Python for Absolute Beginners Transcripts
Chapter: Organizing and reusing code with functions
Lecture: Selecting the roll quickly
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Let's look at what I consider to be a bit
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of a drawback for our game here.
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If I run it, I have to type scissors.
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And if I misspelled scissors, like 'ssors
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then, whoa, whoa, that's not a valid play
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you got to go again.
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Wouldn't it be nice, wouldn't it be easy, if it could just
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press one for rock
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two for paper
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and three for scissors?
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That would be cool.
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That's what we're going to do now.
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Also, going to let us look at a cool different type of loop
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while we do it. Now, let's go back here and kind of go through this
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higher view of our program that we have
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because we're using functions.
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So show header, we don't need to mess with that.
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play_game, that's probably the place we have to go.
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And then in here, this is the part that
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asked the user to input something
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and then it gets it back.
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So all we have to do is change get_roll
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and if this was used in many different places
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this change would automatically be picked up everywhere.
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That's cool.
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So we're going to jump down here to this
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and what we can do is instead of that doing that, there
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Let's go and show them the rolls.
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So I'd like to print out something...
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I'd like to print out what various role options there are
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so there's a really cool way to do that.
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Anytime you have a list or some sort of collection
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or sequence of things
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you can go through it using what's called a for in loop.
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And it's incredibly simple, all you do is say something
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like this for r in rolls.
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Each time, for each role, there's three...
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So this sweep will run three times
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you can just print r
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Let's just print it like this for a second.
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Let's go and run that and see what happened.
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Here we go. Look how cool that is.
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So all we got to do is, for thing in collection
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now work with the thing.
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Well, that's not a huge difference, is it?
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It just puts them out, top to bottom
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vertically instead of horizontally.
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So let's not do exactly that.
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Let's add a little bit more to it.
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What I like to do is show a number.
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Now, we could come over here and do this weird thing
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where I have index equals one.
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We could print a little f-string here.
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So we could say curly, and we could say
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index not, and then the roll.
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And here we could have it get bigger by one.
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Here we go. 123.
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That works. But it's very much not the right way
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to do things in Python.
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So instead, let me just give a little head right here.
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You can get spell checking, by the way, which is cool.
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We go like this.
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So instead of doing this, what we can do is we can say
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I would like to get the object and it's index.
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The way we do that is we say enumerate
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and we pass the thing we would have looped over
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and we get back here is two things.
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We get the index and the role.
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So forget that part right there.
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If we run this, it's going to do exactly the same thing
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but we don't have to do extra work
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to do sort of bookkeeping of those numbers.
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Close to what we want, but not quite.
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012. All the numbers in Python start at 0
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indexes start as 0, and so on.
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So this might be fine but its a little weird for people
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it's also not very handy for putting your
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fingers near the numbers.
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So what we can do is we can say start equals 1
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and this is a way to pass data to this enumerate function
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and be more explicit.
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Say, there's a bunch of things that have default values
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I don't care about them, but this one called start
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let's set it to 1.
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We try again. Boom. There we go. 123.
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That's great but the input is still expecting us to type in
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rock, papers, or whatever.
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Instead, let's change this...
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elected index or something like that.
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And in order for this to be, remember, a number
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not a string, that just looks like a number
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we have to convert this input to there.
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So we could either wrap it like that
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or we can come over here and make a separate variable
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so it's more obvious.
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Actually, what did I call it?
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I called it test. There we go. We could be like this.
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Now we don't have to ask them for the roles
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instead we have to ask something else.
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So what we need to do, is we need to know that this number
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is going to be between sort of one to the number of roles
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but remember what did I just say?
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That indexes start at zero and they actually go up to
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1 - length, it's a little bit weird.
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It takes some getting used to.
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So we need to adjust that back to convert
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from a human thinking, from 123
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back to computer thinking, 012.
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It's a weird thing but it happens in almost
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all the programming languages, so we'll just go with it.
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And then instead of this role thing here, we'll have to say
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if selected index < 0, <= 0
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or selected index is >=
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Actually, zero is okay because we adjusted it.
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But if it's great than the length of the roles...
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That's how many lengths there are in that collection
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the way we do is like so.
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Let's change this to selected_index + 1
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so that in their mind
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Hey. They still see it as that one they've selected
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and we could actually just put text.
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That would be easy.
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It'll say it's out of bounds.
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And then here we need to return the role from the index.
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The way we do that is we go to this collection.
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We say, I know you're a bunch of things
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I want to get one at a certain position that we've selected
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but we'll just say selected index, like this.
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Go to the collection.
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Pull out the one that they typed in.
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This way they don't have to type scissors, rock
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or whatever we end up expanding this to in the future.
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You just type 123.
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Let's try that.
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Which one do you roll?
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How about two?
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We say two, you roll, paper. Cool, right?
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That was rock. Okay.
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Score is we're up one, we haven't won one of these yet
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so that's cool. Let's play scissors.
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There we go, we rolled scissors.
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We'll roll scissors again.
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Oh, computer won. Let's roll scissors again.
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Let's play one, throw some rocks
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or else we're in trouble.
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Hi. This is it for all the marbles, unless we tie.
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Whew, it was a tie.
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Let's throw rocks again.
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Man, we haven't won one of these games yet, have we?
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Crazy. But there it is, at this cool way of working with
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four in loops, allows us to list out all the items.
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Because we want to give them a number
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we can use enumerate and say go 1234
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and give me the item that goes with it.
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Let's us ask the player for just some kind of number
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in a one, or a five, or whatever the possible options are.
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I guess we haven't tested our logic.
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If you enter five right now, it's out of bounds.
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We enter zero, it should be out of bounds.
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Not for the computer, but remember we adjust
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that to be one fewer.
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We put minus 100, still out of bounds
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but one, one works.
