Showing Revision 4 created 05/25/2016 by Udacity Robot.

1. Title:
   Updating the Design for Class Movie - Programming Foundations with Python
2. Description:

3. 290 0:00 - 0:02
   So in a previous lesson we created a class
4. 2350 0:02 - 0:06
   called movie. Now this class had the following attributes,
5. 5850 0:06 - 0:09
   the movie's title, its storyline, a link to the
6. 8875 0:09 - 0:11
   movie's poster image, and a link to its YouTube
7. 11460 0:11 - 0:15
   trailer. Now in addition to these things, the class
8. 14670 0:15 - 0:19
   movie also had a function called show_trailer. After we
9. 18690 0:19 - 0:22
   had defined this class movie we created several instances
10. 21800 0:22 - 0:26
    of this class. Instances like Toy Story and Avatar.
11. 25830 0:26 - 0:28
    Now further imagine that we wanted to create
12. 28270 0:28 - 0:32
    another class called TvShow. I would think that
13. 32390 0:32 - 0:35
    this class would have details like the title
14. 34970 0:35 - 0:39
    of the show, its season and episode number. And
15. 38620 0:39 - 0:41
    also, the TV station that this show is
16. 40770 0:41 - 0:44
    aired on. Additionally, this class could also have
17. 43690 0:44 - 0:47
    a function called, get_local_listings. Once we've created a
18. 47280 0:47 - 0:51
    class called TvShow, we can create multiple instances of
19. 51020 0:51 - 0:54
    this class, instances like, season one, episode one
20. 54440 0:54 - 0:59
    of Breaking Bad, and the final episode of Seinfeld.
21. 58820 0:59 - 1:01
    Alright, so if we continue our thought experiment
22. 61200 1:01 - 1:04
    here, we can further imagine that there can be
23. 63660 1:04 - 1:06
    several items that both of these classes can
24. 66280 1:06 - 1:10
    share amongst each other. Things like title for sure,
25. 70260 1:10 - 1:13
    also things like duration of the movie and
26. 72720 1:13 - 1:16
    duration of the TV show in minutes. So the
27. 76040 1:16 - 1:18
    best way to structure this code would be
28. 78240 1:18 - 1:21
    to create another class called Video, which would
29. 81120 1:21 - 1:24
    have two attributes. The video's title, and the
30. 83968 1:24 - 1:28
    video's duration. And the class Movie, could inherit from
31. 88490 1:28 - 1:31
    this class Video. To do this, we would
32. 91370 1:31 - 1:35
    have to add the class name Video, inside these
33. 94740 1:35 - 1:38
    parentheses. Now, this would mean that class Movie,
34. 98040 1:38 - 1:43
    would inherit title and duration, from class Video. Additionally,
35. 102720 1:43 - 1:46
    the class TvShow could also inherit from class
36. 106030 1:46 - 1:49
    Video. To do this we would also have
37. 108610 1:49 - 1:51
    to add the class name Video inside these
38. 111248 1:51 - 1:56
    parentheses. Now this would mean that class TvShow would
39. 115560 1:56 - 2:00
    inherit title and duration from class video. Now
40. 119760 2:00 - 2:02
    you can clearly see how we can write a
41. 121540 2:02 - 2:05
    piece of code. In this case, class Video,
42. 124570 2:05 - 2:08
    and continue to reuse it in multiple different places.
43. 128430 2:08 - 2:11
    Another big benefit of writing code this way,
44. 131400 2:11 - 2:14
    in addition to just reusing code, is that
45. 134330 2:14 - 2:18
    it allows us to follow an intuitive model
46. 137590 2:18 - 2:21
    of how things exist in our brain. So intuitively
47. 140970 2:21 - 2:27
    speaking, we know what videos are, we also know what TV shows and movies are. So
48. 147260 2:27 - 2:30
    writing code in this way allows programmers to
49. 150110 2:30 - 2:33
    map how things exist in our brain onto code.