Python for Entrepreneurs Transcripts
Chapter: Python language refresher
Lecture: Demo: Memory game - Implementing the game

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0:01 Now when we have the basic shape of our game built,
0:03 let's go and actually implement it.
0:06 So to get started, there is two basic things we need to keep track of.
0:09 What are the things we could show a user,
0:12 like what colors and what have we shown the user.
0:15 So we'll come over here and we want to define a variable on this object
0:18 so we'll say "self." and we'll just create a variable name out of thin air,
0:21 and that is how you define the variables,
0:23 make sure this happens in the __init__ method, not somewhere else,
0:27 so we want to say "history", and we want this just to be an empty list
0:30 so we can do that with just empty brackets like so.
0:33 The other thing we want to keep track of is we want to have the choices,
0:36 or "plays" let's call them.
0:38 This is going to be another list and this is going to contain
0:41 all the distinct plays that we could have,
0:43 so we might have red, we might have blue, we might have green,
0:47 let's say we are going to have four colors, OK.
0:49 Now, in order to make this a little nicer game,
0:51 let's add some color and some more verbiage,
0:54 but we want to have a short thing to test against,
0:56 so we don't make the user type red they can hit "r" and "b" and so on.
1:00 So instead of putting individual items in here,
1:02 we are going to put something called tuples,
1:04 and this will let us put multiple values for each particular play,
1:07 so we are going to put in here, we are going to say "Red",
1:10 that's going to be what we show the user but what we are going to test for
1:13 is just "r" and then yellow and so on.
1:16 Ok, this is a good start, we are going to improve this in just a minute,
1:20 but let's finish some of the other implementation here and then we'll move on.
1:23 Next, let's turn our attention to show_level();
1:26 I would like to be able to clear the screen, whatever is on there remove it,
1:29 show them just the colors that we've picked or that we have at our current level
1:34 maybe four colors at level four, and then take that away again,
1:36 so we are going to need a "clear" method, so we can say self.clear, like so,
1:41 and we can add that method here, which goes at the bottom,
1:44 we are going to use a pretty cheap way to clear the screen here,
1:46 we are going to go and import one of the system modules,
1:49 so to use something out of the standard library, we have to import it,
1:53 so we are going to "import os".
1:54 Now we could do a little bit of work to test what platform we are running on,
1:57 but I am just going to do it from Mac, you do it for whatever you want to run it in for,
2:01 and you could use the sys module to figure out whether you are on Windows
2:05 or on a Linux Unix based machine.
2:08 But we are going to say "os.system" and call a system command,
2:11 and a system command we are going to do is clear.
2:13 Right, that's what you type in the console or the terminal to clear the screen
2:17 and that's where we are going to have our game here.
2:20 Now PyCharm is giving us a little warning that this doesn't have to be a instance method,
2:24 it could be a static one, but just to keep things consistent,
2:27 I am going to say "don't bother us with that".
2:30 So you won't see any squiggles there.
2:31 Right, so first thing we are going to do when we show the level
2:33 is we want to say "we want to clear the screen",
2:36 and then we want to go through each item in the history
2:38 remember up here we have this list, "history",
2:41 so we'll say "for h in history" and when you... in self.history,
2:44 in Python the primary way to process a collection is to use this "for...in" loop,
2:49 so "for" some variable we make up in the collection,
2:52 so if we have ten items in our history, we are going to pull them out
2:55 and work with them one at a time here, so than we could say "print",
2:59 now, we need to think about what are we going to put into this history here,
3:03 and what we are going to put in are basically selections of these,
3:06 so we want to print out the first element here,
3:08 so there is a couple of things that we can do
3:10 but let's just keep things simple we'll print [0] there.
3:13 The next thing we want to do is also we don't want to have this pile vertically,
3:16 let's have this just go horizontally, it seems like that's a little better
3:19 so we can say the "end" is just going to be two spaces,
3:22 or a comma or something like that. If it prints this out as fast as they can
3:25 and it goes away, that's not going to be so great
3:28 so what we want to do is we want to make it go slowly
3:31 so we can put this thread to sleep using the time method here,
3:34 and we could go to the top up here and type "import time" or in PyCharm
3:37 hit Alt+Enter and say "we would like to just import this name",
3:42 so see how I wrote "import time" at the top, and now,
3:45 it has a handy little sleep function and let's say it's going to sleep for two seconds.
3:49 Now, something that happens in this that you won't see
3:52 until you run it but while I am here I will go and take care of it,
3:55 I'll put a note that we need to flush the output,
3:58 just because the way it works in the terminal this doesn't always
4:01 flush that stream as you sleep, and so it doesn't show in a nice smooth way,
4:05 we'll see that we need to do that here.
4:07 And maybe two is a little long, let's put that at one, and last thing,
4:11 after we are done showing them that, let's "clear",
4:14 this is going to take that screen away, so we are going to show them the history,
4:17 clear the screen, show them all the moves they are suppose to remember
4:20 and then take it away. And then we are going to test them,
4:22 but before we test them, let's add a move, right?
4:25 We've got to start out with the empty set of history,
4:27 let's add some will say self.history to add something to a list we just append to it.
4:31 Now, there is a really nice way to randomly select from a sequence in Python,
4:35 so if we have the random module imported, we can come down here and say
4:41 "I would like to pick one of those random items",
4:43 so I say random.choice
4:47 and pick some sequence and it will just give us one random,
4:52 so that's really nice to write there.
4:54 let's hold off on the test here and let's just say "return True",
4:59 let's just say they are passing for now so we can see the other stuff working.
5:02 All right, so like I said, there is going to be a little bit of a problem when we run this,
5:06 but let's go ahead and save and run this.
5:08 Now, how do we run this? Right-click over here
5:11 and we can say "run" and pick whatever thing it is we want to run, and run,
5:16 now, notice, it doesn't really like this stuff being empty here when we call clear,
5:20 and really we have to just run this outside in the terminal.
5:24 So a simple way to do that is just copy what PyCharm is doing.
5:27 Here you can see something is happening but we are not really seeing this item,
5:31 so like I said, we need to flush this because that's a little bit funky,
5:35 so we are going to say "sys" import that module, go to standard and just say "flush".
5:43 Now let's try this again, so yellow, blue, yellow, blue, green,
5:50 yellow, blue, green, blue- you can see it's just slowly building up as it goes.
5:56 All right, we are of course not testing the user,
5:59 but it looks like this works, except there is one problem,
6:02 something I don't really like so much here, that green is yellow, that blue is yellow,
6:06 everything like that, so we can come over here and use an external library,
6:10 external package that I have installed,
6:13 and I have installed it with "pip3 install colorama",
6:17 so we are going to use this thing called colorama,
6:20 and that lets us add coloring to the console.
6:23 I have already installed that like I said,
6:26 and so the way you use it is you just add in a string colorama.for.red let's say, like so.
6:33 We are just going to do this for each one.
6:36 Let's just run that again, make sure I hit save, and run it,
6:40 and now you see, blue is blue, blue is blue, red, red is red,
6:45 and as it builds up we'll see more of these, yellow is yellow and so on.
6:48 Great, so that feels much more like a game to me.
6:51 Now it's really down just to testing the player,
6:54 so what we are going to do is we are going to go through for each thing in our history
6:58 we are going to ask the user what is the first item, what is the second item,
7:02 and so on and we'll just see if they can get that right,
7:04 so let's start out with the little message to them,
7:06 just to say "look, you are going to need to remember four items", or five items,
7:09 or whatever it is and let's do this white, so we'll say colorama.fore.white
7:13 and then what we want to tell them is we want to say "there are three moves,
7:17 or two moves, or something, we can use this string format style, like so,
7:22 and we can say .format and say I want to give it the length,
7:26 the number of items in this object's history.
7:30 And then for each one of those things in the history we want to loop over it
7:33 and test so we'll say "for h in self.history", we want to test something.
7:40 Now, I'll show you another good trick here, another good technique, remember,
7:44 each thing in the history is one of these
7:46 and what we really care about is the second value, not the first.
7:50 Down here, we were just using indexes into it,
7:53 [0], [1] and so on, but we can do what's called tuple unpacking here,
7:57 so I could say we can give the text and the entry or the "v" for value,
8:02 and because this is a length two tuple, the first value is assigned to you
8:06 and the second is assigned there.
8:08 So we can just test against that "v", so let's say something like this,
8:11 we want to get input from the user, that's super easy, we'll say input,
8:15 use the input method and we just give the prompt.
8:18 And we'll give them a little hint on the things that they can type and then we'll say
8:22 "if guess != v: return False".
8:26 So, the very first time that they get it wrong let's say nope, that was wrong,
8:29 and in the end if they make it through all of them,
8:31 they must have gotten them all right, so we'll say "return True".
8:35 All right, I think our game is just about ready to play,
8:37 let's save it and then run it over here and see what we get; green,
8:42 OK, so it says one move we have to remember, and that was "g",
8:46 OK, worked, green, green, green, green, now red, so "g", "g", "r",
8:55 it really seems to like red and green.
9:00 Let's just put something wrong so we can see that it said "all right, look,
9:04 you entered something wrong", it's supposed to be green, you said red, there it goes.
9:07 But, we made it to level 7, that was pretty awesome,
9:10 but what is even more awesome is our game is totally implemented here,
9:13 so we come in, we create the game, we start out with the empty history,
9:17 and the various plays that we can make, to show the level,
9:20 we just loop over the items and we print out the text,
9:23 and because we are not using an inline, it doesn't flush,
9:27 so we are going to force the flush here, do rest,
9:30 to add a move it's super easy, we get a random one from our plays,
9:33 and to test the player we just go through each one of them, these entries in the history
9:38 and we unpack the values and we check that their guess is the right value.
9:43 There is so many things to learn in Python
9:46 and it's a very rich and powerful language,
9:48 but at the same time, you've seen a significant portion of it, in action.
9:52 If any of this was too fast, or unclear, please go and review the reference section
9:57 where we go over every one of these ideas topic by topic,
10:01 there is something on loops,
10:03 there is something on conditionals, there is something on methods and so on.
10:06 If you need to find out more details about something,
10:09 before you start the rest of the class,
10:11 make sure you check out the reference section.
10:12 Otherwise, let's move on to getting started with web development.