#100DaysOfCode in Python Transcripts
Chapter: Days 19-21: Iteration with itertools
Lecture: Concepts: what did we learn?
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Well, I hope you really enjoyed itertools,
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because it's really one of our favorite modules.
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It's just so much fun to use, and saves you so much time.
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So, without further ado, what did we cover?
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The first thing we covered was itertools.cycle.
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Okay, so itertools.cycle,
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we just imported cycle from itertools.
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Go figure.
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Then, we specified the iterable.
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Okay, the iterable that we wanted cycle to go over, okay?
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and for our little exercise there,
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it was those weird dashes,
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so that we can make a little scroller.
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If you were to use a string, such as the word string
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or my name, Julian,
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it would then cycle through those letters
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in the same way that it's cycling through those.
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Okay?
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And that's why cycle is so easy to use.
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It does exactly what its name implies.
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It's awesome.
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Then, what we did was we threw it in a while loop,
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while True, so that it was infinite,
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it would just keep running while this app was live.
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And then we pumped that..
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Next, we pumped that cycle out to standard out.
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That way it would work well on the command line.
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Okay?
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Using Next, we were able to actually go through
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one iterable at a time.
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One iteration at a time.
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Okay, so we know each iteration, each cycle
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is going to be one of these characters here.
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So, Next got us to pull just that one in the first loop.
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Then, in the Next loop, it then took the backslash,
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and then the pipe, and then the forward slash.
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Okay?
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That's how this works here.
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And then we just threw in a little time.sleep,
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just to slow things down a bit.
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Next we have itertools.product.
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So again, we imported product, okay?
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And then what we did was we used repeat, okay?
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We used the repeat inside product to say
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how many combinations we wanted.
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How many times we wanted a single iterable
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to be repeated or any iteration to be repeated.
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Okay?
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So by specifying two, when we iterate over my name,
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we were able to start getting a giant list just like this.
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Okay?
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So J matched with J, J and then U, and so on and so forth.
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Okay?
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And that's what product is, it's a Cartesian product,
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it gives you every possible combination.
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Okay?
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It doesn't matter in this instance with the doubles,
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where you've got J and J.
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There's no sort of behind the scenes
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differing index there to say,
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"Hey this is one J, and this is another one.
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"So there needs to be double."
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No.
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It's just a J, okay?
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Then we moved on to combinations and permutations,
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one of my favorites.
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Imported, nice and easy.
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And then we created a quick list of super friends,
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Mike, Bob, and Julian.
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And this was for us to then use as an example.
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So we got the combinations, okay?
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In sets of two...
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Of Mike, Bob, and Julian.
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And you can see we have Mike Bob,
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Mike Julian, and Bob and Julian.
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And then that's when we pointed out
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that, well, there's no order here.
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It takes it into account that, okay
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Mike and Bob both exist in this one tuple
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and therefore that's criteria met,
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that's a combination.
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But, if we wanted the order to change,
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if we wanted to take that into account,
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that's where permutations comes into it.
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We have Mike and Bob here,
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but then we also have Bob and Mike over here.
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So the order actually makes a difference.
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And that's why permutations is
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just as awesome as combinations.
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And that was it.
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So your turn.
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If you haven't yet, I would strongly recommend,
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go and do the traffic lights, okay?
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Try not to watch the video until you've actually done it.
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But at this point, you've probably already completed that.
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So that was for day two.
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So we're looking at the third day of this lesson set.
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For this, go back to the three day overview,
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if you've forgotten what it is that we were talking about,
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but essentially there are a few bites
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to go to the Code Challenges Platform,
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and you have free access to those
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and all three of them have to do with itertools,
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and they're actually quite fun.
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So if you haven't done that,
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go and give that a crack for day three.
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Enjoy.
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Keep calm and code.
