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In an earlier video on if statements,
we created a very simple guessing game.

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The player had to guess a number
between 1 and 10. We want to open up

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that guessinggame.py file and work
on that in this video. Now what I'm

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going to do is delete the commented out
code at the end, because we no longer

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need that. Alright so there's our code at
the moment. Now as it stands there's a

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number of problems with this game.
One problem is that it only allows two

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guesses. If we wanted to allow more than
two guesses, we'd have to nest more and

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more if tests every time the player
guessed incorrectly. The other problem is

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that five is always the correct number,
which makes the game a bit boring,

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and not that it was terribly engaging to
begin with. Now the first problem can be

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solved using a while loop, which is what
you'll be doing in the challenge coming

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up next. Before we do that, though, let's
digress slightly and address the second

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problem, so that we can produce a more
interesting game. To fix the problem of

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the correct number always being five, we
need to get the computer to generate a

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random number in the chosen range - that's
one to ten in the example - but we can

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extend that. Python has a lot of features
built in such as the ability to do

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arithmetic, lists, ranges and tuples and
more. There's enough built in, in fact, for

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us to be able to write a random number
generator if we wanted to do that.

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The good news is though, however, one has been
written for us and comes included

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with Python in a module called random.
We'll be looking at creating modules and

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packages much later in the course, but
for now what we're going to do is use

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the one, the random generator, that comes
with Python. Because it's in an external

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module, we need to import it into our
program to use it, using an import

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statement. When you want to use objects
from the Python standard library you

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import them, usually at the start of your
program. Importing a module allows you to

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use all the objects from that module in
your own code. So we want to use the rand

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int function from the random module, so
we can start by importing random. We're

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going to do that right up on line one, by
typing import random. Now that we've

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imported the module we can use its rand
int function on line three. So let's

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change the five, the literal value
five to random dot randint parentheses

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1 comma 10. I've used random.randint
on line 3 because the randint function

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is in the random module. We imported
random on line 1 at the start of the

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program and we can now use the functions
it contains by using what's called dot

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notation. We separate the module name
from the function name with a period or

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dot, which is why it's called dot
notation. We're using dot notation to

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tell Python that the randint function
is found in the random module.

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The randint function produces a random
number within the range we specify.

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We've passed the values 1 to 10 to the
function, which means we'll get a random

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number from 1 to 10 inclusive. So we've
used the value 10 in two places in our code.

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If we wanted to increase the range
of numbers that the player has to guess,

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we'd have to make a change in both of
these places. That's a good way to

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introduce bugs in your code, so if we
changed the value on line 3 but forgot to

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change the message on line 5, the program
wouldn't behave as the player would

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expect it to. We can make the code more
robust by using a variable to store the

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upper value, so let's have a go at doing
that. So on line 3 I'm going to type

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highest is equal to 10.
Then on line four I'm going to change the

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literal value 10 to highest, like so, and
then what we're going to do is change

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our message here, delete 10 and put
left and right curly braces instead,

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and after the double quote put .format and
in parentheses, highest. Now we can increase

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the range if we wanted to by making a
single change on line three and a change

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would be reflected in both places.
Alright so let's run the program and see

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if we can guess the number. So I'm going
to guess five the first time, and if

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that's too low I'm going to guess eight,
otherwise I'm going to guess three,

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unless five happens to be correct of
course. So let's try five and I got it first

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time, amazing! It is actually quite hard
to test this program properly, unless

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we're really lucky. We can't test that it
prints the right message when we guess

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correctly, but of course I got it correctly
the first time, so let's try running it again.

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I'll try five again, Please get higher.

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This time I'm going to guess 8, as I
mentioned I would do, and it was too low,

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and well done I guessed it. Well I'm having
an amazing amount of lucky here because this

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is entirely random.
We'll try one more time.

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We'll try five again and that's just,
again, amazing. Three times out of three.

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Please guess higher. We'll try eight
again. This time finally, we've got it wrong.

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Sorry you have not guessed
correctly and I'll try one more time just to

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see if we can get the opposite to happen,
five again, Please guess lower this time.

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I'm going to try three, Well done, you
guessed it. Again I'm having an amazing run

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of luck here. One more time - I can't believe
I've got this right so many times but we'll try

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one more time, Please guess higher.
I'll try eight and we'll leave it at

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that. So we didn't get to see us not
guessing it correctly by guessing a lower

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one, but that's fine.
That really alludes to the fact that it

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is quite hard to test the program
properly, because even if it does print

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the message we can't tell if it should
because we've got no idea of what the

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correct answer is. So to get around that
while testing, what we can do is print

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the value of answer out. So for testing
purposes, it just makes it easier for us

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to know rather than just guessing, so
what I'm going to do is add the code

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on line five. I'm going to do print answer,
and that's gonna be the answer

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from the, so that's basically the number
that's been randomly generated. I'm also

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going to put a comment here, hash TODO
remove after testing. Obviously you wouldn't

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want to leave this in, in a real
game, because of course what would happen

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would be the player would know the
number to guess each time. Now you might be

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wondering what happened with that TODO.
Two things; firstly, it changed to blue

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when I typed TODO, but secondly, IntelliJ
treats comments that start with TODO in

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a special way. It highlights them in blue
with my color scheme and also keeps

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track of them. Down at the bottom of the screen
we've got a TODO tab. I'm gonna come

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down here and click on that. If we open that
up we can see that it'll give us a list

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of all the TODOs, in this case, just in
the one file we've got, and it actually

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tells us there that on line five, we've
got print answer and it shows us the

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TODO that I've actually entered. So you
can basically expand the sections and

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double click on a particular entry to go
straight to that line in your code, so

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for example, if I was down there, double
click it, my cursor moves back up the

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line five - very useful if you happen to
be in another file at the time. So in

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general, TODOs are a great way to keep
track of things so that you don't forget

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about changes you intended to make. Note
that this is a feature of IntelliJ, the

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IDE. It's not a Python feature. Python
just treats that comment like any other.

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Alright, so at this point now, the program
should be easy to test, even though I had

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a good run of luck last time. I'll just
close down the TODO tab. Let's run it again,

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and what I can do is check what happens

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if I get the correct result first time,
and on my second guess. So the first time,

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we know that the value is one there.
So we enter 1, we got it first time so

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we know that that's working. We'll
try it again,

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this time I'll enter a number that I
know is too high,

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8, Please guess lower. Well I could
guess 5, guessing the number correctly

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on the second time, Well done you've guessed
it. And obviously, now that you know the

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number, you could go through all the different
scenarios of testing, to make sure you

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fully test all program flow conditions.
So at this point, you'll probably find

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the program a bit frustrating. With ten
numbers to choose from we'd probably

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need a minimum of four guesses, to be
sure of getting the number if you didn't

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know the answer in advance, and that
sounds like a good challenge to try.

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So the challenge is to modify the

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program to use a while loop, to allow the
player to keep guessing. The program

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should let the player know whether to
guess higher or lower, and should print a

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message when the guess is correct.
Now it already does that, but I suggest

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you don't worry about printing a
different message, if they get the

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correct answer on their first guess.
We'll look at counting the number of

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guesses later. A correct guess will
terminate the program. Now as an

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optional extra, allow the player to quit
by entering 0 for their guess. So these

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challenges are intended to give you a
chance to practice what you've learned.

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Don't think of them as tests. There's no
pass or fail as such. If you have a go but

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don't manage to solve the entire
challenge, or even part of it, that's fine.

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Generally, most people, even if they don't
successfully complete it, will learn

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something from the experience, so it's
well worth giving it a go. The bottom

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line is, you'll learn a lot more by
trying before you watch my solution

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coming up in the next video, than you
would if I just presented you with the

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working code. So have a go and see how
you go with it, and we'll go over that

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solution together in the next video.