Head First Learn to Code

Praise for Head First Learn to Code
Praise for other books by Eric Freeman
Head First Learn to Code
The author
Table of Contents (the real thing)

Intro
Who is this book for?
Who should probably back away from this book?
We know what you’re thinking.
And we know what your brain is thinking.
Metacognition: thinking about thinking
So how DO you get your brain to think coding is as important as a tiger?
Here’s what WE did:
Here’s what YOU can do to bend your brain into submission
Read Me
We want you to learn the thinking process behind programming.
In this book we use Python.
We don’t exhaustively cover every aspect of the Python language.
You can use a Mac or PC, or Linux for that matter.
The activities are NOT optional.
The redundancy is intentional and important.
The examples are as lean as possible.
The Brain Power exercises don’t usually have answers.
Get the code examples, help, and discussion online.
You’re going to have to install Python
A word on organizing your code
Acknowledgments*
The Review Team

1. thinking computationally: Getting Started
Breaking it down
How coding works
Are we even speaking the same language?
The world of programming languages
How you’ll write and run code with Python
there are no Dumb Questions
A very brief history of Python
Putting Python through its paces
Saving your work
Congrats on coding your first Python program!
there are no Dumb Questions
Phrase-O-Matic
Getting the code in the machine

2. simple values, variables, and types: Know Your Value
Coding the Dog Age Calculator
Going from pseudocode to code
Step 1: Getting some input
How the input function works
Using variables to remember and store values
Assigning the user’s input to a variable
Step 2: Getting more input
It’s time to run some code
Getting some code entered
A deep dive on variables
Adding some expression
Variables are called VARY-ables for a reason
Better living through operator precedence
Computing with operator precedence
Crack the Code Challenge
Back away from that keyboard!
there are no Dumb Questions
Step 3: Computing the dog’s age
Houston, we’ve got a problem!
To err is human to code
A little more debugging...
Careful what you ask for...
What are Python types, anyway?
there are no Dumb Questions
Fixing our code
there are no Dumb Questions
Houston, we have liftoff
Step 4: User-friendly output
Who am I? Solution
Crack the Code Challenge SOLUTION

3. booleans, decisions, and loops: Decisive Code
Would you like to play a game?
How Rock, Paper, Scissors works
How you’re going to play against the computer
First, a high-level design
The computer’s choice
How to generate a random number
How to use the random number
there are no Dumb Questions
Taking things further...
True? Or False?
Introducing the Boolean type
Making decisions
Decisions and more decisions
Back to Rock, Paper, Scissors
Getting the user’s choice
Good eye.
Taking a look at the user’s choice
Adding the code to detect a tie
Who won?
Right.
How to implement the game logic
More about Boolean operators
Display the winner
Got documentation?
How to add comments to your code
We need to finish that game!
How do we know if the user’s choice is invalid?
Checking out and cleaning up the expression
How to continually prompt the user
Doing things more than once
How the while loop works
How to use while to prompt the user until you get a valid choice
Congratulations on coding your first game!
Beware of the The Dreaded Infinite Loop

4. lists and iteration: Providing Some Structure
Can you help Bubbles-R-Us?
How to represent multiple values in Python
How lists work
How to create a list
How to access a list item
Updating a value in the list
How big is that list, anyway?
Accessing the last item in the list
Python makes this even easier
Using Python’s negative indices
there are no Dumb Questions
Meanwhile, back at Bubbles-R-Us...
Cubicle conversation
How to iterate over a list
Fixing the output glitch
Really fixing the output glitch
The for loop, the preferred way to iterate over a list
How the for loop works
How the for loop works on a range of numbers
Doing more with ranges
Try a starting and ending number
Add a step size
Count backward
Or start from negative numbers
there are Dumb Questions
Putting it all together
Test drive the bubble report
Fireside Chats
Cubicle conversation continued...
Building your own list, from scratch
Doing even more with lists
Delete an item from a list
Add one list to another
Or insert items into your list
there are no Dumb Questions
Test drive the final report
And the winners are...
Testing the most cost-effective solution
You’re right: we didn’t need to.

5. functions and abstraction: Getting Functional
What’s wrong with the code, anyway?
Turning a block of code into a FUNCTION
We created a function, so how do we use it?
But how does all this actually work?
there are no Dumb Questions
Functions can RETURN things too
How to call a function that has a return value
Good catch.
Getting a little refactoring under our belts
Running the code
How to abstract the avatar code
Writing the get attribute function body
Calling get attribute
Let’s talk about variables a little more...
Understanding variable scope
there are no Dumb Questions
When variables get passed to functions
Making the drink_me function call
What about using global variables in functions?
Fireside Chats
Going further with parameters: default values and keywords
How default parameter values work
Always list your required parameters first!
Using arguments with keywords
How to think about all these options
The case of the attempted robbery not worth investigating

4, part 2. sorting and nested iteration: Putting Some Order in Your Data
Cubicle conversation
Understanding bubble sort
Starting with pass 1
Pass 2
Pass 3
Some bubble sort pseudocode
Cubicle conversation continued...
Implementing bubble sort in Python
Computing bubble solution numbers

6. text, strings, and heuristics: Putting It All Together
Welcome to the data sciences
How do you compute something like readability?
The game plan
Writing some pseudocode
We need some text to analyze
How to get multiline text into Python
Setting up the function
First up: we need the total number of words in our text
Cubicle conversation
there are no Dumb Questions
Computing the total number of sentences
Writing the count_sentences function
Computing the number of syllables, or, learning to love heuristics
Cubicle conversation continued...
Setting up the heuristic
Writing the heuristic
How to count vowels
Ignoring consecutive vowels
Writing the code to ignore consecutive vowels
Removing final e’s, y’s, and punctuation
He who controls the slice, controls the...
Putting slicing (substrings) to work
Finishing off the heuristic code
Implementing the reading ease formula
Taking it even further

7. modules, methods, classes, and objects: Getting Modular
Cubicle conversation
A quick module review
there are no Dumb Questions
Cubicle conversation continued...
The name global variable
Cubicle conversation continued...
Updating analyze.py
Using analyze.py as a module
Adding docstrings to analyze.py
Exploring other Python modules
Wait, did someone say “turtles”?!
Creating your very own turtle
Turtle lab
there are no Dumb Questions
Adding a second turtle
What are turtles, anyway?
What are objects?
Okay, what’s a class then?
A class is not an object, it’s used to construct them.
there are no Dumb Questions
A class tells us what an object knows and what an object can do
How to use objects and classes
What about those methods and attributes?
Seeing classes and objects everywhere
Get ready for some turtle races
Planning the game
Let’s start coding
Setting up the game
Writing the setup code
Not so fast!
Starting the race
Don’t worry, this isn’t the end of objects.
Odd goings-on at the turtle races.
Mod coding cross
Mod cross Solution

8. recursion and dictionaries: Beyond Iteration and Indices
A different way to compute
And now the different way...
Now let’s write some code for our two cases
Let’s get some more practice
Using recursion to detect palindromes
Writing a recursive palindrome detector
there are no Dumb Questions
Fireside Chats
The Anti-Social Network
Introducing the dictionary
Let’s see how to create a dictionary
And then add items
And then retrieve values by their keys
Keys and values do not have to be strings
Of course you can remove keys as well
But you might want to test to see if it exists first
there are no Dumb Questions
What about iterating through a dictionary?
Okay, but can we get literal for a sec?
Leveraging dictionaries at the Anti-Social Network
But how do we add more attributes?
Remember the Anti-Social Network’s killer feature?
Finding the most anti-social user
Now, it’s all you!
Can we just remember function call results?
Using a dictionary to remember our Fibonacci results
We might as well use the $5 words: memoization
Some more brain building
A closer look at the koch function
Truly exploring the koch fractal
They don’t call it the Koch snowflake for nothin’

9. saving and retrieving files: Persistence
Ready for some Crazy Libs?
How to Play
How Crazy Libs is going to work
Step 1: Read the text of the story from a file
To read a file in Python, you first have to open it
How to use file paths
Relative paths
Absolute paths
Oh, and don’t forget to clean up when you’re done!
Reading a file into your Python code
Using the file object to read a file
Oh, give it a break already...
Hey, we’ve got a Crazy Lib game to finish!
Using the readline method of the file object
How do we know when we’ve read the last line?
Ah, but there’s a easier way using the power of Python sequences
Reading in a Crazy Lib template
Processing the template text
Now let’s process the text
Using a new string method to fix the bug
Actually fixing the bug
Some code has real problems
Handling exceptions
Explicitly handling exceptions
there are Dumb Questions
Updating Crazy Libs to handle exceptions
Our last step: storing the Crazy Lib
Updating the rest of the code
File i/o cross Solution

10. using web apis: You Really Should Get Out More
Extending your reach with Web APIs
How Web APIs work
All Web APIs have a web address
Consult the API documentation.
Good point.
Time for a quick upgrade
Doing the upgrade
there are no Dumb Questions
All we need now is a good Web API...
A closer look at the API
Web APIs provide data using JSON
there are no Dumb Questions
Now let’s look at that request module again
Putting it all together: making a request to Open Notify
How to use JSON in Python
Using the JSON module on our ISS data
Let’s add some graphics
Meet the screen object
Let’s add a turtle to represent the ISS
Turtles can look like space stations too
Forget the ISS—where are we?
Finishing off the ISS code

11. widgets, events, and emergent behavior: Getting Interactive
A closer look at the Game of Life
Oh, you’d be surprised...
What we’re going to build
Do we have the right design?
How we’re going to build the simulator
Building the data model
Representing the grid
Computing a generation of the Game of Life
Computing each cell’s fate
Completing the model code
Where are we?
Building the view
Creating your first widget
Adding the rest of the widgets
Correcting the layout
Placing the widgets into a grid layout
Translating the grid layout to code
there are no Dumb Questions
Moving on to the controller
Adding an update function
there are no Dumb Questions
Ready for another new style of computation?
Let’s add a click handler
How the start/pause button is going to work
Implementing the start/pause button
Another kind of event
We have the technology: the after method
Are we there yet?
How to enter and edit cells directly
Writing the grid_view handler
Now it’s time to add some patterns
Writing a handler for the OptionMenu
How to define your patterns
Writing the pattern loader

12. object-oriented programming: A Trip to Objectville
Breaking it down, a different way
What’s the point of object-oriented programming, anyway?
Designing your first class
Writing your first class
How the constructor works
there are no Dumb Questions
Writing the bark method
How methods work
Adding some inheritance
Implementing the ServiceDog class
A closer look at subclassing
A ServiceDog IS-A Dog
Testing IS-A in code
How would you describe yourself?
there are no Dumb Questions
Overriding and extending behavior
Welcome to Jargon City
Object can HAS-Another object
Designing a Doggie Hotel
Implementing the Doggie Hotel
Renovating the Doggie Hotel
Adding some hotel activities
I can do anything you can, or Polymorphism
It’s about time we teach the other dogs to walk
The power of inheritance
Creating a Doggie Hotel walking service
How are we going to hire a person to walk our dogs if we don’t even have people objects?
Meanwhile, back at the turtle races…
The turtle races case SOLVED
Have you considered a career in coding?

appendix: leftovers: The Top Ten Topics (We Didn’t Cover)
#1 List comprehensions
#2 Dates and times
#3 Regular expressions
#4 Other data types: tuples
#5 Other data types: sets
#6 Server-side coding
#7 Lazy evaluation
#8 Decorators
#9 Higher-order and first-class functions
#10 A lot of libraries

Don't worry, this isn't goodbye.

Index