would pay off your balance *')
else:
# display month-by-month balance payoff
displayPayments(balance, monthly_int_rate, monthly_payment)
# calculate again?
response = input('\nDo you wish to do another calculation? (y/n): ')
while response not in yes_response + no_response:
response = input('Do you wish to do another calculation? (y/n): ')
if response in no_response:
calc = False
else:
response = input('\nRecalculate for another balance? (y/n): ')
while response not in yes_response + no_response:
again = input('Recalculate for another balance? (y/n): ')
if response in yes_response:
balance = int(input('\nEnter another balance: '))
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
25
This program will determine the time to pay off a credit
card and the interest paid based on the current balance,
the interest rate, and the monthly payments made.
Enter the balance on your credit card: 800
Enter the interest rate (APR) on the card: 12
Assuming a minimum payment of 2% of the balance ($20 min)
Your minimum payment would be 20.00
Use the minimum monthly payment? (y/n): n
Enter monthly payment: 75
PAYOFF SCHEDULE
Year
Balance
1
733.00
665.33
596.98
527.95
458.23
387.81
316.69
244.86
172.31
99.03
25.02
0.00
Payment Num
1
2
3
4
5
6
7
8
9
10
11
12
Interest Paid
8.00
15.33
21.98
27.95
33.23
37.81
41.69
44.86
47.31
49.03
50.02
50.27
Do you wish to do another calculation? (y/n): y
Recalculate for another balance? (y/n): y
Enter another balance: 500
Assuming a minimum payment of 2% of the balance ($20 min)
Your minimum payment would be 20.00
Use the minimum monthly payment? (y/n): n
Enter monthly payment: 75
PAYOFF SCHEDULE
Year
Balance
1
430.00
359.30
287.89
215.77
142.93
69.36
0.00
Payment Num
1
2
3
4
5
6
7
Interest Paid
5.00
9.30
12.89
15.77
17.93
19.36
20.05
Do you wish to do another calculation? (y/n): n
>>>
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
26
SOLUTIONS TO PROGRAM DEVELOPMENT PROBLEMS
D1. Metric Conversion Program
Develop and test a Python program that allows the user to convert between the metric
measurements of millimeter, centimeter, meter, kilometer, and inches, feet, yards, and miles. The
program should be written so that any one measurement can be converted to the other.
# Metric Conversion Program
# Problem D1 (Chapter 5)
# This program will convert between the metric measurements of millimeters,
# centimeters, meters, kilometers and English units of inches, feet, yards,
# and miles.
def displayWelcome():
print('This program will convert between metric and English units',
'of linear measure.')
print('\nMeasurements entered as <number><space><units>, where',
'<units> one of:')
print('METRIC UNITS: ', end='')
print('mm (millimters), cm (centimeters), m (meters), km (kilometers)')
print('\nENGLISH UNITS: ', end='')
print('ins (inches), ft (feet), yds (yards), mi (miles)')
def getMeasurement():
valid_input = False
while not valid_input:
measurement = input('\nEnter measurement: ')
# check if blank included (and not first/last character entered)
if not blank_char in measurement or \
measurement.index(blank_char) == 0 or \
measurement.index(blank_char) == len(measurement) - 1:
print('Must be of form <number><space><units>')
else:
# parse numeric and units info
numeric = measurement[0:measurement.index(blank_char)]
units = measurement[measurement.index(blank_char) + 1:]
# check that numeric part contains only digits and decimal point
invalidated_numeric = False
k = 0
while not invalidated_numeric and k < len(numeric):
if numeric[k] not in digit_chars + ('.',):
print('Invalid numeric value found')
print('Must be of form <number><space><units>')
invalidated_numeric = True
else:
k = k + 1
# check that units one of mm, cm, m, km, in, ft, yrds, mi
if not invalidated_numeric:
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
27
invalidated_units = False
if units not in available_units:
print('Invalid units found')
print('Must be of form <number><space><units>,')
print('for units one of mm, cm, m, km, in, ft, yds, mi')
invalidated_units = True
if not invalidated_numeric and not invalidated_units:
valid_input = True
return (int(numeric), units)
def displayConversion(current_measure, current_units, new_units, units_info):
units = units_info[0]
conversions = units_info[1]
current_conv_factor = conversions[units.index(current_units)]
new_conv_factor = conversions[units.index(new_units)]
new_measure = (current_conv_factor * current_measure) / new_conv_factor
print(current_measure, current_units, '=',
format(new_measure, '.2f'), new_units)
# ---- main
# init
blank_char = ' '
digit_chars = ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
available_units = ('mm', 'cm', 'm', 'km', 'in', 'ft', 'yds', 'mi')
conversions = (1, 10, 1000, 1e6, 25.4, 304.8, 914.4, 1.609344e6)
# display program welcome
displayWelcome()
# execute conversions
quit = False
while not quit:
# get measurement
measurement, units = getMeasurement()
# get units to convert to
units_conversion = input('Enter units to convert to: ')
while units_conversion not in available_units:
print('Invalid units entered - Please reenter')
units_conversion = input('Enter units to convert to: ')
# display conversion
displayConversion(measurement, units, units_conversion,
(available_units, conversions))
# continue?
response = input('\nDo you wish to do another conversion? (y/n) ')
while response not in ('Y', 'N', 'y', 'n'):
response = input('Do you wish to do another conversion? (y/n) ')
if response in ('N', 'n'):
quit = True
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
28
This program will convert between metric and English units of linear measure.
Measurements entered as <number><space><units>, where <units> one of:
METRIC UNITS: mm (millimters), cm (centimeters), m (meters), km (kilometers)
ENGLISH UNITS: ins (inches), ft (feet), yds (yards), mi (miles)
Enter measurement: 1 cm
Enter units to convert to: mm
1 cm = 10.000000 mm
Do you wish to do another conversion? (y/n) y
Enter measurement: 1 in
Enter units to convert to: cm
1 in = 2.540000 cm
Do you wish to do another conversion? (y/n) y
Enter measurement: 1 mi
Enter units to convert to: ft
1 mi = 5280.000000 ft
Do you wish to do another conversion? (y/n) y
Enter measurement: 1 mm
Enter units to convert to: mi
1 mm = 0.000001 mi
Do you wish to do another conversion? (y/n) y
Enter measurement: 1 km
Enter units to convert to: mi
1 km = 0.621371 mi
Do you wish to do another conversion? (y/n) n
>>>
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
29
D2. GPA Projection Program
Develop and test a Python program that lets the user enter their current cumulative GPA, their
total credits earned, and the number of credits they are currently taking. The program should then
request from the user a target cumulative GPA that they wish to achieve, and display the GPA of
the current semester needed to achieve it.
# Problem D2 (Chapter 5)
# This program will allow a student to determine what GPA is needed for the
# current semester to attain a specific cumulative GPA.
def convertGrade(grade):
if grade == 'F':
return 0
else:
return 4 - (ord(grade) - ord('A'))
def getGrades():
semester_info = []
more_grades = True
empty_str = ''
while more_grades:
course_grade = input('Enter grade (hit Enter if done): ')
while course_grade not in ('A','B','C','D','F',empty_str):
course_grade = input('Enter letter grade received: ')
if course_grade == empty_str:
more_grades = False
else:
num_credits = int(input('Enter number of credits: '))
semester_info.append([num_credits, course_grade])
return semester_info
# ---- main
# program greeting
print('This program will determine the current semester GPA needed' + \
'to attain \na specific cumulative GPA.')
# get current GPA info
total_credits = int(input('\nEnter total number of earned credits: '))
cumulative_gpa = float(input('Enter your current cumulative GPA: '))
# get current semester grade info
print()
current_sem_credits = \
(int(input('Enter total number of credits for this semester: ')))
target_cumulative_gpa = float(input('Enter target cummulative GPA: '))
# calculate required semester GPA
req_semester_gpa = \
(target_cumulative_gpa * (total_credits + current_sem_credits) - \
(cumulative_gpa * total_credits)) / current_sem_credits
Introduction to Computer Science Using Python – Dierbach
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30
# check if new cumulative GPA attainable
if req_semester_gpa > 4.0:
highest_cumulative_gpa = (cumulative_gpa * total_credits + \
4.0 * current_sem_credits) / +\
(total_credits + current_sem_credits)
print('The highest cummulative GPA you can achieve this semester is',
format(highest_cumulative_gpa, '.2f'))
else:
print('\nIn order to attain a new cumulative GPA of',
target_cumulative_gpa,
',\nyour GPA this', 'semester must be',
format(req_semester_gpa, '.2f'), 'or better.')
This program will determine the current semester GPA neededto attain
a specific cumulative GPA.
Enter total number of earned credits: 30
Enter your current cumulative GPA: 3.2
Enter total number of credits for this semester: 15
Enter target cummulative GPA: 3.4
In order to attain a new cumulative GPA of 3.4 ,
your GPA this semester must be 3.80 or better.
>>> ================================ RESTART ================================
>>>
This program will determine the current semester GPA neededto attain
a specific cumulative GPA.
Enter total number of earned credits: 60
Enter your current cumulative GPA: 3.35
Enter total number of credits for this semester: 15
Enter target cummulative GPA: 3.5
The highest cummulative GPA you can achieve this semester is 3.48
>>>
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
31
D3. Tic-Tac-Toe Two-Player Program
Develop and test a Python program that lets two players play tic-tac-toe. Let player 1 be X and
player 2 be O. Devise a method for each player to indicate where they wish to place their symbol.
The program should terminate if either there is a winner, or if the game results in a tie. The tic-tactoe board should be displayed after every move as shown below.
# Problem D3 (Chapter 5)
# This program will allow two players to play the game of tic-tac-toe.
def displayBoard(board):
empty_str = ''
for k in range(0, len(board)):
symbol = board[k]
if symbol == empty_str:
symbol = '-'
print(format(symbol, '^3'), end='')
if (k + 1) % 3 == 0:
print()
print()
def getMove(board, locations, player):
empty_str = ''
valid_move = False
while not valid_move:
move = input(player + ', ' + 'enter your move: ')
if move not in locations:
print('Must enter 1 .. 9')
elif board[int(move) - 1] != empty_str:
print('That location of the board already used')
else:
valid_move = True
return move
def win(board, symbol):
empty_str = ''
player_win = False
if symbol == 'X':
winning_sum = 6
else:
winning_sum = 3
# recreate board with 1 for 'X' and 0 for 'O'
alt_board = [2 if k == 'X' else 1 if k == 'O' else 0 for k in board]
# search board for win
k = 0
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
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while not player_win and k < 9:
# row win?
if alt_board[k] + alt_board[k + 1] + alt_board[k + 2] == winning_sum:
player_win = True
else:
k = k + 3
if not player_win:
k = 0
while not player_win and k < 3: # col win?
if alt_board[k] + alt_board[k + 3] + alt_board[k + 6] == winning_sum:
player_win = True
else:
k = k + 1
if not player_win: # diag win?
if alt_board[0] + alt_board[4] + alt_board[8] == winning_sum or \
alt_board[2] + alt_board[4] + alt_board[6] == winning_sum:
player_win = True
return player_win
def tieGame(board):
empty_str = ''
tie_game = True
for loc in board:
if loc == empty_str:
tie_game = False
return tie_game
# ---- main
# init
empty_str = ''
board = [empty_str for k in range(1, 10)]
locations = [str(x) for x in range(1,10)]
# program greeting
print('This program will allow two players to play the game of tic-tac-toe.')
print("Player 1 has 'X', and player 2 has 'O'.")
# get players
name_player1 = input('Enter the name of player 1: ')
name_player2 = input('Enter the name of player 2: ')
# display board locations
print('Enter your mark using the board positions shown below.\n')
displayBoard(locations)
# start game
player = name_player1
player_symbol = 'X'
print(name_player1, "you start. You are playing 'X'")
displayBoard(board)
game_over = False
while not game_over:
move = getMove(board,locations, player)
board[int(move) - 1] = player_symbol
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
33
displayBoard(board)
if win(board, player_symbol):
print(player + ', ' + 'you win!')
game_over = True
elif tieGame(board):
print('Tie Game!')
game_over = True
else:
if player == name_player1:
player = name_player2
player_symbol = '0'
else:
player = name_player1
player_symbol = 'X'
This program will allow two players to play the game of tic-tac-toe.
Player 1 has 'X', and player 2 has 'O'.
Enter the name of player 1: Chuck
Enter the name of player 2: Steve
Enter your mark using the board positions shown below.
1
4
7
2
5
8
3
6
9
Chuck you start. You are playing 'X'
- - - - - - Chuck,
X - - -
enter your move: 1
-
Steve,
X 0 - -
enter your move: 4
-
Chuck, enter your move: 1
That location of the board already used
Chuck, enter your move: 2
X X 0 - - - Steve,
X X
0 0
- -
enter your move: 5
-
Chuck,
X X
0 0
- -
enter your move: 9
X
Steve,
X X
0 0
0 -
enter your move: 7
X
Chuck,
X X
0 0
0 -
enter your move: 3
X
X
Chuck you win!
>>>
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
34
D4. Tic-Tac-Toe Automated Play
(solution omitted)
Introduction to Computer Science Using Python – Dierbach
Copyright 2013 John Wiley and Sons
35