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SPEAKER 1: This is see
as CS50 Finance, where

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we'll make a website that allows users
to sign up, register, log in, and buy

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and sell stocks or shares
that they're interested in.

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Well, first, there's going to
be a lot of distribution code

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for us to read over.

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There are Python files, HTML files,
and even one database file, .db.

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And we have to understand
how all of those

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interact with one
another and the functions

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that we've provided that will make
this problem a lot easier to handle.

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Then, once we read
through all of that, we'll

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implement register, where users
can sign up for the website.

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Then, we'll implement
quote, which allows

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users to look up the price for a stock.

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Buy allows them to buy a certain
number of shares of that stock.

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Then we'll edit the
landing page and index,

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such that logged in users can see
their transaction history as well

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as some other information about
the cash that they have on hand

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and the total value of their holdings.

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We'll of course allow them to
sell any shares that they have

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and view the history
of those transactions.

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Finally, you'll have
the freedom to implement

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an additional feature of your choosing.

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Now, this may seem like a lot of to-dos.

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And I'm also going to add some
subtasks under each category.

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So it might be a little
overwhelming, but as always, we're

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going to take this bit by bit and
break it down into manageable bites.

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First, let's open application.py.

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You'll notice at the very top,
we have a lot of dependencies.

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We import a lot of packages and modules.

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This will allow us easier functionality
as we progress through this problem.

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Feel free to check out the documentation
for all of these dependencies.

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Then we ensure that
responses aren't cached.

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This means that whenever we
make a request from the server,

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it actually fetches from the server
as opposed to going into the cache.

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So we get fresh data every time.

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Then we configure the Flask session
and configure the CS50 library

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to use the SQLite database.

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Then you'll notice that
we have login required

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before every definition of these pages.

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That means that the user must be logged
in order to access the given route.

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More on login required later on.

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As we continue through
application.py, we'll

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notice that login and logout
are both implemented for us.

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So these are going to be important
to understand how they work

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but also to use as a
framework to understand how

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we might implement the other routes.

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Also notice how we call the
apology function and the database

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execute function.

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Some other things to
take note of, whenever

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we have a form submission via post,
we can retrieve it as follows.

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In our HTML template within the
templates folder, if we have our HTML

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and we've specify the name of our
input box, then within Python,

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we can then request that
via request.form.get

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and then specify the name
of that input in order

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to retrieve the variable that
was submitted from the form.

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Note that the execute
function for the SQL database

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always will return an array.

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So that means that even though I
only selected one specific cash

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value for one specific user,
in order to access that value,

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I'll have to access the very
first row of the array rows

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and then go to the index of
cash in order to get that value.

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Feel free to take some time and read
through application.py so you really

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understand how it's working.

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For now, I'm going to
move on to helpers.py,

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where we'll see the implementation
for apology and login required.

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We'll also see the lockup function,
which is going to be useful.

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Lookup allows us to take a
stock symbol and then returns

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the name, price, and symbol of that
stock encapsulated within a dict.

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It does this using Yahoo
Finance, which allows us

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to fetch stock information via a URL.

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Then we have usd, which nicely
formats the prices for us.

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Now we can move on to
the templates directory.

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There are only three files in
here, apology, layout, and login,

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all HTML files.

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So take a look at these
and figure out how

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they interact with their respective
routes with an application.py.

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And surely, you'll be
adding additional templates

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as you progress through this problem.

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Finally, we have the
requirements.txt and then

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the CCS style sheet which you can
feel free to edit as you see fit.

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Once you're comfy with the distribution
code, and I mean really comfy,

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then we can start implementing register.

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