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Course A201: Introduction to Programming

Course A201: Introduction to Programming. 11/11/2010. Outline for this week. Assignment 6 Recap for f unction Variable scope: global variable vs local variable Recursive function Assignment 8 Divide into two teams, come up with pseudo code then choose a partner. Recap.

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Course A201: Introduction to Programming

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  1. Course A201:Introduction to Programming 11/11/2010

  2. Outline for this week • Assignment 6 • Recap for function • Variable scope: global variable vs local variable • Recursive function • Assignment 8 • Divide into two teams, come up with pseudo code • then choose a partner

  3. Recap • Difference between return and print Ex: circle_area.py defcircle_area(radius): return (3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”)

  4. Recap I’m IDLE for a while… defcircle_area(radius): return (3.14159 * radius ** 2) circle_area(5) print (“Now I know the area of the circle”)

  5. Recap Below is my Memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print (“Now I know the area of the circle”) This region shows what I know before I starts to execute the program This region shows what I know during I’m executing the program

  6. Recap I know function circle_area ! defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius • Start to execute. • f- means function, p- means parameter

  7. Recap Program tells me that now the parameter radius is 5 defcircle_area(radius): return (3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius • (in f-circle_area) radius = 5 • Start to execute. • f- means function, p- means parameter

  8. Recap IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 This region of memory is only for function circle_area • Go to function • circle_area(radius)

  9. Recap IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 It will be erased when I finish executing the function • Go to function • circle_area(radius)

  10. Recap IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 radius = 5 • Go to function • circle_area(radius)

  11. Recap IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 radius = 5 return value = 78.53975 • Go to function • circle_area(radius)

  12. Recap IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 (f-circle_area) return value=78.53975 • Jump out of function circle_area

  13. Recap Nothing on screen IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 (f-circle_area) return value=78.53975 • Result stays in the memory of IDLE, but nothing will be shown on the screen

  14. Recap Now I know the area of the circle IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 (f-circle_area) return value=78.53975 Execute print • Finish executing the function, goes to the next line

  15. Recap Now I know the area of the circle IDLE’s memory defcircle_area(radius): return(3.14159 * radius ** 2) circle_area(5) print(“Now I know the area of the circle”) f-circle_area with p-radius (in f-circle_area) radius = 5 (f-circle_area) return value=78.53975 Execute print • The result is not stored in any variable, so it is lost! • Finish executing the function, goes to the next line

  16. Recap • Therefore, the correct way to call a function with a return statement is: result = circle_area(5) print(“Now I know the area of the circle:”, result) result = result * 2 print(“And also the area of 2 such circles:”, result)

  17. Let’s change to print • Difference between return and print Ex: circle_area.py defcircle_area(radius): print(3.14159 * radius ** 2) circle_area(5)

  18. Recap IDLE’s memory defcircle_area(radius): print(3.14159 * radius ** 2) circle_area(5) f-circle_area with p-radius (in f-circle_area) radius = 5 radius = 5 • Go to function • circle_area(radius)

  19. Recap 78.53975 I am asked to print a value defcircle_area(radius): print(3.14159 * radius ** 2) circle_area(5) f-circle_area with p-radius (in f-circle_area) radius = 5 radius = 5 • Screen shows: • 78.53975

  20. Recap 78.53975 IDLE’s memory defcircle_area(radius): print(3.14159 * radius ** 2) circle_area(5) f-circle_area with p-radius (in f-circle_area) radius = 5 radius = 5 return value = None • Screen shows: • 78.53975

  21. Recap 78.53975 IDLE’s memory defcircle_area(radius): print(3.14159 * radius ** 2) circle_area(5) f-circle_area with p-radius (in f-circle_area) radius = 5 (f-circle_area) return value is None • Jump out of function circle_area, no return value

  22. Recap 78.53975 IDLE’s memory defcircle_area(radius): print(3.14159 * radius ** 2) circle_area(5) f-circle_area with p-radius (in f-circle_area) radius = 5 (f-circle_area) return value is None • Jump out of function circle_area, no return value

  23. Notice • What shows on the screen does not equal with what IDLE knows/keeps in its memory • When you write all codes in a file and execute it by pressing F5, IDLE will not show what it knows onto the screen unless you tell it to, using print

  24. Recap [parameter] • A special kind of variable • In the parentheses of function definition, separated by commas ex: defcircle_area(radius): defprint_heading(title):

  25. Recap [argument] • The values in the parentheses in function calls • Each value then is assigned to the corresponding parameter ex: defcircle_area(radius): …… print(circle_area(5)) • This is a function call

  26. Recap [argument] • The values in the parentheses in function calls • Each value then is assigned to the corresponding parameter ex: defcircle_area(radius): …… print(circle_area(5)) • “5” is the argument

  27. Recap [argument] • The values in the parentheses in function calls • Each value then is assigned to the corresponding parameter ex: defcircle_area(radius): …… print(circle_area(5)) • Then radius is assigned with value 5 in the function of cricle_area

  28. Recap [argument] • The values in the parentheses in function calls • Each value then is assigned to the corresponding parameter ex: defcircle_area(r1, r2, r3): …… print(circle_area(5, 6, 7)) • In the same way: • r1 is assigned 5 • r2 is assigned 6 • r3 is assigned 7

  29. Recap [default parameter values] defbirthday1(name= “Jackson”,age=1): print(“Happy birthday,”, name, “!”, “ I hear you're”, age, “today.\n”) >>>birthday1(‘Mary’, 2) Happy birthday, Mary ! I hear you are 2 today. >>>birthday1() Happy birthday, Jackson ! I hear you are 1 today.

  30. Variable scope • See lecture slides: Global variable and Local variable • Let’s see an example

  31. Recursive Function • See lecture slides: Recursive Function

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