#100DaysOfCode in Python Transcripts
Chapter: Days 37-39: Using CSV data
Lecture: Demo: Parsing the CSV file
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We were able to read our file as text,
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and that gets us really close,
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but it doesn't really let us work with it.
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And now, technically, we could do,
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like a crazy bunch of string operations and parse this.
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But, it turns out it is entirely unnecessary.
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So we can import the csv module.
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This is a built in in Python.
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I'll call this reader, and I'll say csv.DictReader.
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There's a couple of kind if readers.
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DictReader is the best one.
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And you pass it this file stream.
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And what this thing is, is it is something that
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you can loop over, and every time you loop over it,
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you get the values out, okay.
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So, let's do just something really, really quick, and,
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just for row in reader, and just so
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you can see it working I'll print out, let's say.
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So if we run this,
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looks like it's working,
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and what we get is something called
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an Ordered Dictionary.
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Doesn't matter that it's ordered,
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all that matters to us I can ask it for
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the date, or the actual mean temperatures.
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Like, if just want to print out this part,
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I can go, because this is a dictionary,
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let's comment that out, I can just print here,
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row.get the actual mean temperature.
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Great, it looks like we already got a lot of data,
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and we could work with it.
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There's one super, super challenging problem, though.
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If I really want to work with this data,
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you very likely want to ask,
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is this thing less than that other thing, right.
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Is this temperature less than that?
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So we can answer our questions.
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What's the hottest day, what's the coldest day?
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Things like this.
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So, let's print out the type, right.
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This is going to tell us the actual underlying data type here.
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Strings, everything that comes back
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from CSV files are strings.
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Even if they look like dates, or they look like,
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you know, numbers or something.
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And so in order to actually work with these,
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we're going to have to do something a little bit different.
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So, we're going to actually write a function
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that takes this sort of raw row that we have here,
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and instead of just saying we're going to store the text,
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we're actually going to convert the numbers to numbers,
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the dates to dates, things like that.
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So we can actually answer questions like,
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is this number less than that number?
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Alright, the string less than or greater than
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is not the same thing
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as numerical less than or greater than, right?
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Like, 100 is less than 7, for example,
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if those were strings, but obviously not as number.
