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ZAMYLA CHAN: It's me, Zamyla.

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Today we're going to
recreate the Mario problem.

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One of our very first problems in C,
now we're going to make it in Python.

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So if you recall from
your Mario problem,

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then you'll remember that what we
had to do was to prompt the user

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and validate their input,
and then draw pyramid.

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To prompt the user in C,
CS50 provided our own library

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in which we had the function get_int.

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So in order to use this
get_int function you

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had to hashtag include the CS50 library.

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In Python we also provide
you with the CS50 module

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with the exact same function get_int.

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But instead of hashtag including
it, we're going to import it.

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That's the equivalent in Python.

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In order to ensure that
we got proper user input,

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we typically used a do-while loop in
which the do-while loop would ensure

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that we prompted the user at least once,
and then we would only repeat that loop

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if the user gave us invalid input.

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Now Python actually doesn't
have a do-while loop structure,

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but Python does have an
equivalent while loop.

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So let's see how we can
take a while loop in Python

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and turn it into the
correct functionality,

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mirroring the do-while loop.

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Here, as my condition for
the while loop, I have true.

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So that means that the loop
will execute at least once.

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So I'm going to prompt the user there
and then, if a certain condition

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is met, I'll break out of the loop.

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But if that condition isn't met,
then that loop will repeat itself.

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Another difference
between C and Python is

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how we express the compound
conditional expressions.

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For ors and ands, we used
two characters, but in Python

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we simply just need to type
those words out, "Or" and "And."

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Notice also in red I've indicated
some of the syntactical differences

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between C and Python.

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So here I show how you need to
include a colon after your condition

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in order to enter that if condition.

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Remember also that style is
quite literally Python syntax

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and how it interprets the code.

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So, if before you used to do your
style after you wrote all of your code,

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that won't do in Python.

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So make sure to indent correctly in
order for all of your code to execute.

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Now that we've prompted and
validated the user input,

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the next thing that we have
to do is to draw the pyramid.

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Now the logic hasn't changed so
the pseudocode also hasn't changed.

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For every row we'll want to print
the left pyramid, spaces first, then

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hashes, print the gap, two spaces,
and then print the right pyramid.

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Printing just the hashes without any
trailing spaces, those aren't needed.

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You'll notice that the
pseudocode is exactly the same.

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No logic has changed for this problem.

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So the only rule that
changes is the syntax.

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So how do we print in Python?

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Well printing in Python comes
by default with a new line.

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So if I simply included
"Hello, world" in the string,

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then it would print a
new line after that.

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So if I want to override this, then
I'd include a comma after the string,

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and then indicate end equals
with two empty quotation marks.

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Now if I wanted to print
something, say 50 times,

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then I would include a star
50 right after the string,

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and there I would have
50 hashes printed out.

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Finally to just print a new
line, I would call print,

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and I just wouldn't pass anything
in, and I'd have any new line.

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So there we have our Mario pyramid.

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My name is Zamyla, and this was Mario.

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