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Hello.

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And welcome to Python for Informatics.

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Right now we're going to cover Chapter
One.

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I'm Charles Severance from the University
of Michigan.

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And I'm the author.

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And I'll be your lecturer, for this online
lecture of the first chapter of the book.

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This lecture and my slides, and the book,
as a matter of fact, are all open.

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Open content, open materials.

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They're copyright Creative Commons
Attribution.

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And this video recording is also
copyright Creative Commons Attribution.

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It's important to be explicit about
copyright, and

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so I say it right at the beginning.

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So, computers basically want to be
helpful.

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They are programmed.

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[SOUND] Matter of fact, this is a
microprocessor.

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This is really just an electrical part.

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It's got wires and circuits inside of it.

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And somebody spent a lot of engineering
time, to make it so that these pins in the

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back take instructions from us, from
operating systems,

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from the hard drive, from the memory.

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Instructions come into here and then
results come out.

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It's really sort of a very programmable
hand

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calculator and it's our job to put
instructions in.

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This thing, in a sense, is wired to

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be curious about what's next, right?
It's like

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It, it's, like, tell me what you want to
do next.

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What do you want to do next?

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What do you want to do next, and after
that, what do you want to do next,

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and it just happens to do that a
billion or so times a second.

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And, so that's sort of the, the low-level
piece, and, but you can also think, if

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you have, like, a PDA, something like
this,

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all the buttons on here are some kind of,

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you know, "what's next?"

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Right?

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Each of those is sort of something begging

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for my attention, some application
developer who's built a

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really cool application and says please
use me, please

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click me, I am sort of nothing without
you.

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We humans are the things that sort of
cause computers to start doing

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something and this will sit here happily
until I caused it to do something.

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Now, [SOUND] whoa!

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Whoa.

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Hope it's still okay.

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Yeah, it seems to be fine.

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Seems to be fine.

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Takes a lickin', and keeps on tickin'.

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So, these, anyone can use, right?

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They say even animals can use a Macintosh,
smartphone.

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And so you don't have to be a programmer.

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But to get this to do what you want

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you need to learn a different language,
and we need to

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learn the language of the instructions to
tell it what to do.

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So, that's what we're going to do.

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We're going to learn how to talk to this.

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Yo!

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because it's asking us a question, we have
to give the answer.

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So, what's a programmer?

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A programmer is somebody who

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writes a program, which is a script or a
set of instructions that tell

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one of these kinds of things what it is
that they're supposed to do.

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And sometimes you're running a program
like Moodle, an open source

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learning management system, or Sakai,

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another open source learning management
system.

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And sometimes you'll even get paid to do
that, right?

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Sometimes you do it for free, sometimes
you

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get paid, sometimes you write things for
yourself.

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And and but, if you think about it, all
these

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applications on my iPhone, somebody's
making some money off of these.

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They may not be able to quit their job,
but a surprising number

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have been able to quit their job or
start

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small companies, maybe not gigantic
companies, but small companies.

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So these people that can put
applications inside of our computers

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are programmers, because they understand
the way that we talk to these computers.

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And part of what I'm going to try to do is
to get you to move from

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the mindset of the end user who thinks of
this as something just to click on

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to the mindset of the programmer, who's
kind of

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on the inside trying to get out to you.

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So that's, as we sort of move from user to

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programmer, we move from outside to inside
and we think

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of the world out there and it's like what
are

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they going to put, push, what button are
they going to push.

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So here's kind of a picture of that.

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So on the outside, we're users, we click
on buttons, we click

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on websites, we click on buttons on our
phones, et cetera, et cetera.

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But what's really going on inside all of
that is there's a computer with

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a bunch of hardware inside of that, and it
has inside of it data,

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networks, other information. And software
is what makes all that make sense.

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And so, part of what I want you to do is
I want you to stop

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thinking about how to use these things
from

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the outside, and we move to becoming a
programmer.

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We're someone on the inside.

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We're with the CPU, we are with the
memory.

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We are with the network connection.

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We are doing things on behalf of the user,
and presenting them back up to the user.

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So, why be a programmer?

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Now, this class is specifically not trying
to turn you

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into a professional programmer, even
though I'd be very proud

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if after five, ten more classes you were a

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professional programmer. But that's not the
purpose of this class.

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Sometimes you just want to get something
done.

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You got an Excel spreadsheet at work and
the data's not right.

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You got the data from somebody else and
it's

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got like extra spaces where it shouldn't
have it or

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does missing fields or something, you gotta do
something to it that Excel can't do.

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And you're, you're stuck, like, saying,
Aw, I

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want to, I want to mess with this data and

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put it in Excel so I can do my job, but
it's a pain in the neck.

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And I have to sit and bring it into a text
editor like Microsoft Word

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and go line by line and make all kinds of
mistakes and clean the data up.

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You can write a program to do that,

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and that's the kind of programs we're
going to do.

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Programs that serve our needs inside the
computer, but to serve our needs.

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Professional programmers tend to build
things for other people to use, right?

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They, they tend to build things that
everyone else does.

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But we're going to build stuff primarily
for ourselves.

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So.

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What is code?

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What is software?

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We use these words pretty much
independently, a program.

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It's really a sequence of stored
instructions.

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We learn the language that this talks, and
then

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we will feed the instructions in, one at a
time.

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It takes them one at a time, it gives us
back a result, we give it the next one.

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It gives it back, in, out, in, out.

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So it's really a sequence of stored
instructions.

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But it's kind of more than that.

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It's, it's sort of like our creativity,
and if you've been using some of

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my software, like my MOOC software, I

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spent about a month writing all that
stuff.

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And it's like, it's me.

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I mean I'm, it's my vision of how cool
stuff ought to work, right?

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And so it's more than just getting
something done.

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It's also a sense of pride and a sense of
accomplishment.

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Especially if you're giving something that
other people can make use of.

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It's really, I think it's very creative.

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And it's what attracted me to being a
programmer in the first place.

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It's that I could, I could leverage the
abilities inside of here,

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and I could do things, cool things, on
behalf of the user.

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So, code, software, a program.

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So, let's get a non-technical example of
this.

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So, I'll have you link out to the YouTube
[COUGH] for this.

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This is the Macarena.

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The Macarena is a song that

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has with it a well-known dance that
everyone

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seems to know, or either get taught very
quickly.

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So I'll, I'll stop and let you watch the
Macarena, and then come back.

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[BLANK_AUDIO]

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So welcome back.

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I hope you enjoyed that.

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In a sense what we've got there is

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a program.

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A program for human beings.

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And, maybe you learned that at a club or

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something, and they told you what to do
next.

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Well, I can teach you how to do

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the Macarena by writing a simple program
right now.

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So here's my Macarena.

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While the music plays, means you do it
over and over

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and over again, to the beat, that's kind
of like computers.

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They do things in a beat.

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They happen to have three billion beats a
second.

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But as it were, so we're going to do this
multiple times so

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we have this whole group of instructions
that we're going to do, right?

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Left hand out and up, right hand out and
up, flip left hand, flip right hand, left

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hand to right shoulder, right hand to left
shoulder, et cetera, et cetera.

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Now this particular little program has a
mistake in it.

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Actually several.

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I want you to look and see if you can find
the mistakes in the program.

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[BLANK_AUDIO]

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Okay.

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So here are the places that have the
mistake.

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Right?

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The mistake is

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right ham to the back of the head, and
left hand to right hit, not hip.

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Now if you're in a bar and you take a ham
and you hit somebody

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in the back of the head, that's not very
nice when you're dancing to this song.

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These are what's called bugs.

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Now a human reading this

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would say, oh, I think they meant to say
"hand" here.

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But a computer is much more literal than
people.

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We'll see a couple of exercises where
we'll see that people

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can correct little mistakes like this, but
computers they cannot, right?

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So we have to fix these bugs and we have
to say

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right hand and we have to say hip when we
mean hip.

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So we have to be explicit.

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Computers do exactly what we say.

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They don't do what we mean to do.

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So, let's clear that.

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Here is another example, okay?

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Let's see how this comes out.

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[SOUND]

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[MUSIC]

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You're supposed to count the number of

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times the word "the" appears in this
sentence.

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Count it.

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And the word "the", how many times?

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[MUSIC]

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Okay, it's your turn.

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[BLANK_AUDIO]

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Now, here.

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[BLANK_AUDIO]

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This is not something humans are good at.

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I moved it around, I played a little
music, I confused you,

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I put a picture of a clown car in the
upper left-hand corner.

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Et cetera, et cetera, et cetera.

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Now it turns out that computers, once we
tell

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them what to do, are very good at
concentration.

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It can easily go through 30 words and find
the most common word.

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Or three million words and find the most
common word.

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And it'll never make a mistake.

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We first have to give it a set of
instructions.

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So, I don't want you to learn this right
now, but this is a Python program.

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Let's say that I want to teach, let you
count words in files, okay?

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I say hey, I know how to program Python,
I'll

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send you an email, and I'll send you this
program.

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Just stick it into Python, and it will
count words for you.

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Right?

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You've got a million words, million
lines in a

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file, you want to find the most common
word.

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And so, so here we go.

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So I will send you this file called
words.py

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I spent a little time, it's a friendly gift
to you.

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And this is what I type in. Now I'll give

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you kind of an outline on what this is
going to do.

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First thing it's going to do is open a

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file and read it, then it's going to
split

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the lines and files into words based on
the spaces.

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Then it's going to run through and
accumulate

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numbers like, you know, this word is one,

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this word is one, oh I saw that again so I
turn that to two.

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That's what this does, it's a loop, it
goes

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round and round and round, one for each
word.

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Then what we're going to do is
we're

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going to write another loop that's going
to figure out

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which is the most common word by looking

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at all those little histograms that we
built up.

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00:11:45,450 --> 00:11:47,590
And then it's going to print those things
out at the very end.

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And this can certainly do Python words.py
and read clown.txt

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00:11:53,570 --> 00:11:56,730
and tell us that the word "the" occurs seven
times.

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00:11:56,730 --> 00:12:00,290
But, you know, it can go, it can find out
that a different thing

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00:12:00,290 --> 00:12:04,220
has the word "to" and that it occurs sixteen
times and it's just as fast.

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So yeah, you have to learn a language and
you have to tell it what to

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do, but once you do it'll do it for a
million or a billion words and happily.

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So you don't have to do menial work

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00:12:14,510 --> 00:12:19,585
once you understand the way to
instruct the computer to do menial work.

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[NOISE]