Name: CS50 2016 - 第9週 - SQL (CS50 2016 - Week 9 - SQL)
Uploaded: 2021-01-14T07:09:36.000Z
Duration: 1 h 51 min 48 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

You'll recall that last time, we took a look back at such things as Scratch.

Because recall that when we introduced Scratch,

we introduced a whole number of programming

constructs-- loops and conditions and functions and variables and more.

And then just one week later did we transition from that world of Scratch

to C, where the syntax was much more cryptic looking, certainly

at first glance, and perhaps a little bit still.

And now in week nine as we transition from the world of C to Python,

you'll find that that same finding is the case, whereby

But we have to translate it now to a slightly different domain

But things really start to get interesting this week

and beyond, especially as we build on our ability

to write Python code, our ability to serve up web applications.

Because now we can begin to leverage so much more functionality

than comes with C, than comes with the CS50 library,

because there's such a large community of software developers

who have created some really amazing things that we can try out.

So let's look further today at Python, and let's look further

at the applications for a language like this.

You'll recall that perhaps the simplest program we could have written last time

was actually just one line-- print Hello World.

But you'll recall as you began to dive into some of this past week's

challenges, you might have needed or wanted

to actually start wrapping code like that in a method or function like main,

and then calling it by default with this magical incantation here.

But this was the building block toward which we were starting

But now we're going to really context switch from a command line environment

And the world has been writing web-based applications for quite some time.

Even I 20 years ago recall made that Frosh IMs-- freshman intramural sports

And even since then have the languages changed and the paradigms changed,

and we humans have learned a lot about programming for web-based applications.

And this, for instance, is one design pattern or one architecture

that has arisen, whereby MVC refers again

to this pattern, whereby you put your intelligence, your so-called business

This is one or more files that has all the conditions,

a lot of the functionality calls, and actually does something

Then you have the views, which are often templates or files that

render information that you might have dynamically generated

And today, we start to dwell on the M in MVC, model, because last week,

we didn't really leverage much, if any, of a model.

But this week we're finally going to demand of ourselves the ability

to save data, retrieve data, search data, delete data, and more.

And we really haven't had this capability, other than very simple CSV

files, for instance back in the day of C,

and even last week when we dabbled with those in Python.

And you'll recall, last time we introduced this.

Flask is what's called a micro framework.

So a bunch of files, a bunch of code that a community of people

have written that just make it easier to make web-based applications.

In fact, one of the sample programs among last week's distribution code

if you like to go back and play was a program called serve.py

It just uses built-in Python functionality.

But you'll find that it's pretty cryptic.

It's pretty heavyweight in order just to do something simple.

And so things like Flask have come around that just make it easy

and dare say more pleasurable to write web-based applications,

because people have realized in writing web app after web app after web app

that they're just repeating themselves, or borrowing code

And so in frameworks, you have solutions typically to very common problems.

So we'll use this set of solutions to the development

And for instance, the simplest Flask application

that's also available from last week's source code

might be something like this, whereby the top of your file,

you don't import like the CS50 library, you instead import someone else's

library, specifically from the Flask framework import-- what's

called the class, recall, called Flask-- capital F.

And then also a function or method called Render Template.

Last week, we instantiated a Flask-based application

by essentially passing in this special reference

to the current file, the name of the current file,

and then allowing the framework to do its thing

and give us back this very special, very powerful object called app--

though we could have called it anything-- that gives us

For instance, the most useful functionality

And this is just syntax for what's called a decorator, and more

and that some other time, or more on that in Flask's own documentation.

But essentially, this line here-- @app.route,

says that hey server, any time you see an HTTP request for slash, the default

web page typically of a website, go ahead and call the following function

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CS50 2016 - 第9週 - SQL (CS50 2016 - Week 9 - SQL)

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