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Setting Up Our App
9:56Import the CSV of books to create your first entries.
With our database ready to go, we need
to start building out our application.
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Let's start with the menu function.
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It'll print out the menu options
to the console, ask the user for
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their choice, and then return their
choice for use in our main app function.
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Couple spaces.
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def menu and then inside we're
going to create a while loop.
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Do while True.
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And then let's print out our menu options.
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Print, two, three, four, five, six, and
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I'm doing the triple so
that we can do multi-line here.
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And let's do, I'm gonna do caps lock,
PROGRAMMING BOOKS.
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1 is going to be Add book.
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2 is going to be View all books.
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3, Search for book.
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4, Book analysis,
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and 5, Exit.
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Great, and let's do the input, too.
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So let's do input and let's just say,
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What would you like to do?
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And that space, okay, don't worry,
we'll capture it in a second.
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But let's come down here to the bottom.
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And let's call our menu function.
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And let's give it a look in the console.
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python3 app.py, cool, and
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you can see our input is
starting over here on the left.
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But all of this is getting our
indent that's coming from the indent
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here to be inside of our function.
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And inside of our while loop and
inside of our print function call.
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So to counteract that, I'm going to say,
let's start you on a new line with a \n.
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And then for the rest of these,
we'll do returns.
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It's like hitting the Return or
Enter key on your keyboard.
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So \ return, \return, \return,
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\return, \return, okay, save.
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And then to cancel this, we're gonna hit
Ctrl+C, and that'll cancel your program.
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I'm just gonna run clear.
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And then python3 app.py again.
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Cool, okay, that looks much better.
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It's over here on the left and
it looks nice and neat.
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I'm gonna go ahead and
hit Ctrl+C and clear it again.
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Okay, awesome, now we need to ask for
the user's input and
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we need to save it to a variable.
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So we have the ask,
let's save it to a variable called choice.
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And we also need to make sure that
the choice they give us is actually one of
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the available options.
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So let's do, if choice in, if it's in, and
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let's just do a list of our
options because it's quite short.
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So 1, 2, 3, 4, 5, so
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if it's one of these options,
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then we can return the choice.
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And if it's not, it'll just cause
the loop to go back up top and
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print out our programming books again.
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And it will try again.
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But to make it a little bit easier
on the user, let's also add an else.
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And then let's ask them to try again.
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That way they know that
they've made a mistake.
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So I'm gonna do, Please choose
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one of the options above.
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And I'm actually gonna make this
triple quotes here, one, two,
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three, let's go to the end, two, three.
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Okay, then I can do this.
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Please choose one of the options above.
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A number from 1-5.
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Press enter to try again.
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Okay, this way they receive some sort of
message before it kicks them back up to
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the start of the loop.
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Otherwise, they might think they
entered something correctly,
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had a little keyboard flub.
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And they thought they pushed 1 and
really pushed the key next to 1,
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that little tilde symbol.
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And instead of just seeing
the menu again and being like,
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wow, your program is broken.
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They'll get a nice little error
message and realize, oops,
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they must have typed something
incorrectly and they can try again.
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Okay, so
let's test this out in the console.
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So what would you like to do?
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Let's try just a letter, t.
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Please choose one of the options above.
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And you can see it's
getting this spacing again.
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So I'm gonna do, I'm gonna try doing \r.
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Save that, okay, but we can still test.
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Let's just try doing 14,
a number that's not in our range, and
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we still get the error, perfect.
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If we do one of the correct numbers,
it should return a choice,
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which we're not capturing.
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So it should just end our function,
perfect.
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That's the way it's supposed to work.
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And I'm gonna run it one more time just
to make sure that error is aligned
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a bit nicer.
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So I'm just do the letter t, there we go.
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Okay, that's nicely aligned over there.
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Cool, keyboard interrupt, clear.
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And our menu function's good to go.
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And it's important to note, the reason
why I'm using while True here is because
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no matter what, this function will
only end when this choice is returned.
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And return will always cancel out or
stop a loop.
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So that's why I used while True.
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Next, let's create our app function.
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Scroll down here to the bottom because
it's probably going to use a lot of
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the functions we're gonna be creating.
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And so this function will need to go at
the end right here before the dunder main.
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Add a couple spaces, and def app.
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Inside of our function, we'll need
a while loop to control our app,
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kind of like what we did
with the menu up above.
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So that when the file is run, the loop
will continue to let the user interact
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with the database until they
decide they wanna exit.
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Let's create a variable called
app_running and set it equal to True.
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And then let's do while app_running,
perfect.
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The first thing we want our users
to see is that main menu so
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that they know what options they have.
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So we can call the menu.
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And remember the menu, let me scroll up,
is going to return their choice.
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So we wanna capture that by
setting menu equal to a variable.
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And we can just call it choice so
that it's still their menu choice.
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Now that we have it, we can use if
statements to control what happens next.
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So if choice is equal to 1 then
that means from our menu above.
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And I'll scroll again, so
you all can see, we have 1 is Add book.
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So I'm gonna do 1 and I'm gonna do
a little note here, this is add book.
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And I'm just gonna put pass inside for
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right now cuz we'll add
all this stuff later.
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And then elif choice equals 2,
this was view books, pass.
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Elif choice equals 3 and
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then this was search for book.
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You need to put in pass.
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And then we need elif choice equals 4 and
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this is the book analysis, pass.
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And here we can just use else because
our menu function is already taking
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care of any other numbers
besides one through five.
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So we know we're only gonna get
numbers one through five or,
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I guess, string numbers one through five.
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So we can just use else and
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then we can put GOODBYE, Print, GOODBYE.
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And then we can set app_running
equal to False to turn off our loop.
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Now inside of dunder main, let me save.
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We don't need to call menu anymore.
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Instead, we can just call our app.
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Let's run the file.
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And awesome,
our menu's getting printed out still.
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And now we can test out
all of our menu options.
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So if I type in a letter,
I should still get an error.
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Awesome, I get the menu again.
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If I type in 12, that's not an option,
still get the error, perfect.
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If I type in 1, because we have nothing
in any of these choices, except for
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our Exit choice, it should just cause
the while loop to start back up the top.
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So if I do 1 I still get the menu,
2, 3, 4, and
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now when I hit 5,
it should close this out.
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And there we go, perfect,
it's all working great.
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