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Instructor: Every time I go to the states,

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I always get very confused with what to wear,

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because I never know what the temperature actually is

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because I think in Celsius

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and it's really hard actually

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to get used to thinking in Fahrenheit,

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like what is cold, what is warm.

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So in this exercise,

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we're going to build a Python program to do that for us.

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We're going to take an input,

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which is already in the format of a dictionary,

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and each day has a temperature associated with it,

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a number in Celsius,

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and we're going to output, similarly,

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a dictionary where the keys are exactly the same.

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Monday, Tuesday, through to Sunday,

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however we're going to convert the values into Fahrenheit.

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In the description pane, you'll see the formula

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that is used to convert Celsius into Fahrenheit,

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and what you are gonna be doing is writing some code

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to do some dictionary comprehension,

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and take a dictionary and create a dictionary.

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If you take a look at the example input,

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and what the example output would look like,

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then you'll understand what our goal is.

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And if you take a look at line one,

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you'll see that we have this code called eval,

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which all it does is takes the input as a string

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and converts it into a dictionary.

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You can try running the code and printing out weather_c

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to see what that variable looks like as it is right now.

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But your goal is to write the code

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that takes the example input,

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dictionaries with Celsius values,

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converted into the example output,

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dictionary with Fahrenheit values.

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So have a go now.

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The first thing we do in our dictionary comprehension

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is to create the new variable, weather_f,

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and then set it equal to a new dictionary.

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What we're going to loop through

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is a list of weather items in Celsius.

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Now we're using the .items method that comes from Python,

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which takes our dictionary and outputs a list

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where each key and value pair is an item in the list.

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And if you print out weather_c.items as it is,

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you'll see that each key value pair

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is converted to what's known as a tuple.

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A tuple is something

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that is contained within a set of parentheses

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where the values in the tuple

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are associated with each other,

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but they can have different data types.

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So in our case,

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we've got a string and we've got a number

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that has been split out where each item

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is added into the list.

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The next part is to loop through each of those tuples.

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We're using our for loop,

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as standard in our dictionary comprehension,

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and we're defining what we are looping through

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and giving each of those parts

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of the tuple a name to work with.

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We're writing for parentheses,

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which is the structure of a tuple,

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the first part is day,

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which is our string that represents a day of the week,

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comma, and then the temperature,

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which is gonna represent the number

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that we're gonna work with later on.

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So now we have a for loop

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that loops through each of the items

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in our dictionary as a list,

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and we have a way to access the day of the week string

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and the temperature value.

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Now, all that's left to do

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is to structure each of the values

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in our new dictionary that we wanna output.

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The key value structure is simple.

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The key is going to be the day of the week,

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completely unaltered,

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and then we add the colon, and then we put in the value.

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Now the value is where we do our conversion.

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So we take the temp variable,

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which represents the temperature in Celsius from weather_c,

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and we apply the formula that converts it into Fahrenheit,

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which is to multiply it by nine, divide by five,

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and then add 32, and that will convert our Celsius degrees

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into Fahrenheit degrees.

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And it gets assigned to the value

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of each of the new items in the dictionary.

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This line of code alone on line five is incredibly terse.

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It's incredibly succinct.

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For better or for worse.

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It can be difficult to understand,

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but once you get the hang of it,

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and once you figure out how to read it,

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using, say, the keyword method,

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or whichever method that you are comfortable with,

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then it becomes easier to decode and understand,

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and it can be really, really powerful

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in just one line of code.

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Hopefully you managed to achieve this.

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If not, go back to your code, fix it,

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and make sure you understand what's going on

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before you proceed.

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There's no shame in fixing your code

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after looking at the solution.

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This is all a part of the learning process.