1
00:00:00,290 --> 00:00:04,650
With our database ready to go, we need
to start building out our application.

2
00:00:04,650 --> 00:00:06,640
Let's start with the menu function.

3
00:00:06,640 --> 00:00:10,693
It'll print out the menu options
to the console, ask the user for

4
00:00:10,693 --> 00:00:15,496
their choice, and then return their
choice for use in our main app function.

5
00:00:20,263 --> 00:00:21,820
Couple spaces.

6
00:00:23,630 --> 00:00:30,660
def menu and then inside we're
going to create a while loop.

7
00:00:31,980 --> 00:00:34,810
Do while True.

8
00:00:34,810 --> 00:00:37,360
And then let's print out our menu options.

9
00:00:37,360 --> 00:00:40,675
Print, two, three, four, five, six, and

10
00:00:40,675 --> 00:00:44,760
I'm doing the triple so
that we can do multi-line here.

11
00:00:46,300 --> 00:00:52,679
And let's do, I'm gonna do caps lock,
PROGRAMMING BOOKS.

12
00:00:55,815 --> 00:00:57,960
1 is going to be Add book.

13
00:00:59,210 --> 00:01:02,620
2 is going to be View all books.

14
00:01:03,830 --> 00:01:08,823
3, Search for book.

15
00:01:08,823 --> 00:01:13,359
4, Book analysis,

16
00:01:13,359 --> 00:01:16,639
and 5, Exit.

17
00:01:16,639 --> 00:01:20,430
Great, and let's do the input, too.

18
00:01:20,430 --> 00:01:26,931
So let's do input and let's just say,

19
00:01:26,931 --> 00:01:31,269
What would you like to do?

20
00:01:31,269 --> 00:01:35,380
And that space, okay, don't worry,
we'll capture it in a second.

21
00:01:35,380 --> 00:01:38,920
But let's come down here to the bottom.

22
00:01:38,920 --> 00:01:41,300
And let's call our menu function.

23
00:01:42,540 --> 00:01:46,663
And let's give it a look in the console.

24
00:01:46,663 --> 00:01:49,853
python3 app.py, cool, and

25
00:01:49,853 --> 00:01:55,507
you can see our input is
starting over here on the left.

26
00:01:55,507 --> 00:02:00,435
But all of this is getting our
indent that's coming from the indent

27
00:02:00,435 --> 00:02:02,996
here to be inside of our function.

28
00:02:02,996 --> 00:02:06,934
And inside of our while loop and
inside of our print function call.

29
00:02:06,934 --> 00:02:13,771
So to counteract that, I'm going to say,
let's start you on a new line with a \n.

30
00:02:13,771 --> 00:02:16,520
And then for the rest of these,
we'll do returns.

31
00:02:16,520 --> 00:02:19,320
It's like hitting the Return or
Enter key on your keyboard.

32
00:02:19,320 --> 00:02:23,291
So \ return, \return, \return,

33
00:02:23,291 --> 00:02:27,680
\return, \return, okay, save.

34
00:02:27,680 --> 00:02:34,670
And then to cancel this, we're gonna hit
Ctrl+C, and that'll cancel your program.

35
00:02:34,670 --> 00:02:36,673
I'm just gonna run clear.

36
00:02:36,673 --> 00:02:38,912
And then python3 app.py again.

37
00:02:41,485 --> 00:02:43,220
Cool, okay, that looks much better.

38
00:02:43,220 --> 00:02:45,050
It's over here on the left and
it looks nice and neat.

39
00:02:46,100 --> 00:02:50,120
I'm gonna go ahead and
hit Ctrl+C and clear it again.

40
00:02:50,120 --> 00:02:54,527
Okay, awesome, now we need to ask for
the user's input and

41
00:02:54,527 --> 00:02:56,920
we need to save it to a variable.

42
00:02:56,920 --> 00:03:00,820
So we have the ask,
let's save it to a variable called choice.

43
00:03:01,990 --> 00:03:06,777
And we also need to make sure that
the choice they give us is actually one of

44
00:03:06,777 --> 00:03:09,020
the available options.

45
00:03:09,020 --> 00:03:13,203
So let's do, if choice in, if it's in, and

46
00:03:13,203 --> 00:03:19,140
let's just do a list of our
options because it's quite short.

47
00:03:19,140 --> 00:03:23,604
So 1, 2, 3, 4, 5, so

48
00:03:23,604 --> 00:03:28,448
if it's one of these options,

49
00:03:28,448 --> 00:03:33,310
then we can return the choice.

50
00:03:35,070 --> 00:03:38,923
And if it's not, it'll just cause
the loop to go back up top and

51
00:03:38,923 --> 00:03:41,880
print out our programming books again.

52
00:03:41,880 --> 00:03:44,430
And it will try again.

53
00:03:45,530 --> 00:03:50,540
But to make it a little bit easier
on the user, let's also add an else.

54
00:03:52,260 --> 00:03:54,410
And then let's ask them to try again.

55
00:03:54,410 --> 00:03:57,220
That way they know that
they've made a mistake.

56
00:03:57,220 --> 00:04:02,354
So I'm gonna do, Please choose

57
00:04:02,354 --> 00:04:06,544
one of the options above.

58
00:04:06,544 --> 00:04:11,164
And I'm actually gonna make this
triple quotes here, one, two,

59
00:04:11,164 --> 00:04:14,230
three, let's go to the end, two, three.

60
00:04:15,240 --> 00:04:17,630
Okay, then I can do this.

61
00:04:17,630 --> 00:04:22,010
Please choose one of the options above.

62
00:04:22,010 --> 00:04:26,248
A number from 1-5.

63
00:04:28,381 --> 00:04:31,350
Press enter to try again.

64
00:04:31,350 --> 00:04:35,421
Okay, this way they receive some sort of
message before it kicks them back up to

65
00:04:35,421 --> 00:04:37,190
the start of the loop.

66
00:04:37,190 --> 00:04:40,550
Otherwise, they might think they
entered something correctly,

67
00:04:40,550 --> 00:04:41,993
had a little keyboard flub.

68
00:04:41,993 --> 00:04:45,078
And they thought they pushed 1 and
really pushed the key next to 1,

69
00:04:45,078 --> 00:04:46,333
that little tilde symbol.

70
00:04:46,333 --> 00:04:50,050
And instead of just seeing
the menu again and being like,

71
00:04:50,050 --> 00:04:52,070
wow, your program is broken.

72
00:04:52,070 --> 00:04:54,373
They'll get a nice little error
message and realize, oops,

73
00:04:54,373 --> 00:04:57,700
they must have typed something
incorrectly and they can try again.

74
00:04:57,700 --> 00:04:59,470
Okay, so
let's test this out in the console.

75
00:05:01,430 --> 00:05:02,450
So what would you like to do?

76
00:05:02,450 --> 00:05:03,600
Let's try just a letter, t.

77
00:05:04,720 --> 00:05:06,192
Please choose one of the options above.

78
00:05:06,192 --> 00:05:09,700
And you can see it's
getting this spacing again.

79
00:05:09,700 --> 00:05:13,710
So I'm gonna do, I'm gonna try doing \r.

80
00:05:16,317 --> 00:05:18,960
Save that, okay, but we can still test.

81
00:05:18,960 --> 00:05:23,616
Let's just try doing 14,
a number that's not in our range, and

82
00:05:23,616 --> 00:05:26,610
we still get the error, perfect.

83
00:05:26,610 --> 00:05:29,684
If we do one of the correct numbers,
it should return a choice,

84
00:05:29,684 --> 00:05:31,140
which we're not capturing.

85
00:05:31,140 --> 00:05:35,190
So it should just end our function,
perfect.

86
00:05:35,190 --> 00:05:36,240
That's the way it's supposed to work.

87
00:05:36,240 --> 00:05:39,960
And I'm gonna run it one more time just
to make sure that error is aligned

88
00:05:39,960 --> 00:05:40,740
a bit nicer.

89
00:05:40,740 --> 00:05:43,720
So I'm just do the letter t, there we go.

90
00:05:43,720 --> 00:05:45,306
Okay, that's nicely aligned over there.

91
00:05:45,306 --> 00:05:50,980
Cool, keyboard interrupt, clear.

92
00:05:50,980 --> 00:05:54,080
And our menu function's good to go.

93
00:05:54,080 --> 00:05:58,433
And it's important to note, the reason
why I'm using while True here is because

94
00:05:58,433 --> 00:06:02,570
no matter what, this function will
only end when this choice is returned.

95
00:06:02,570 --> 00:06:07,050
And return will always cancel out or
stop a loop.

96
00:06:07,050 --> 00:06:08,740
So that's why I used while True.

97
00:06:10,100 --> 00:06:12,240
Next, let's create our app function.

98
00:06:13,480 --> 00:06:17,140
Scroll down here to the bottom because
it's probably going to use a lot of

99
00:06:17,140 --> 00:06:19,380
the functions we're gonna be creating.

100
00:06:19,380 --> 00:06:24,267
And so this function will need to go at
the end right here before the dunder main.

101
00:06:24,267 --> 00:06:28,112
Add a couple spaces, and def app.

102
00:06:29,833 --> 00:06:33,257
Inside of our function, we'll need
a while loop to control our app,

103
00:06:33,257 --> 00:06:36,310
kind of like what we did
with the menu up above.

104
00:06:36,310 --> 00:06:40,092
So that when the file is run, the loop
will continue to let the user interact

105
00:06:40,092 --> 00:06:42,810
with the database until they
decide they wanna exit.

106
00:06:43,810 --> 00:06:48,260
Let's create a variable called
app_running and set it equal to True.

107
00:06:49,580 --> 00:06:57,830
And then let's do while app_running,
perfect.

108
00:06:57,830 --> 00:07:00,936
The first thing we want our users
to see is that main menu so

109
00:07:00,936 --> 00:07:03,200
that they know what options they have.

110
00:07:03,200 --> 00:07:05,260
So we can call the menu.

111
00:07:05,260 --> 00:07:11,750
And remember the menu, let me scroll up,
is going to return their choice.

112
00:07:11,750 --> 00:07:16,485
So we wanna capture that by
setting menu equal to a variable.

113
00:07:16,485 --> 00:07:20,360
And we can just call it choice so
that it's still their menu choice.

114
00:07:22,570 --> 00:07:26,420
Now that we have it, we can use if
statements to control what happens next.

115
00:07:26,420 --> 00:07:32,857
So if choice is equal to 1 then
that means from our menu above.

116
00:07:32,857 --> 00:07:38,418
And I'll scroll again, so
you all can see, we have 1 is Add book.

117
00:07:40,676 --> 00:07:44,970
So I'm gonna do 1 and I'm gonna do
a little note here, this is add book.

118
00:07:44,970 --> 00:07:50,026
And I'm just gonna put pass inside for

119
00:07:50,026 --> 00:07:56,193
right now cuz we'll add
all this stuff later.

120
00:07:56,193 --> 00:08:03,188
And then elif choice equals 2,
this was view books, pass.

121
00:08:03,188 --> 00:08:07,927
Elif choice equals 3 and

122
00:08:07,927 --> 00:08:14,410
then this was search for book.

123
00:08:14,410 --> 00:08:15,580
You need to put in pass.

124
00:08:16,700 --> 00:08:22,913
And then we need elif choice equals 4 and

125
00:08:22,913 --> 00:08:29,140
this is the book analysis, pass.

126
00:08:29,140 --> 00:08:33,206
And here we can just use else because
our menu function is already taking

127
00:08:33,206 --> 00:08:36,210
care of any other numbers
besides one through five.

128
00:08:36,210 --> 00:08:39,653
So we know we're only gonna get
numbers one through five or,

129
00:08:39,653 --> 00:08:42,680
I guess, string numbers one through five.

130
00:08:42,680 --> 00:08:45,979
So we can just use else and

131
00:08:45,979 --> 00:08:51,810
then we can put GOODBYE, Print, GOODBYE.

132
00:08:51,810 --> 00:08:58,090
And then we can set app_running
equal to False to turn off our loop.

133
00:08:59,110 --> 00:09:02,530
Now inside of dunder main, let me save.

134
00:09:02,530 --> 00:09:04,320
We don't need to call menu anymore.

135
00:09:04,320 --> 00:09:05,830
Instead, we can just call our app.

136
00:09:06,910 --> 00:09:07,921
Let's run the file.

137
00:09:10,330 --> 00:09:13,600
And awesome,
our menu's getting printed out still.

138
00:09:13,600 --> 00:09:17,370
And now we can test out
all of our menu options.

139
00:09:17,370 --> 00:09:20,540
So if I type in a letter,
I should still get an error.

140
00:09:21,660 --> 00:09:24,060
Awesome, I get the menu again.

141
00:09:24,060 --> 00:09:30,610
If I type in 12, that's not an option,
still get the error, perfect.

142
00:09:30,610 --> 00:09:36,285
If I type in 1, because we have nothing
in any of these choices, except for

143
00:09:36,285 --> 00:09:42,410
our Exit choice, it should just cause
the while loop to start back up the top.

144
00:09:42,410 --> 00:09:46,382
So if I do 1 I still get the menu,
2, 3, 4, and

145
00:09:46,382 --> 00:09:49,900
now when I hit 5,
it should close this out.

146
00:09:51,520 --> 00:09:54,600
And there we go, perfect,
it's all working great.