1. COMP 171: Functions, for loops and range John Barr Section 03 Slides by Toby Dragon

2. What is a function? a block of code that we can call with a single name.  "Black Box" defined in order to provide functionality without dealing with how it works Some functions are provided to you:  input (), print () Some functions you have written:  drawRect(length, width)

3. Why functions? break code into smaller, functional pieces  testing parts before trying to solve everything  Make pieces that can be reused for multiple purposes simplify (abstract) to make your program easier to understand and to use

4. Functions: defining the "Black Box" def drawInitials (): Tell python we're defining a function "Name" that we decide place for parameters (empty if none) tells python that the function is starting, everything indented after this will be part of the function

5. Parameters def drawInitials (): def drawSquare (size): def drawRect (length, width): No parameters One parameter Two parameters

6. Parameters Parameters answer questions the function has.  e.g., drawRect needs to know the length and width of the rectangle you want drawn Use parameters only when necessary!

7. Practice Write a function that takes the temperature in Fahrenheit and prints the temperature in Celsius.  To calculate Celsius from Fahrenheit: subtract 32 multiply by 5/9

8. Practice Write a function that takes the temperature in Fahrenheit and prints the temperature in Celsius.  To calculate Celsius from Fahrenheit: subtract 32 multiply by 5/9

9. Functions: using the "Black Box" when we use a function, we say we are calling the function. Always end in parentheses!  Otherwise, python treats it as a variable Between parentheses you give values to the parameters

10. Calling functions and sending Parameters drawInitials () drawSquare (100) sides=100 ends = 200 drawInitials (sides, ends)

11. the for loop for num in range(0, 10, 1): indented code below it will happen multiple times, each with num = a number from the range. variable you create range function

12. Repetition: the range function range (10) – give each number, starting at 0 to less than 10 range (3, 10) – give each number, starting at 3 to less than 10 range (2, 20, 2) – give each number starting at 2, to less than 20, and count by 2 name of the range function Parameter(s)

13. Repetition: range practice [0, 1, 2, 3,..., 19] [2, 4, 6,..., 46, 48] [50, 48,..., 0]

14. Repetition: for loop practice Write a for loop that prints: 3 6 9 … 18

15. for loop practice Write a program to print the Celsius equivalent of every 10 degrees Fahrenheit between 0 and 100. Use your function from earlier!