Name: CS50 2017 - Lecture 9 - Python, continued
Uploaded: 2017-11-14T16:52:42.000Z
Duration: 1 h 19 min 37 s
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DAVID MALAN: All right, this is CS50, and this is lecture 9.

And so we've been diving into bunches of languages

recently among them have been HTML, and CSS, and Python most recently.

And soon we're going to see JavaScript soon.

So let's see just a moment if we can kind of wrap our minds around what's

So HTML, which we looked at a couple of weeks back, is used for what?

OK, good, so marking up a website, the structure of the website,

and the contents of the website are what you would annotate using HTML--

It's not a programming language, so it doesn't

have functions, and loops, and conditions,

and the kind of logical control that we've used for some time.

It really is about presenting information.

CSS, meanwhile, allows you to really take things the final mile

and really get the aesthetics just right.

And so, in fact, what I just described, boldfacing, and italics, and centering,

early on in version 1 say of HTML was actually how you did it.

But these days, the better approach is to factor out those kinds of aesthetics

from your HTML and instead put them in this other language, CSS, Cascading

So your HTML now becomes put this text in a column.

And structure your data in a certain way.

And then stylize it with colors, and fonts, and placement using CSS.

Now meanwhile, most recently, we introduced Python.

DAVID MALAN: More straightforward syntax, yeah, in some ways,

and we'll see some syntax where you take that back, I think.

But in general, that is kind of the case,

because you don't need parentheses if they're not strictly necessary.

You don't need curly braces just because.

Instead, things like indentation become more important, which on the one hand

is a little annoying, but on the other hand,

And then at the very end of the last lecture,

we did something that was hopefully wonderfully inspiring,

And so we've really, we pretty much re-implemented

all of problem set 5 speller using like I don't know, 15, 20, 25 lines of code,

not to mention I was able to type it out within 30 seconds.

And that's not just because I knew what I wanted to type,

but really because you have to write so few lines of code.

With Python, and soon with JavaScript, and even other languages out there,

you just get so much more functionality for free.

If you want to know the length of the string, you call a function.

If you want to get a linked list, you create a data structure called a List.

If you want a hash table, you create a data structure called a Dictionary.

Underneath the hood, someone else out there in the world

has implemented all of that functionality for us.

But now we're standing on their shoulders.

And so today, what we begin to do is to transition

to this last portion of the class, where our domain is not just a command line

and dot slash something, but web programming, where the ideas are pretty

much going to be the same so long as we now understand, as hopefully you

do or are beginning to, what HTTP is and how the web and the internet

So recall that we looked a little bit ago at a URL like this.

And so if you were to visit https://www.facebook.com and hit

Enter in your browser, you're going to send some kind of message

in an envelope that might physically in our world look like this.

And what is inside of that envelope, if you simply

do type that URL before trying to get to Facebook?

AUDIENCE: An error message that redirects to--

DAVID MALAN: Yeah, probably no error message here, because that URL

And it wouldn't so much be an error message,

but like a preference to go to a different location.

Not moved, only if we had gone to a shorter URL.

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CS50 2017 - Lecture 9 - Python, continued

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