What will we be doing?

• In this chapter, you'll learn how to write functions, which are blocks of code designed to perform specific tasks. Functions allow you to reuse code by calling the function whenever you need it, instead of rewriting the same code multiple times. This makes your programs easier to write, read, test, and fix. You'll also explore different ways to pass information to functions, create functions that display information or return values, and store functions in separate files, called modules, to keep your programs organized.

How Do Functions Work?

SYNTAX:

• • We use the keyword def to define the function and give it a name

    • • We also have to include ( ): after the name of the function

        • • For now, the brackets are empty, as the function does not need any information

          • This will change later. We can give functions information (ARGUMENTS) that it can use too!!

• Anything we want the function to do HAS TO BE INDENTED

  • • The function's body, indented after the definition, contains the actual code

• Once we define it, we can do tasks inside the function

  • • • This example was simple... it just prints a statement

Calling It...

• In order to USE the function, we call it later by using it's name

  • • This is known as a FUNCTION CALL and it tells Python to use the code inside the function

    • Note that it is called at the same indent level as it is defined!!!

What happens if we want a function that we write to not just run its own code, but to run code from another function? Can we do that??

YES! But ORDER MATTERS

How Does Python Execute Code?

• Python Reads Code Top-to-Bottom:

  • A function must be defined before it is called in the code. 

  • If you try to call a function that hasn't been defined yet, you'll get a NameError.

• Order of Function Definitions:

  • If a function A calls another function B, B must be defined above or before A is executed

Your Task:

• You must write the following functions:

  • • A Function that Welcomes The Guests to Jurassic Park - welcome_visitors()

      • • • This prints a fun Jurassic Welcome Message

    • A Function that Unlocks the gates to the park

      • • • Write a function called unlock_gates which tells the user the gates are being unlocked

    • A Function which Checks on the dinosaurs to ensure they’re secure.

      • • • Write a function called check_dinosaurs()

          • Add some fun logic to tell you if they're secure or not. Maybe a die roll??

    • A Function which Starts park operations to make the park fully operational.

      • • Name this function start_park_operations()

        • This function has to call the other functions...Write a function called start_park_operations which does the following:

          • • • Welcomes the Guests

              • Unlocks The Gates

              • Checks Dinosaurs

              • Prints a Final Message that the park is ready for visitors

Passing Information into a Function

• Our last function didn't require any extra information to run. When we called it, it just printed a nice message.

• Sometimes, we need to pass information into a function for it to do what we want. 

• SCENARIO: What if we want a function to greet a person by name??

  • • Do we know the name, or have to print out every possible option? 

    • Of COURSE we don't know the name. So, let's pass the name in!!!

Let's Try This Together: Print a Greeting:

#define a function which requires a name to be passed in

def print_greeting(username):

print(f"\nHello, {username.title()})

#Call the function with a specific name

print_greeting('Mr. Mac')

EXPLAIN THIS:

• • username is a parameter - The piece of information needed

  • 'Mr. Mac' is an argument - The actual information passed in

  • 'Mr. Mac' is then assigned to username when the function is called

    • • Every time we see username in the function, it's really 'Mr. Mac'