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Here's how I did it!
So, did those problems take a while?
0:00
I feel like the while-loop is a bit of
a simpler concept than the for-loop,
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probably because it's just a condition
with no variable or iteration needed.
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Let's look at how I solve these problems.
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The first problem, heating the oven
is a pretty normal use case for
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a while-loop, so
we'll say while current_oven_temp < 350.
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So as long as it's under 350,
we can go ahead and increase it, right,
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so current_oven_temp + = 25, and
then print current_oven_temp.
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Now, you could do these in either
order depending on how you read
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the instructions.
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Maybe you feel like you should
print it before you increase it or
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increase it before you print it.
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It really doesn't matter though and
if it's not less than 350,
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so this would be where else comes in, then
we want to print out, the oven is ready.
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Now, we could do this
without using the else, but
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I like to include them as it makes it
a bit more obvious what's going on.
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So let's go ahead and test this one,
so we'll do python while.py.
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And we can see we've got 100, 125,
150 and so on, until we get to 350 and
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then the oven is ready.
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Great, so it looks like we're getting
all those intermediate degrees.
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Onto problem number two.
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Okay, so the first thing that I have
to do is have an infinite loop.
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So I'm gonna go ahead and do while true,
which is a loop that will never end.
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You could also do say while one,
or while a, or
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anything that's always
going to evaluate as true.
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So then I'm gonna ask for a number.
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Now, I'm gonna go ahead and I'm gonna
lowercase it, which, of course, won't have
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any effect on the numbers, but it makes
the queue comparison a little easier.
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So I'm gonna say, num = input.
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And i'm gonna say,
give me a number or q to quit,
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and then I'm going to call lower on that.
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All right, so
now let's do that comparison.
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So if num == 'q' then break.
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Now, I'm gonna use break here to
immediately end the while-loop.
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Now, like I said,
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you could do this without the break,
but I like to have the break in there.
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Okay, so now,
let's try to turn it into a number,
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to be a bit more flexible,
I'm just gonna turn them all into floats.
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But you could make whatever decision you
want here, if you wanna make them ints,
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floats, whatever, as appropriate.
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So I'm gonna do,
try: numbers.append(float(num)),
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the float version of the num.
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And then the exception that I'm
going to catch is, ValueError.
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And if the ValueError comes up,
then I'm gonna do, continue, so
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I'm just gonna start that loop over again,
okay?
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So if anybody gives me something
that's not a number and it's not q,
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then we're just gonna ignore it.
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We're gonna pretend it didn't even happen
and we're just gonna go on to the next
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step of the loop, which comes right
back to the input, all right.
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Now, I could leave out the continue,
I could put in, say, pass instead.
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They're effectively the same in this case,
but
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continue is like the more obvious thing.
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Okay, so now,
we're done with the loop's code.
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Because at this point they have either,
they've even wanna put in a new number, or
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they've give us a q and they wanna quit.
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So, I can't use the else here that I
would normally have used, because this
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break counts as the loop ending early and
so, that makes it skip the else clause.
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So I'm just going to do the code
that I wanted to do here.
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So I'm gonna print out you entered, That,
and then the numbers that they entered,
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and then I will print out the total is,
and then the sum of the numbers.
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And sum, if you haven't heard
of this function before.
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We'll take a list of numbers, and
it will add them all together,
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and then I will print, the average is, and
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then we will print
sum(numbers)/len(numbers).
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And all right, so now that should do it.
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So this is gonna call
total_and_average for us, so
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let's go ahead and python while.py.
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Give a number, okay.
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So, let's do 5, 5, 5, and 5,
and then let's do a queue.
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So we entered 5, 5, 5, and 5.
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The total is 20 and
the average of that is 5, cool.
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So that's handy I guess, depending on your
needs for calculating averages and sums.
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Okay, so now, let's try problem number 3,
this is our last problem.
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Now, this one needs us to skip over
numbers that aren't evenly divisible by
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three or five.
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Now, initially, I was thinking that
I'd want to use continue on this, but
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there's really no reason to.
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Much like problem number one,
we need a condition in our loop.
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So we're gonna say while current > 101.
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Then we'll check the division,
or divisibility of the number.
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Now to do this,
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I'm going use the modulo operator,
which returns the remainder from division.
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So, if not, current % 3, or
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current % 5 == 0, then print(current).
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So you probably don't wanna
do this exactly like me.
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I'm showing you deliberately two
different ways of testing this right now.
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You pick which ever one's
more obvious to you.
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So first we have the not current % 3, and
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this one will evaluate the true
if the remainder is 0.
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Because 0 is falsy and the not swaps it.
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So instead of being falsy,
it becomes truthy because of the not,
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and then the current % 5 is equal to 0.
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It should be pretty obvious, but we're
comparing to see if when I do modulo of
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modulo 5 against current
if that comes out to 0.
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So if so, that becomes true.
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So if this is true or
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if this is true, if either one of them is
true then print out the current number.
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Now, finally,
we need to increment the number.
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So move up to the next number, and
that should do it, let's test that out.
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So python while.py, now,
I'm gonna get asked for a number.
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I'm gonna put in a 1 and q, and
then we get our numbers in here.
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So like 99 is divisible by three, 96 is
divisible by three, 100s divisible by 5,
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90s divisible by three.
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But we're not getting like say 82
which isn't divisible by 5 or 3.
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So awesome that's all of our numbers.
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Thanks for practicing loops with me.
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Hopefully, this will help you get
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more comfortable with these
super useful constructs.
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Be sure to let us know if any other
topics that you'd like to see a bit
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more practice on.
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