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[VIDEO PLAYBACK]

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DAVID MALAN: --the equivalent C version.

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So guess what else we
can do with Python?

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Not only can we re-implement all of
weeks one through five's examples from

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C in Python, so can we
implement the entirety--

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[END PLAYBACK]

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DOUG LLOYD: That was his.

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So, much like a number of the staff,
I actually had not extensively

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programmed in Python myself.

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And so I was actually
sitting in the audience

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when this lecture was being filmed.

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I don't remember you doing this at
this time in the lecture, though.

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DAVID MALAN: Sometimes entire
blocks of material slip my mind,

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and we realize after
shooting a two-hour lecture,

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oh shoot, forgot an additional example.

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And this one has actually
been important, I think,

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so this is the example in which we
translate problem set five in CS50

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from C to Python, the
spell checking problem set.

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And the whole point, and we've
done this for years in PHP as well,

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is to demonstrate just
how much more quickly

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and with how many
fewer lines of code you

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can implement the exact
same functionality

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in a higher-level language
like PHP or Python

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and to show also the
price you pay, typically,

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in performance because of the
overhead of interpreting the source

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code in Python.

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DOUG LLOYD: Right, because
it's not pre-compiled

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so you have to deal with that step.

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DAVID MALAN: Indeed, now
we're not-- yeah, exactly,

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not manually compiled as students
might have with Clang, for instance,

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in the world of C. So, yes,
this is a bit of movie magic.

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We might have shot this after the
lecture wrapped and then went back in,

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and our team kindly
sliced it in earlier.

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And no one would know this--

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DOUG LLOYD: --but for the fact
that this is CS50 explained,

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and we have a chance to talk about it.

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DAVID MALAN: Thanks for explaining that.