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Comparisons
10:56You can compare objects. Let's explore how.
So we just picked up the ability to
check out the equality between objects,
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the double equal sign right?
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So let's explore some more
comparison operations.
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Let's explore these in the shell first,
so we'll say python.
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Now to check and
see if values are not equal,
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we use the exclamation mark and
then equal sign, right?
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So that exclamation mark there
is sometimes called bang,
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you'll hear people say bang.
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So bang equals is not equals.
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So, hot-dogs are not equal to sandwiches.
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True, now unfortunately that's
not solving the age old debate.
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It's just saying that
the strings aren't the same.
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And speaking of an age old debate,
my daughters are 6 and 3.
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You can use the greater than
symbol to compare numbers, so
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6 greater than 3, true.
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And this confirms much of to
the disappointment to my little one,
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that my eldest is indeed older.
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She's greater in age.
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And just to double check we can
do the reverse, is 6 less than 3?
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I'm sorry sweetie.
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So, there will be cases where you'll
want to check if a value is equal to or
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greater than another.
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So you can combine that with
a pretty handy operator,
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you can say, is 42 >= 42?
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And as you can see it compares
each of these operands.
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That's what these values are on both
sides, they're called operands, and this,
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they're being operated
on by this operator.
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It says are they greater than or
equal to each other?
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Now, real quick,
you can do this with strings as well.
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So we could say,
is sunshine greater than rain?
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Which is obviously true, but
that's not why it's returning true.
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This is doing alphabetical order,
s comes after r, it's greater than r.
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So here's how I want to use our new
comparison operators in our program.
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So, what happened was, I showed
this program to my six year old and
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she put in her name and the program
suggested that she start learning Python.
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Which, I obviously totally agree with, but
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she should really learn to read
a little bit better before diving in.
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So, let's do this.
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Assuming first name is an r name or
r fellow student's name,
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we should ask for their age.
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So if it's less than or
equal to, let's say six,
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let's suggest that they learn to
read first and then learn Python.
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So we can do that, right?
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Now, it might not be
completely clear to you, but
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it's totally fine to nest an if statement.
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So let's do that, let's come in here
inside of our else here, right?
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So it's not us, it's not here so,
we don't know who they are.
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So let's go ahead and
say age equals input, how old are you?
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And we'll give some space, and
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now remember that input
always returns a string.
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But we actually need here what we need is
an integer, cuz we're gonna compare to it.
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So, let's coerce what is returned
into an integer and you can do this,
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we can do this by wrapping it.
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We can say int, and then on this other int
here, we can do this, so what's happening
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is we're coercing whatever is returned
from here, which is gonna be a string.
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So we're gonna take the string and
put it into here.
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That make sense?
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So we only want to do this if they
are less than or equal to six.
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So if age is <= 6,
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I'm gonna start my body.
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And we'll say print.
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Wow, you're like five, four, three,
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two [LAUGH] if you're confident
with your reading already.
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And then we'll just go ahead and
say what we were gonna say.
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We gotta format this, we'll push in
the age and that'll automatically happen.
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I'm gonna make sure that
I'm balanced there, okay?
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Great, and so what's gonna happen,
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they will only see this message if they're
less than 6, less than or equal to 6, and
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then it will print and you
should totally learn Python.
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Cool, so let's go ahead,
let's make sure that we save this.
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I'm gonna come in here,
drop out of the console.
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And I will clear and
will say python hello.py.
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So run this with my daughter, her name was
Hattie and hello, Hattie, how old are you?
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So awesome, we're in the else,
we've got a new input here.
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We'll put in 6, which will be a string,
I'll turn it into an int.
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It says wow, you're 6, if you're
confident with your reading already,
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you should totally learn Python,
Hattie, awesome.
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Now if you read this
script from the very top,
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it should be pretty clear
to you what's going on.
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Well, I mean especially
since we wrote it together.
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But, there's a little bit of logic
here that is particular to a use
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case that I just introduced.
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It might be a little confusing as
to why we are asking for age here.
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So there is a concept called comments, and
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what you can do is you can
put in a sentence here.
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So let's do that.
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So to create a comment, you just put in
a pound sign, also known as a hashtag,
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depending on your age.
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And then we just put our comment.
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So we can say, this is just in case we
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have a younger user who can't yet read.
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And comments are great.
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And at this point in your learning
journey, feel free to put them everywhere.
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A lot of students like to take notes for
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the different parts of the program
to write in the comments.
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And that's totally fine.
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You'll see as this language becomes second
nature that you'll probably need fewer
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comments.
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Now comments are great for
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reasoning what might not be
clear to readers of your code.
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However, if you're needing to explain
what a line of code is doing,
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you might want to think about
rewriting that line of code, or
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breaking it down until it's
more easy to understand.
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Writing readable code is a skill
that improves over time and
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we'll build up your skill set together.
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One of the most wonderful things about
Python in particular is how easily
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the language can be read.
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Now part of this readable comes from
the required indentation of the language.
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This code will not work if I
remove some of the indentation.
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So watch this I'll go ahead and
I'll take a little bit of this age off.
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And right away, see how it turned red?
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It's like, stop.
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So I'm gonna go ahead and
save this even though that's red.
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And let's run it and see what happens.
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And you'll see that the error's
actually on line nine, and not line 10.
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And it's saying that there's
an indentation error.
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So what I want you to remember, is to
remember to look around when that happens.
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It's saying 10 but
the error is actually on line nine.
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Let's clear this up.
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Phew, that feels better already.
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Speaking of reading code, what do you
say we read through this one more time.
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So we came in here with Hattie,
and first name now equals Hattie.
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And we say, hello Hattie?
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And then we check to see if first
name is equal to your name,
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it's Craig here in my code.
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And since it doesn't,
we drop down to the next else if.
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And it say is equal to
our student Maximiliane.
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It doesn't, so therefore,
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since none of these if statements
turned out, we run into our final else.
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And that's here, and we ask input
from our user of how old they are.
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And this comment directly above
shows us why we might be doing that.
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The input function
always returns a string.
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And we need to coerce that to an integer,
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because we want to compare
that in our next line here.
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We wanna say, are you less than 6?
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Less than or equal to 6.
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And because of my experience,
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7 is really about the time that you
don't need to focus too much on reading.
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So much growth happens at five and six,
but I don't think you're quite there yet
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reading level wise.
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So this definitely could read less than
seven, which is essentially, less than or
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equal to six, right?
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Now, if that expression was true,
we print out this message.
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And when we call the format string,
we're passing in an integer but
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it's automatically coerced
back into a string for us.
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And, of course, that only happens
if the age is less than or equal to 6.
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Then everybody is
suggested to learn Python.
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And then, finally, have a great day.
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So how'd that feel?
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Did that all make sense?
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Now if it didn't,
let me remind you that you can rewind me.
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Just scrub your video player
back a minute or so, and
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you can walk that code all again.
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Now if it wasn't all crystal clear,
remember, that is totally fine.
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This very well could be your
first time looking at code.
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Think about how much of it
you actually did understand.
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And then try to compare it to what
you knew before we met each other
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way back when in that first video.
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It's kind of a lot of new stuff, isn't it?
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Great job immersing yourself,
stick with it.
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You got this.
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If you have questions please ask them.
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Every one is super nice in the community,
and chances are someone might be having
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the same question that you're having,and
they just haven't asked it yet.
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Check the questions
attached to this video.
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Can you help somebody?
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I want to reiterate that you're
doing great learning the basics.
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Taking input and
then branching to display different output
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based on various conditions is
how most applications work.
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Think about how most websites,
that require you to sign in,
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actually work behind the scenes.
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Now if you aren't logged in, it shows
you the buttons to Login or Sign Up.
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If you click the Login button, the form
shows up, and you input your username and
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password.
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Now, in the case that you are logged in,
it shows your profile picture, but
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you don't see the buttons.
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Think about what that
code might look like.
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If the user is logged in,
we display the user's avatar.
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Otherwise, we need to show the buttons.
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Now that display profile avatar is
a function that we would need to write.
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And we'll get to that in a bit, but
see the branching logic at play.
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See how the output is using a boolean
variable to determine which branch
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should work.
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Also, that login input,
that's just taking input, right?
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Just like our command prompt.
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It returns what the website user entered,
so
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that the values can be
used to log the user in.
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You just learned a bunch of concepts.
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You've got the building blocks that are
present in all sorts of applications that
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you use today.
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I bet you'll start looking at your apps
a little bit differently as you start to
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use them.
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I am excited for what's coming up next.
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We're gonna take a look at
writing our own functions and
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how to use loops to repeat your code.
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I can't wait to get those functions and
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loops added to your ever
growing bag of tricks.
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Let's do this.
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