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All right, so how did you get on with today's project?

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Hopefully it went really well and you're just here to see how I did it.

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As I mentioned before, it's really useful when you're trying to create a large project to break it

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down into smaller pieces so that you can tackle each of the pieces one by one.

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And a great way of doing that is by creating your own flowchart.

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So as I've shown you before in the end of the last lesson, this is the flowchart that I've created

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for this particular program, and I'm going to follow it step by step to create this final blind auction

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program.

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The first thing we're going to do is we're going to show the logo from this file art.py, and notice

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how this logo is stored inside a variable called logo.

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The first thing we have to do is to fork our own copy of the starting project, and then we're going

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to look inside the art.py module and then we're going to import that logo.

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So now I can go ahead and print my logo.

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So that's the first step done. Next we're going to ask for a name.

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So that's going to be in the form of an input.

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So let's go ahead and create a variable called name and we're going to set it to be an input.

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And the input is going to say, what is your name?

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So they're going to type in their name and that's going to be stored inside this variable.

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Now, the next thing we're going to do is ask them for their bidding price. We'll say that inside a variable

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called price and we'll create another input to ask them what is your bid?

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And at the end of this, I'm going to add a dollar sign just so that when they are typing their bids,

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they'll see this line.

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And when they start typing, the cursor should be about here so they can see the dollar symbol before

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their price.

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So now we're down to here and we have to add our name and our bidding price into a dictionary.

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Let's go ahead and create it up here and we'll call it bids and it's going to start out as an empty dictionary.

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And then later on, once we've got the name and the price, we said that the name was going to be the

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key and the price was going to be the corresponding value. To add a new entry to our bids dictionary,

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we specify the dictionary, we add a set of square brackets, and then we add the key.

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The key is going to be the name and the value is going to be the price.

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So we would write it like this.

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Now, we get down to the slightly trickier part. We're going to ask if there are any other users who

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want to bid. And if the answer is yes, then we're going to clear the screen and we're going to loop

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back to where we ask for the next name and the next bid price.

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How do we achieve this?

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Well, we can put this into a while loop. Let's go ahead and indent this.

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So I just typed command and then the right-sided square bracket. Or on Windows, it will be control and the right

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side of the square bracket.

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And then we can wrap this into a while loop.

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If we had some sort of variable that would keep track whether if the bidding is finished.

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So let's call it bidding_finished.

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And of course, it starts out being False.

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Now, while bidding is not finished, so while not bidding_finished, so basically while this is still

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false, then we're going to keep running this until forever.

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But of course, we need a way to stop this.

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So we're going to create a new input where we ask the user, "are there any other bidders?"

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Type "yes" or

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"no". This way we get to get an input which is going to be either the word yes or the word no, and

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we can save this inside a variable called maybe should_continue.

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So this way we can check this variable and we can see, well, if should_continue is equal to "no",

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well, in that case, that's when we're going to flip the switch and change this bidding_finished variable

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to true.

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So this means that when we get to the end of this block in the while loop, then when it checks this

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bidding_finished, it's not going to continue to loop anymore.

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Now, on the other hand, if should_continue was yes or in fact any other value, then we can keep continuing

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and we don't actually have to change this variable because it's already false.

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Now we have our code looping, which means that unless the user types in a 'no' at the very end and bidding

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becomes finished, this is this path.

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Otherwise then we're going to keep going through all of these lines of code which is basically all

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of this until we get to the point where this switch actually gets flipped.

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So if you notice that if the user actually answers yes, then we want to clear the screen before we

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repeat the loop.

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That means we can check to see

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well, elif should continue is equal to.

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yes,

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well, in this case, we're going to call that clear() function that I showed you in the hint at the very

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beginning.

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So this function comes from the replit module and it allows us to clear the output in the console so

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that the previous name and bid gets cleared on off the screen and it leaves a fresh start for the next

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user.

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The last thing we have to do is to actually address this right? So when they answered no, they get taken

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out of the while loop, but we still have to find the highest bidder from our dictionary and to declare

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them as the winner.

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How do we do this?

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Well, let's put this in a separate function. So we could create a new function called find_highest_bidder.

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And this is going to get the bidding_record as the inputs, so this will be the dictionary that represents

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all the bids, the names and the values. I think it's easier if we can visualize what this bidding_

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record might look like.

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So we know it's a dictionary of key-value pairs where each key is a name and each value is a number.

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So let's say we had only two bidders, Angela and James.

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Angela bid $123.

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James bid $321.

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So we can see who's clearly going to be the winner here.

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But how do we get our code to figure that out?

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We need to somehow loop through this dictionary, right? which is called bidding_record.

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We know that we can use a for loop to do this so we can say for each bidder in the bidding_record,

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and this is a good point to remember that when you use a for loop on a dictionary, instead of looping

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through each item in the dictionary, like each of these key-value pairs, it actually loops through

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each of the keys.

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And we covered this in the very first lesson of today where we talked about how the for loop works

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when we're looping through a dictionary. Now, we're going to get hold of each of the bidders inside

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this dictionary.

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So what do we do with it?

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Well, we want to use the key to get the value.

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Let's take the bidding_record and pass in the key,

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and this should give us the value.

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So now we can actually save this inside a variable which I'm going to call bid_amount.

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So the first time this for loop runs, the bid_amount is going to equal 123

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and the next time the for loop runs, the bid amount is going to be equal to 321. If we had some sort

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of way outside of the for loop

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that keeps track of the highest bid, well then we could use this number to check against the current

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bidding amount.

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We can use an if statement to check

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well, if the bid amount is greater than the highest bid, well, in that case, then the highest bid

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becomes the bid amount.

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So what this means is that we start out with a zero. The first time the for loop is run, the bidder

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is going to be equal to Angela,

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the bid amount is going to be equal to Angela as the key passed into this dictionary, which is going

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to get us the value 123. If 123 is greater than zero,

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well, then this highest bid is now going to become 123. The next time the for loop runs

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the bidder is now James and the bid amount is now 321.

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Now we're checking if 321 is greater than the highest bid.

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Remember this, in the last round, got set to 123.

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So this is going to be true.

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And this means James' bid, 321, is now going to be the highest bid.

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In addition to keeping track of the highest bid, we can keep track of the winner. If this is indeed

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true, if the current bidder has the highest bid, well then at the same time as setting the highest

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bid,

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we should also set the winner to the key,

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so the current bidder.

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And once we've gone through this for loop and we've looped through all of the records in the bidding record,

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well then finally we can actually print

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"The winner is..."

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the winner that's stored in this variable. And we're going to say they won with a bid of... and let's add

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a dollar sign and then we're going to pass in the highest_bid.

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Now, we can turn this into an fstring and it will use both of these variables, which is storying

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the highest bid and the winner's name to print out who the winner is.

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So down here, when should_continue is no going down this path,

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we can now print and declare the winner. In addition to saying that bidding finished is true,

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we're also going to call that function, find_highest_bidder, and pass in all of the bids that we

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have been keeping track of over here.

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Now, just before we run our code, let's go through each line and make sure that everything looks all

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right.

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Firstly here, where it says, 'what is your name?'

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maybe we can add a colon and then a space

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so the user starts typing here.

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Then it asks, 'what is your bid?'

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We can add a colon as well and the user will start typing after the dollar sign.

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Now, I can already see a problem that's actually going to happen because of this line 23.

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I wonder if you can spot the issue here, especially if you think about what we're going to do with

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this price later on.

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But I'm going to add one more new line here and then I'm going to run the code and we'll see what actually

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happens.

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So now let's go ahead and run the code.

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And you can see our gavel printed and then it asks us for our name, so I'm just going to put my name and

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then 123. And then one other bidder who's going to be James, 321.

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And now if I say no, there are no more bidders,

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see what happens when I hit enter.

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I get a type error

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and it tells us that the greater sign is not supported between instances of a string and an int

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and this happened on line 16.

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If we take a look at line 16, basically we're comparing the bid amount, which is the value that came

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out of the bidding record, which is what's being passed in here,

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and that, of course, is a dictionary where the keys are the names of the bidders and the value is

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the price.

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So what's actually happening here?

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Well, it's because when I took this price input in, I kept it as a normal input.

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Instead, it should be turned into an integer.

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So that way we can work with it as a number so that when we're comparing it against, say, zero or

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whatever other number later on, it can actually do the comparison.

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It doesn't actually make sense to the computer when you're comparing a string versus a number. That doesn't

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actually work.

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And this was covered when we talked about data types in Python.

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Now, if we hit run again

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and we do the same thing, and when I say no, you can see that it tells me the winner is James with

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a bid of 321.

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Essentially, the hardest part of this challenge is figuring out how to loop through a dictionary and

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get hold of each of the bidders and each of their values and compare them historically against previous

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values inside this dictionary.

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If this function is confusing to you, then I really recommend either going over to Thonny, pasting

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the code in and exploring it by going through it step by step.

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Alternatively, if you can't install Thonny or you don't have access to your normal computer, then you

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can also go to a website called pythontutor.com.

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And this also lets you visualize your code, although in a slightly more simplified way. If I go ahead

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and paste in my function, find_highest_bidder, passing in the bid record, let's go ahead and create

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a new dictionary of bids.

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So now we have a dictionary of bids with two key-value pairs just as we entered before,

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and then I'm going to call this function, find_highest_bidder, and pass in these bids.

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Now, if we go ahead and click visualize execution, you can see it's going to go line by line, and we

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can click next to see how it's jumping through this.

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Firstly, it's bypassing this function, creating this next dictionary.

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So now it's got a function stored somewhere, which is this one,

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it's got a dictionary called bids stored somewhere else.

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And now we actually get to the line, which is going to execute that function and it's going to pass

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over this dictionary of bids to this function.

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And if you step through this line by line, you can see it creating these new variables and populating

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them. The first time we run it

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the highest bidder is zero, the winner is an empty string, and the bidder in the for loop is now Angela.

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It's the first key from the dictionary as it points to here.

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Now if we keep clicking

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next, it works out the bid amount which is the value corresponding to that key, and then it works

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out the highest bid by comparing whether if the current bid amount is greater than the current highest

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bid.

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So 123 is greater than zero

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so when I click next, you'll see highest bid gets replaced with the bid amount and the winner is now

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going to be set as Angela. The next time the loop runs the bidder is

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now James, and if I keep going through this, you can see that James actually ends up with the highest

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bid and becomes the winner.

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So now the for loop is done because it's looped through all items in the dictionary and it's now going

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to print the output, which is 'The winner is James with a bid of $321.'

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This is another way that's really, really helpful to visualize your code.

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And the other great thing is that even if while you're visualizing there's still something you don't

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understand, you can actually click on this button to get live help from users across the Internet.

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And if you want to practice your own debugging, just as we did in today's lesson, you can also click

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to help some of these users who are looking for help with their code.

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And you can practice reading code, understanding code and helping other people with their bugs and

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their issues.

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Finally, if you want to take a look at the completed code for today's project, then as always, you

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can head over tor repl.it/@appbrewery/blind-auction-completed.

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And it's important to remember that this is just one way of completing this project.

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There are lots and lots of other ways. But as long as you test your program thoroughly and it works

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in the same way, then it doesn't matter too much how you've done it.

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But it's important that you've absorbed the knowledge in today's lessons, and the most important of

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which is this concept of dictionaries, adding to dictionaries, and also looping through dictionaries.

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So have a look through the completed code and also have a play around with Python Tutor, which is

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a really great resource for your learning.

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And I'll see you tomorrow for more lessons on Python.