Original subtitles

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Previously we saw how the Len function gives us a type error when we give it a

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number instead of a string.

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So let's talk a little bit more about data types and functions.

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And the way I think about functions is kind of like some sort of fancy machine

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that you might see in a factory, right? So in this case,

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we've got some sort of machine that's going to take potatoes into chips and we

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don't really care how it does it,

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but it's probably going to have to peel the potatoes, wash the potatoes,

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cut it up, fry it,

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and then finally return it to us as an output in the form of fries.

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And if this is the first time that you're watching one of my tutorials, um,

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this is probably a health warning. I talk about food a lot. Um,

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so be prepared if you haven't eaten.

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Now let's say that we took the same machine that normally processes potatoes and

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we decided to get a rock and we just pass this through the function,

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then we're getting an error, right? This is basically what happened here.

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This length function doesn't like working with integers.

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And by forcing this through,

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we end up with an error and our code breaks and it gives us this thing, a type

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error.

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Now do you remember previously we had this challenge where we asked you to get

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the um, get an input from the user, what is your name?

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And then we use the length function to get the number of characters of their

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name. And let's just save that to a variable. Let's call it, um,

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num_char equals this.

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And then we print your name has plus num_char, number of characters + characters.

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So in this case you would expect it to prompt the user to enter their name.

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Let's say I entered my name Angela,

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and the length of that string would be 6

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so this would be equal to six. And so this would get substituted in here.

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And then with string concatenation, we end up printing

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"Your name has six characters." But this is not what happens.

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And I know that some of you might have tried this for the previous challenge and

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you would have gotten a type error.

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So it tells you that you can only concatenate strings,

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not integers. So in this case,

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we were concatenating a string to an integer.

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This is what we get. We end up with an error.

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So how can we prevent these type errors and how can we see the data type that

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we're working with? Well,

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we could use a function called type,

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which basically will check whatever you put between the parentheses and give you

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the type of data that it is. For example,

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if I go ahead and just comment out this line of code

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which breaks and go ahead and put num_char,

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so this particular piece of data inside this type function,

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and then I'm going to print the type of num_char.

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And now if I hit run, let's enter my name.

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And you can see it's telling you that this is an integer.

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So adding a string to an integer doesn't make any sense,

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which is why you got the type error.

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Now every so often when you're writing code and you're not quite sure what the

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type of data of something might be,

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then you can simply just put it inside a type check function,

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right? Like so. And then you'll get an answer.

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Now in addition to type checking,

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we can also do type conversion or you might hear it called type casting where we

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change a piece of data from one particular data type to another.

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So it, for example,

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we know that this variable num_char has the data type of integer.

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If we wanted to turn it into a string so that this line of code wouldn't break

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anymore,

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then we could convert it into a string by writing str

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and then inside the parentheses, we put in the variable that we want to convert,

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which is called num_char. And now we save this into a new variable,

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we'll call it new_num_char.

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And once we've converted this into a string and stored it under this name,

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then we can use it inside our print statement, new_num_char,

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and now it won't break anymore. And it tells us your name has six characters.

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So in this case we've taken a integer data type,

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put it inside the parentheses of a str function,

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which takes a object in between the parentheses and converts it into a string,

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which we then store inside this new_num_char

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and we can now use it in our print statement because all the data types of all

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the pieces of data that we're adding together have the same data type, string.

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Now you're not limited to only converting numbers into strings.

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You can convert a whole bunch of different data types.

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So let me go ahead and comment out this code and I can show you that

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let's say that we had a variable a, which we set two a number,

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right? 123.

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And if I do a type check on a and print this,

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you'll see that as you would expect, it should give you integer, right?

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A is an integer.

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But now let's say I converted a into a string by wrapping it inside the string

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function, then hit enter. You can see it's now of type string.

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Now I can do this with other things as well. So for example,

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I could turn my whole number here into a float and when I run my code,

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now we see that the type of my variable is a float

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and that's pretty straightforward, right?

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But let me ask you two quick questions before we wrap up.

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What will this line of code print? Alright, you guessed it,

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this will print 170.5 but what's actually happening behind the scenes is we're

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converting this string 100.5 into a floating-point number and then we're adding

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70 to 100.5 and finally we're printing the results.

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But what about this line? What will print here? Have a guess.

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Well, this time we get 70100. So in summary,

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you can use the type function to investigate the data type you're working with

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and you can use functions like string, int, or float to convert to that data

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type. In the next lesson, I've got a coding challenge for you.

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So head over there and we'll get started.