How to Think Like a Computer Scientist: Interactive Edition

This interactive book is a product of the Runestone Interactive Project at Luther College, led by Brad Miller and David Ranum. There have been many contributors to the project. Our thanks especially to the following:

• This book is based on the Original work by: Jeffrey Elkner, Allen B. Downey, and Chris Meyers

• Activecode based on Skulpt

• Codelens based on Online Python Tutor

• Many contributions from the CSLearning4U research group at Georgia Tech.

• ACM-SIGCSE for the special projects grant that funded our student Isaac Dontje Lindell for the summer of 2013.

• NSF

The Runestone Interactive tools are open source and we encourage you to contact us, or grab a copy from GitHub if you would like to use them to write your own resources.

Table of Contents

• Assignments

• 1. General Introduction
  • 1.1. The Way of the Program
  • 1.2. Algorithms
  • 1.3. The Python Programming Language
  • 1.4. Executing Python in this Book
  • 1.5. More About Programs
  • 1.6. What is Debugging?
  • 1.7. Syntax errors
  • 1.8. Runtime Errors
  • 1.9. Semantic Errors
  • 1.10. Experimental Debugging
  • 1.11. Formal and Natural Languages
  • 1.12. A Typical First Program
  • 1.13. Comments
  • 1.14. Glossary
  • 1.15. Exercises
• 2. Simple Python Data
  • 2.1. Variables, Expressions and Statements
  • 2.2. Values and Data Types
  • 2.3. Type conversion functions
  • 2.4. Variables
  • 2.5. Variable Names and Keywords
  • 2.6. Statements and Expressions
  • 2.7. Operators and Operands
  • 2.8. Input
  • 2.9. Order of Operations
  • 2.10. Reassignment
    • 2.10.1. Developing your mental model of How Python Evaluates
  • 2.11. Updating Variables
  • 2.12. Glossary
  • 2.13. Exercises
• 3. Debugging Interlude 1
  • 3.1. How to be a Successful Programmer
  • 3.2. How to Avoid Debugging
  • 3.3. Beginning tips for Debugging
  • 3.4. Know Your Error Messages
    • 3.4.1. ParseError
    • 3.4.2. TypeError
    • 3.4.3. NameError
    • 3.4.4. ValueError
  • 3.5. Summary
  • 3.6. Exercises
• 4. Python Turtle Graphics
  • 4.1. Hello Little Turtles!
  • 4.2. Our First Turtle Program
  • 4.3. Instances — A Herd of Turtles
  • 4.4. The for Loop
  • 4.5. Flow of Execution of the for Loop
  • 4.6. Iteration Simplifies our Turtle Program
  • 4.7. The range Function
  • 4.8. A Few More turtle Methods and Observations
  • 4.9. Summary of Turtle Methods
  • 4.10. Glossary
  • 4.11. Exercises
• 5. Python Modules
  • 5.1. Modules and Getting Help
  • 5.2. More About Using Modules
  • 5.3. The math module
  • 5.4. The random module
  • 5.5. Creating Modules
  • 5.6. Glossary
  • 5.7. Exercises
• 6. Functions
  • 6.1. Functions
  • 6.2. Functions that Return Values
  • 6.3. Unit Testing
    • 6.3.1. assert with for loops
    • 6.3.2. Return Value Tests
  • 6.4. Variables and Parameters are Local
  • 6.5. The Accumulator Pattern
    • 6.5.1. The General Accumulator Pattern
    • 6.5.2. A Variation on the Accumulator Pattern
  • 6.6. Functions can Call Other Functions
  • 6.7. Flow of Execution Summary
  • 6.8. Using a Main Function
  • 6.9. Program Development
  • 6.10. Composition
  • 6.11. A Turtle Bar Chart
  • 6.12. Glossary
  • 6.13. Exercises
• 7. Selection
  • 7.1. Boolean Values and Boolean Expressions
  • 7.2. Logical operators
    • 7.2.1. Logical Opposites
  • 7.3. Precedence of Operators
  • 7.4. Conditional Execution: Binary Selection
  • 7.5. Omitting the else Clause: Unary Selection
  • 7.6. Nested conditionals
  • 7.7. Chained conditionals
  • 7.8. Boolean Functions
    • 7.8.1. More Unit Testing
  • 7.9. Glossary
  • 7.10. Exercises
• 8. More About Iteration
  • 8.1. Iteration Revisited
  • 8.2. The for loop revisited
  • 8.3. The while Statement
  • 8.4. Randomly Walking Turtles
  • 8.5. The 3n + 1 Sequence
  • 8.6. Newton’s Method
  • 8.7. The Accumulator Pattern Revisited
  • 8.8. Other uses of while
    • 8.8.1. Sentinel Values
    • 8.8.2. Validating Input
  • 8.9. Algorithms Revisited
  • 8.10. Simple Tables
  • 8.11. 2-Dimensional Iteration: Image Processing
    • 8.11.1. The RGB Color Model
    • 8.11.2. Image Objects
    • 8.11.3. Image Processing and Nested Iteration
  • 8.12. Image Processing on Your Own
  • 8.13. Glossary
  • 8.14. Exercises
• 9. Strings
  • 9.1. Strings Revisited
  • 9.2. A Collection Data Type
  • 9.3. Operations on Strings
  • 9.4. Index Operator: Working with the Characters of a String
  • 9.5. String Methods
    • 9.5.1. String Format Method
  • 9.6. Length
  • 9.7. The Slice Operator
  • 9.8. String Comparison
  • 9.9. Strings are Immutable
  • 9.10. Traversal and the for Loop: By Item
  • 9.11. Traversal and the for Loop: By Index
  • 9.12. Traversal and the while Loop
  • 9.13. The in and not in operators
  • 9.14. The Accumulator Pattern with Strings
  • 9.15. Turtles and Strings and L-Systems
  • 9.16. Looping and Counting
  • 9.17. A find function
  • 9.18. Optional parameters
  • 9.19. Character classification
  • 9.20. Summary
  • 9.21. Glossary
  • 9.22. Exercises
• 10. Lists
  • 10.1. Lists
  • 10.2. List Values
  • 10.3. List Length
  • 10.4. Accessing Elements
  • 10.5. List Membership
  • 10.6. Concatenation and Repetition
  • 10.7. List Slices
  • 10.8. Lists are Mutable
  • 10.9. List Deletion
  • 10.10. Objects and References
  • 10.11. Aliasing
  • 10.12. Cloning Lists
  • 10.13. Repetition and References
  • 10.14. List Methods
  • 10.15. The Return of L-Systems
  • 10.16. Append versus Concatenate
  • 10.17. Lists and for loops
  • 10.18. The Accumulator Pattern with Lists
    • 10.18.1. Accumulating the Max Value
    • 10.18.2. Accumulating a String Result
  • 10.19. Using Lists as Parameters
  • 10.20. Pure Functions
  • 10.21. Which is Better?
  • 10.22. Functions that Produce Lists
  • 10.23. List Comprehensions
  • 10.24. Nested Lists
  • 10.25. Strings and Lists
  • 10.26. list Type Conversion Function
  • 10.27. Tuples and Mutability
  • 10.28. Tuple Assignment
  • 10.29. Tuples as Return Values
  • 10.30. Glossary
  • 10.31. Exercises
• 11. Files
  • 11.1. Working with Data Files
  • 11.2. Finding a File on your Disk
  • 11.3. Reading a File
  • 11.4. Iterating over lines in a file
  • 11.5. Alternative File Reading Methods
  • 11.6. Writing Text Files
  • 11.7. With Statements
  • 11.8. Fetching Something From The Web
  • 11.9. Glossary
  • 11.10. Exercises
• 12. Dictionaries
  • 12.1. Dictionaries
  • 12.2. Dictionary Operations
  • 12.3. Dictionary Methods
  • 12.4. Aliasing and Copying
  • 12.5. Sparse Matrices
  • 12.6. Glossary
  • 12.7. Exercises
• 13. Exceptions
  • 13.1. What is an exception?
  • 13.2. Exception Handling Flow-of-control
    • 13.2.1. Raising and Catching Errors with try and except
  • 13.3. Runetime Stack and raise command
  • 13.4. Summary
  • 13.5. Standard Exceptions
  • 13.6. Principles for using Exceptions
  • 13.7. Exceptions Syntax
    • 13.7.1. Catch All Exceptions
    • 13.7.2. Catch A Specific Exception
    • 13.7.3. Catch Multiple Specific Exceptions
    • 13.7.4. Clean-up After Exceptions
    • 13.7.5. An Example of File I/O
  • 13.8. The finally clause of the try statement
  • 13.9. Glossary
  • 13.10. Exercises
• 14. Web Applications
  • 14.1. Web Applications
  • 14.2. How the Web Works
  • 14.3. How Web Applications Work
  • 14.4. Web Applications and HTML Forms
  • 14.5. Writing Web Applications With Flask
  • 14.6. More About Flask
  • 14.7. Input For A Flask Web Application
  • 14.8. Web Applications With a User Interface
  • 14.9. Glossary
• 15. GUI and Event Driven Programming
  • 15.1. Graphical User Interfaces
  • 15.2. GUI Programming
  • 15.3. GUI Programming Options
  • 15.4. TKinter
  • 15.5. Tkinter Pre-programmed Interfaces
  • 15.6. Tkinter Custom Interfaces
  • 15.7. Hello World
  • 15.8. Tkinter Standard Dialog Boxes
    • 15.8.1. Messages
    • 15.8.2. Yes/No Questions
    • 15.8.3. Single Value Data Entry
    • 15.8.4. File Chooser
    • 15.8.5. Color Chooser
  • 15.9. GUI Widgets
  • 15.10. Creating Widgets
  • 15.11. Layout Mangers
  • 15.12. Specifying Dimensions
  • 15.13. Place Layout Manager
  • 15.14. Grid Layout Manager
  • 15.15. Pack Layout Manager
    • 15.15.1. Summary
  • 15.16. Widget Groupings
  • 15.17. Command Events
  • 15.18. Hello World Again
  • 15.19. Other Events
  • 15.20. Low-Level Event Processing
  • 15.21. Focus
  • 15.22. Event Binding
  • 15.23. Event Descriptors
  • 15.24. Event Objects
  • 15.25. Event Processing
  • 15.26. The Design of GUI Programs
  • 15.27. Common Widget Properties
  • 15.28. Specific Widget Properties
  • 15.29. Widget Attributes
  • 15.30. Timer Events
    • 15.30.1. Animations and Repeated Tasks
    • 15.30.2. Canceling Timer Events
    • 15.30.3. Multiple Parameters to Timer Callbacks
  • 15.31. A Programming Example
    • 15.31.1. A Whack-a-mole Game
    • 15.31.2. Summary
  • 15.32. Managing GUI Program Complexity
    • 15.32.1. Creating the View
    • 15.32.2. Creating the Model
    • 15.32.3. Creating the Controller
  • 15.33. Exercises
  • 15.34. Glossary
• 16. Recursion
  • 16.1. What Is Recursion?
  • 16.2. Calculating the Sum of a List of Numbers
  • 16.3. The Three Laws of Recursion
  • 16.4. Converting an Integer to a String in Any Base
  • 16.5. Visualizing Recursion
  • 16.6. Sierpinski Triangle
  • 16.7. Glossary
  • 16.8. Programming Exercises
  • 16.9. Exercises
• 17. Classes and Objects - the Basics
  • 17.1. Object-oriented programming
  • 17.2. A change of perspective
  • 17.3. Objects Revisited
  • 17.4. User Defined Classes
  • 17.5. Improving our Constructor
  • 17.6. Adding Other Methods to our Class
  • 17.7. Objects as Arguments and Parameters
  • 17.8. Converting an Object to a String
  • 17.9. Instances as Return Values
  • 17.10. Glossary
  • 17.11. Exercises
• 18. Classes and Objects - Digging a Little Deeper
  • 18.1. Fractions
  • 18.2. Objects are Mutable
  • 18.3. Sameness
  • 18.4. Arithmetic Methods
  • 18.5. Glossary
  • 18.6. Exercises
• 19. Inheritance
  • 19.1. Pillars of OOP
  • 19.2. Introduction to Inheritance
  • 19.3. Extending
  • 19.4. Reuse Through Composition
  • 19.5. Class Diagrams
  • 19.6. Composition vs. Inheritance
  • 19.7. Case Study: Structured Postal Addresses
    • 19.7.1. Storing Postal Addresses
    • 19.7.2. Storing International Addresses
    • 19.7.3. Inheritance Applied
    • 19.7.4. A List of Addresses
    • 19.7.5. Using isinstance
• 20. Unit Testing
  • 20.1. Introduction: Unit Testing
  • 20.2. Checking Assumptions With assert
    • 20.2.1. Designing Defensive Functions
    • 20.2.2. The assert Statement
    • 20.2.3. More on assert and Preconditions
  • 20.3. Testing Functions
    • 20.3.1. Automated Unit Tests
    • 20.3.2. Automated Unit Tests with assert
    • 20.3.3. Unit Tests can have bugs
  • 20.4. Designing Testable Functions
    • 20.4.1. Design by Contract
  • 20.5. Writing Unit Tests
    • 20.5.1. Specification-Based Testing
  • 20.6. Test-First Development
    • 20.6.1. Benefits of Test-First Development
  • 20.7. Testing with pytest
    • 20.7.1. Organizing pytest Functions
    • 20.7.2. Using pytest
    • 20.7.3. Understanding pytest Failure Reports
    • 20.7.4. Integrated Unit Testing with pytest
  • 20.8. Glossary
  • 20.9. Exercises
• 21. Hidden Items

Labs

Labs

• Astronomy Animation
• Turtle Racing Lab
• Drawing a Circle
• Lessons from a Triangle
• Finally a Circle
• Counting Letters
• Letter Count Histogram
• Approximating the Value of Pi
• Python Beyond the Browser
• Experimenting With the 3n+1 Sequence
• Plotting a sine Wave

Appendices

Appendices

• Debugging
• Using Python in an IDE
• Operator precedence table
• test module source code

Acknowledgements

Acknowledgements

• Copyright Notice
• Preface to the Interactive Edition
• Whats the deal with Logging in?
• How to Contribute
• Acknowledgements
• Foreword
• Preface to the Third Edition
• The Rhodes Local Edition (RLE)
• Preface to the First and Second Editions
• Contributor List
• GNU Free Documentation License
• ADDENDUM: How to use this License for your documents

Index and Search

• Index

• Search Page

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