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Python 3, an illustrated tour Transcripts

Chapter: Classes and inheritance

Lecture: Walk-through: Matrix Multiplication

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In this video, we're going to look at the mul test assignment

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and there's a function test mul that says

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implement a class vector that accepts a list of numbers

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implement the matrix multiplication operator

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to return the dot product multiplying each corresponding value, then sum the results.

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Okay, let's do that.

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Let's make a class, it's going to be called vector

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and let's implement a constructor here

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and it's going to take data, vector has input

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and we'll just attach that as a member and let's implement matmul guy.

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Okay, it's going to take another vector presumably

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so what we can do is we can loop over the pairs of data together

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how we do that is we can use the zip function.

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So the zip function takes two sequences

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and it will loop over both of them until one exhausts.

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So we're going to have self.data and other.data

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we're going to need something probably result is equal to 0.

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And we're going to zip those together so I can say this and that in zip

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res plus equals this, times that, return res.

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Let's see if this works.

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Okay, that looks like it did work.

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We can do a little bit of refactoring if we want to here,

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we can put this into a list comprehension

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and so we could do something like this

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we could say well we're going to accumulate this, this is a sum operation,

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so we're going to say sum of the iterable

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what we're going to sum is what we're accumulating which is this

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and we'll take this for loop and we'll plop it into here

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we'll take off the colon at the end

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and we should be able to say res is equal to that.

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Let's run this and see if it works.

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Okay, it looks like we're good.