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Add functionality to your app so the user can add books to the database and then view all books in the database.
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Welcome back, Pythonistas.
0:00
We've got our database created, the books
from our CSV file added to our database,
0:02
and our app's initial work all finished.
0:06
In this video, we'll tackle
adding books to the database and
0:10
viewing all of the books in our database.
Pop down into our app function.
0:14
If the user chooses 1,
they want to add a book.
0:23
They'll need to input a title,
0:26
an author,
0:34
a date,
0:43
but remember,
we need this date in a specific format.
0:52
And we have a handy dandy
clean_date function already.
0:56
So if we look at our CSV file, we need
the dates to come in something like this.
1:01
So I'm actually just gonna copy that and
put it in here as an example.
1:06
That way,
the users know what we're looking for.
1:11
Colon and a space, and
then let's also do price = input('Price').
1:15
And I'm gonna do the exact
same thing because we also
1:22
need price to match what we already
have going on in the database.
1:27
Now let's test this out
with some edge cases.
1:40
That one clear, there we go.
1:44
And we wanna do for
a terminal output here, there we go.
1:46
We wanna do 1.
1:51
So title, I'm just gonna use nonsense.
1:53
Author's nonsense, published date,
let's do February.
1:56
I have to do February in my brain
to spell it right, 31, 2004.
2:02
Okay, that date does not exist.
2:07
So what happens?
2:09
Well, it just kinda takes it.
2:11
So we're definitely gonna need
to clean and check for errors.
2:13
What happens if I do 5.99
with the dollar sign?
2:17
Well, it looks like it took that, too.
2:20
So we're gonna need to make sure to clean
both the published date and the price.
2:24
So let's use our functions
we've already put in place.
2:29
And I'm gonna say date.
2:35
I now want this variable to be equal to
clean_date, and I'm gonna pass in date.
2:36
So essentially, what I'm saying
is I'm gonna grab your input,
2:41
save it to this variable.
2:46
Then I'm gonna clean your input and
2:47
I'm gonna set the same variable
equal to now the clean information.
2:50
Because I don't need
the not clean information.
2:55
I need the clean one.
2:59
And do the same thing down here,
price = clean_price(price).
3:01
And if this is messing with your
brain a bit, you can change this to
3:08
date_clean and price_clean if
that helps your brain out a bit.
3:14
Let's save, and I need to do a keyboard
interrupt, and run the file again.
3:22
And let me do this so
we can see our terminal a bit better.
3:29
Okay, so let's do 1,
choose nonsense, nonsense.
3:32
And let's try February 31, 2004.
3:36
Okay, sweet, I get an error.
3:43
It says, the day is out of range for
that month, which is correct.
3:45
It should give me an error, but
it also crashes the program,
3:50
which I don't like so much.
3:53
So we're going to need
to handle some errors.
3:55
Let me clear the console.
4:00
Actually, I'm gonna leave it here just so
we can see that it's a value error.
4:02
So let me go up into clean_date, and
4:08
we need to turn on a try block.
4:12
Let's do try/except/else, and
4:15
this is gonna pop up
a try/except/else block for me.
4:18
It's kind of a fun little quick enter.
4:22
And inside of our try block,
I'm going to move all three of these.
4:25
Cuz as we know, if we put in something
other than the correct information,
4:29
like let's say I can test it right now.
4:34
Let's say 1.
4:37
Let's say I did 01-13-2003.
4:40
If I do something like that,
a totally wrong date format,
4:44
it's also going to give me an error.
4:47
So I'm gonna move all three of these
4:50
inside our try block, tab, tab.
4:54
And if I scroll up a bit here,
you can see the datetime also
4:59
caused an error when we did
that February 31st date.
5:04
So let's move datetime also
inside of our try block here,
5:09
and let's give it
a return_date variable name.
5:15
And then else,
we can return return_date, awesome.
5:21
Now we need to handle the error it's
giving us, which is a ValueError.
5:27
And inside here, we need to give the user
a clear message as to what they did
5:34
wrong and how to fix it.
5:38
So let's do an input so that it'll pause,
and one, two, three, four, five, six.
5:40
That way, we can do multiple lines.
5:46
I'm gonna do \new line, and
I'm gonna make this kind
5:49
of obvious that it's an error, DATE ERROR.
5:53
And let's say the date format
6:01
should include a valid Month,
6:07
Day, Year from the past.
6:15
And then let's do \r and
let's give them an example.
6:21
And let's do January 13,
6:27
2003, and \r and
6:32
press enter to try again.
6:35
And then just to close it out,
I'm gonna add some stars
6:40
here to kind of help sandwich
it between these two lines.
6:45
Okay, now, another thing I'm going
to do is I'm going to add return,
6:52
and I'm not gonna put anything after it.
6:58
This is the same as doing return none.
7:01
You just return and it also returns
none if there's nothing there.
7:03
That way, Oops, can get rid of that now.
7:07
It's a little extra little piece of code,
there we go.
7:14
Now let's come back down here, okay.
7:19
Now where they're going to input the date,
we can create a while block.
7:23
Let's do date_error = True and
while date_error.
7:28
And this way,
we can tab these two pieces in here and
7:33
they'll continuously be asked for
7:38
a date until they provide
us with the correct date.
7:42
And we can check that by checking
the type of our variable here.
7:47
If it's a datetime object,
then they've correctly given us a date.
7:54
== datetime.date.
8:00
And if it is,
then we can set date_error = False.
8:06
And we're gonna do essentially
exact same thing with our price.
8:11
So since we're already in here,
let's start in here.
8:21
price_error = True.
8:25
And while price_error.
8:31
And then we can tab these over, tab, tab.
8:34
And if type of price is an integer,
8:42
then we can say price_error = False.
8:50
Perfect, now we need to pop
up into clean_price and
8:58
do the same try except block.
9:02
Oops, I think I went too far, there we go.
9:06
Okay, I'm going to take our price_float.
9:13
I'm gonna cut it, paste it.
9:18
Need this to be a ValueError.
9:22
And we're gonna give them,
I'm gonna copy this one and just edit it.
9:29
Ctrl+C, Ctrl+V, and
9:35
instead of DATE ERROR,
this is PRICE ERROR.
9:38
And the price should be a number
9:44
without a currency symbol.
9:50
And example, 10.99.
9:58
And then instead of pass,
we want to return.
10:03
And the reason I'm not putting this
integer switch in there as well is because
10:09
if this float works,
then it's already a float number,
10:13
so converting it to an integer
should automatically work.
10:16
So we have our clean_price and
we have our clean_date,
10:21
and we are using them
inside of our app function.
10:26
So let's give them a try.
10:31
Scroll up here, and let's do 1,
it's nonsense, nonsense.
10:41
Okay, let's see, if we do 01-13-2003,
I should get an error.
10:49
Date error, press enter to try again.
10:54
Enter, and we get to try again.
10:58
Okay, let's try February 31, 2004.
10:59
It is an error, try again.
11:06
Let's try January 22,
11:07
2021, awesome.
11:13
Okay, now let's try and
see if we can break our price to 5.99.
11:18
So it didn't like that, okay.
11:22
If we say it's twenty five, it's an error.
11:28
If we say it's 5.99, and
it takes it, awesome.
11:33
So that's all working for us now.
11:39
The last thing we need to do is to
actually add the book to our database.
11:42
So at the end, if our if choice for
11:46
adding a book, make sure you tab back over
so that you're outside of the while loop.
11:51
We're going to put in new_book = Book.
12:01
And the title is going to equal
our title variable above.
12:07
And the author is going to equal
the author variable above.
12:11
And the published_date is
going to equal the date above.
12:18
And the price is going to equal the price.
12:25
Awesome, now we can add
session.add(new_book),
12:30
and we can call session.commit, wonderful.
12:37
Save and
let's check this out in the console.
12:43
Let's scroll down here, and
I'm also gonna turn this back on.
12:45
And we can also turn this back on.
12:51
And I'm gonna actually have that
happen before our app.py goes.
12:54
Cool, save, and let's give this a run.
13:01
Okay, Python app.pi.
13:08
Let's add a new book.
13:12
Let's call it Jethro's Favorites,
and the author is my dog Jethro.
13:14
And the published date, January 22, 2021.
13:20
Price is 5.99.
13:27
Okay, Enter, and great,
it looks like everything went well.
13:31
Now let's exit, and
it was added to our database, fantastic.
13:36
There's just one small thing.
13:42
I'm going to add one small effect
to our code to help the user know
13:45
the book was added.
13:50
After the commit,
let's print out that the book was added.
13:51
Then at the top of the file,
we're going to import something,
13:57
lots of scrolling, called time.
14:03
And scroll back down.
14:10
And we're gonna call time.sleep(1.5).
14:17
And this is going to pause our program for
one and
14:24
a half seconds before continuing on.
14:27
Feel free to pause me and
play around with it.
14:31
Now that we've added quite a bit of code,
let's add it, commit it, and
14:35
push the changes up to our repo.
14:39
Here we go.
15:01
Pushing your code up every so
often is an excellent habit to get into.
15:04
If something were to happen and
you lost your code,
15:09
you would still have it up in your repo.
15:12
Next on the list is being able to see
all of the books in our database.
15:15
Let's try to create something nice and
readable.
15:19
For book in session.query(Book).
15:25
And I'm gonna do print cuz we
wanna see them in the console,
15:32
and f string, and let's do book.id.
15:37
Space pipe space book.title space
15:44
pipe space and book.author.
15:49
And if you wanna put the published date
and the price in there as well, go for it.
15:54
I'm gonna leave it with just the title and
author for now.
15:58
Then at the end, I'm gonna do an input,
16:03
input new line press enter
to return to the main menu.
16:08
And this is just so the user can take as
much time as they want scrolling through
16:16
the books before they automatically
get sent to the main menu again.
16:20
They have a little bit of control here.
16:25
Okay, so
let's see this in action in the console.
16:27
There we go.
16:39
That's what I wanna run, Python app.pi.
16:40
Let's run number 2, and awesome.
16:43
We see we have 11 books in the database,
their ID, the title, and
16:46
the author, perfect.
16:51
If I press Enter, I'm set back to
the main menu, press 5 to exit.
16:53
And that loop is still turned on, so
we'll see all of our books printed out.
16:58
Amazing, another task complete.
17:03
So go ahead and do another,
git add, git commit.
17:05
Put in able to view books,
and then git push.
17:18
And there it is, nice work, Pythonistas.
17:29
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