#100DaysOfCode in Python Transcripts
Chapter: Days 37-39: Using CSV data
Lecture: Demo: Answer the questions
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Alright we're ready to answer the questions,
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let's go through this again.
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I'm going to move this down just so it fits right here,
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so we initialize the data.
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Boom, we're doing that.
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The next thing we need to do is say
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research dot let's say hot days.
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Now what we're going to do is we're going to write a function here
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that is going to give us all the days, hottest to coldest.
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And we come over here and say days equals this,
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then we could loop over and say for d in days,
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and that would show all of them.
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But we want just the top five, and so the way you do that
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in Python is using something called slicing.
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So you can come over here,
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and say I would like to go from index 0 to index 5.
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Alright so this gives us a little subset of our thing,
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and when it starts at zero or ends at the length
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you can just omit it.
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So we can write it like this,
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and that will process the first five of em'.
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And then let's just say, print d for a second.
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So we're going print out what that looks like.
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So let's go write this hot days function.
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Alright so we want to go through our data,
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and figure out the hot days.
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And it turns out, the easiest way to do this
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is just to sort it.
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So we can say return sorted data.
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Now that's going to sort it by, jeez I don't know, maybe the
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first element, alphabetical, by date, I'm not really sure.
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So we want to control what it's sorted by,
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and in here we can say there's a function
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that is going to take basically one of these items,
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one of these rows,
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and tell us what we're going to use to sort for it.
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So we're going to say key equals lambda
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this is a little in line function.
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Lambda says there's a function,
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then the next thing we put is the argument.
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So let's say r for record,
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we do a colon and then we have the body of the function,
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the implementation.
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Where do we want to sort by for hot days?
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Let's say with a max temperature for the hot days.
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Actual max temp is what we want.
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So we're going over here and I'll say r.actual_max_temp.
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Now this is close,
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this is going to actually give us the lowest value first,
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and then the highest value to the end.
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So the default sort is going to go from low to high,
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how do you reverse it?
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There's two ways, we could say reversed=True,
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I'll spell it correctly, that's one way,
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or another way a little more flexible,
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is to just put a negation here and say
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multiply that by a negative number.
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So take your pick, you can do it either way.
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While we're here let's write the cold days function,
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that should be easy.
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On the cold days take away that.
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And let's do wet days.
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And this time we're not going to sort by that,
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we're going to sort by actual precipitation.
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And again wet days are where we have more,
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so we want to sort that in reverse.
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Now the format is a little off so reformat the code.
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So PEP 8 is happy.
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Alright so those three functions actually
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should do what we need.
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So let's go over here and we'll just print out the five hottest days.
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Now this is probably not how we want to view it,
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so let's print this out slightly differently.
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So I would actually like the index,
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like this is the number 1 hot day,
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this is number 3 hot day, so I can come over
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and say idx, and instead of just looping over the days,
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I can innumerate them and then loop over.
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And that will give us the index and the day, for each time.
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So then in here we'll put something like a little dot to
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say what day it is and we'll say the temperature in terms of
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Fahrenheit on such and such day.
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And we'll just do a little string format on this.
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So what this is idx and it's zero base, you don't talk in
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terms of 0 1 2, you talk in 1 2 3 so plus 1.
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And then we need the day, dot.
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Now notice we're not getting any help here,
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let's go back to these real quick.
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So we can come over here and tell Python this is a record.
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Now if we do that,
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sorry not a record, you can tell it it's a list of record.
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Now this is a Python 3.5 feature,
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and if we come over here we import this typing.List.
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So at the very top, we have from typing import List,
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and we put this here, and I'll go ahead and while we're here
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just put it on the others because they're all the same type.
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We come over here and now we go back to this,
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and I say let's try that again, d.
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Oh yeah, now our editor is smart, now it can help us.
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What we want here, we want the actual max temperature,
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and then we want d.date.
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Alright, let's go and run it,
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see if this whole thing's hanging together.
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Boom, look at that, hottest five days, 96-94-92-91-90.
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And those are your dates, that's awesome, right?
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See how easy it is to answer the question.
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The challenge was not actually answering that question,
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the challenge was taking the data, reading it in,
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and then converting it to a workable format
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and storing it in our record.
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Once it's stored like that it is easy.
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Let's go ahead and do the same thing for the coldest days.
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So we'll say that days is not the hot ones but now it's
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research.cold_days, should do exactly the thing.
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And let's do a little print in between just so there's some
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spacing, and you guessed it,
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the wet days, same thing, just ask for the wet days.
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Let's run it, so there's our hot days,
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the cold days look really cold,
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well doesn't look that cold does it?
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Did I get the cold?
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That might be the high on the cold days.
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Let's go down here yeah.
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Yeah, yeah, careful.
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This going to be actual min temp,
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like so, and this is going to be actual precipitation.
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There we go.
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Let's say, inches of rain,
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there we go.
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Oh yeah, now that's starting to look cold isn't it.
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23 Fahrenheit, that's like negative negative 5 Celsius
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for those of you who are on the Celsius scale,
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this is like 36-37.
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Alright so pretty hot, pretty cold.
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I notice the sorting is correct.
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The weather stays, the heaviest amount of rain
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during that time was 2.2 inches, or 5 centimeters.
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And then it goes down pretty quickly from there.
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So hopefully you really got a good sense of how to take the
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CSV file in, read it, parse it,
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convert it to a usable format
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and then just quickly answer questions.
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We stored it in a list and sorted the list, there might be
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other data structures you need to use for your data.
