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In the previous lessons today,

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we looked at how we can use the JSON format to store and load data into our

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program.

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We also looked at how we can use the try, except, else, and finally keywords to

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handle exceptions in our program to make sure that it doesn't fail and end up

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crashing our program so the user ends up with a bad user experience.

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Instead, we can anticipate the things that might happen. For example,

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the first time when we run our program,

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we might not have a data.json file and we deal with it accordingly.

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Now, all that's left to do is to put in the last bit of functionality,

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which is the search functionality, because after all,

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we don't want to be digging through a JSON file to find out all email and

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password combinations for the websites that we've stored.

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So what we want to be able to do is to add a search button

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and it's going to look very similar in size to the generate password button

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and it's going to be in the same grid column. Now,

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when we type in a website and we hit search,

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it's going to look through our JSON, find that data,

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load that data up and look through it for a key that matches the one the user

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typed in. If they find it,

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then we get a pop up showing up and it tells us the email and the password

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that's associated with that account.

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So you've actually done all of this before. Creating tkinter widgets,

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laying out tkinter widgets,

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creating message boxes or these popups and giving it a title,

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giving it a message.

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You've also seen how you can load JSON data and get the data in the format of a

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Python dictionary. Now, once you have the Python dictionary,

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then you can use your usual dictionary methods to try and get hold of the data

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that's inside. And finally,

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you also know how to deal with exceptions.

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So remember, there might also be an exception in this case,

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because if this was the first time that we were running this password manager,

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and in fact,

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we hadn't stored any websites or any emails or passwords in our database,

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then if you hit search, it might actually just give you a file

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not found error as well. So there's quite a few components involved,

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but I'm pretty sure that you can actually get this to work.

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So the end outcome you're looking for looks something like this in terms of

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layout,

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and you should be able to test this so that when you start out without a data

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.json file and you hit search, it should tell you error,

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No data file found.

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But, if you had saved a password under that name and you added it to the

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database, then you try to find it,

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then it should find you the email and the password that you saved.

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So this is what you're aiming for

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and I'm pretty sure that you can do it with just a little bit of thought and 

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a little bit of time spent problem-solving. Once you're ready,

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pause the video and give this final challenge a go to complete the password

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manager

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project. Good luck.

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Alright, so I hope

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you gave that a good go. And as I always say, if there's no struggle,

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there's no learning.

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So make sure that you've allocated at least 20 minutes to trying things out and

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figuring things out and debugging and just messing with the code yourself before

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you're coming to the solution. But all right,

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I'm going to walk through the solution with you together.

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And the first thing we're going to do is we're going to add a button next to our

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website entry.

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So right here. Now notice how we've got our three columns in our grid system.

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So our search button is going to go in pretty much in the same column as our

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generate password button. So let's go ahead and create our

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search button.

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This is going to be a button with the text that says

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Search.

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Now, once we've created that, let's go ahead and lay it out

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uusing the grid system.

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Now the search button is going to go onto the grid in the same row as the

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website label and the website entry. So that is row 1.

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So let's go ahead and add row equals 1 and column-wise,

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it's going to go in the same column as the generate password.

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So that is a column 2. Now, if we run our code, as it is

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however,

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you'll see that the search button seems to be sitting inside the entry.

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And the reason is because initially when we created this entry,

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we gave it a column span of 2

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so that it spans this second and third column.

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So we have to change that.

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Let's go and find our website entry and delete this column span equals 2.

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So now you can see that this has a column span of 1,

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so it's only in this middle column,

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but it's so large that it's pushing the rest of our layout out of the way.

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So what we need to do is we need to make this entry

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the same width as the password entry

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so that it'll actually fit into our layout.

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So our password entry has a width of 21.

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So our website entry is also going to need to change down to a smaller size.

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Now you can see the entry is now the same size and its looking a lot better. If

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you want, and this is really not strictly necessary

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but I think it's quite neat, is you can tweak and adjust the width of this search

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button so that it's roughly the same as the generate password button.

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Now this button is this width because it's what is needed to accommodate all of

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the words in that button, but we can manually change the search button

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so that it's about the same width.

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And in this case, I'm literally just using trial and error to figure it out. Width as

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10 looks maybe a little bit small, let's try width of 13

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and it looks just about right. Now that I'm done with my layout,

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it's onto the next part which is adding functionality.

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Now the functionality is going to come when the search button is pressed.

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So I'm going to add a command to this

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and the command is going to call a method which I'll call find_password. We've

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got generate_password and we'll now have find_password.

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Now I'm going to go and create my find_password.

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And just because we've got all these sections set up, I'm going to add 

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another section which I'll call find_password. Inside

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the section is where we're going to be creating our

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find_ password function. And this find_password,

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let's just check to make sure there were no errors here

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and we've spelled at the same way.

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And this find_password function is going to need to get hold of the entry

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that's inside the website entry.

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So the website that we're looking for comes from the website_entry.get,

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and then we'll be able to get the value of whatever the user typed inside this

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entry.

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And then we're going to use that to search through our data.json.

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Now the easiest way for this to work is actually to first add a website.

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So I'm just going to generate a website with my email and password and add it so

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that it gets saved inside my data.json.

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This way I'll be able to print things and I'll be able to work with the data a

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little bit easier.

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And then we'll address the exception catching a little bit later on.

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What exactly are we looking for? Well,

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we're looking to load up the data inside this JSON file.

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So we're going to be opening up that file.

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So with open and then the filename is data.json,

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and then we'll save this as the data_file.

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Now, once we've got our data file,

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then we can use our JSON module to load up that file

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and we're going to be getting hold of the data that's inside.

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So we can save this to a variable called data.

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Now this data, if I go ahead and print it,

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you should remember is basically just a dictionary.

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So as soon as I hit search, that should trigger this find_password

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and now I've got my dictionary printed in here.

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So what do we want to do with this dictionary? Well,

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we want to look through it and check to see if this website that we're searching

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for actually exists inside that dictionary.

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The way we do that is we say if website in data,

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well, in that case, it's actually success, right?

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We've managed to find it inside the data

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and we now just need to get hold of the email and password values.

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So let's create a variable called email and we want to pick out this particular

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value from this dictionary.

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If this is the entire dictionary,

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then we want to get hold of the dictionary and pick out the item with the key

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that matches the website that we're searching for, like this.

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Now, once we've gotten hold of this,

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this is going to be a nested dictionary.

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So it's equivalent to basically this part of the dictionary.

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So this in itself is the dictionary,

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which you could save to a separate variable,

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but I think it's actually easy enough to understand that we can tag on another

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key here

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which is the word email in order to get hold of the value that's associated with

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that key. So that way,

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this email variable now saves this value here.

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And in the same way, we can get the password from data

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getting hold of the data under the website key and then passing in the password

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key. Now that we've got the email and password,

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we can go ahead and create our message box using show info. And we'll set the

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title to be the website that the user is searching for

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and the message is going to be a f-string,

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which has the email listed.

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And then on a new line,

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it's also got the password that's going to be listed as well.

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Like that.

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Let's go ahead and run this code and make sure that it works.

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Let's say that we have a couple more passwords that we save in here.

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Now I should have three entries, Amazon, eBay, and Twitter,

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and I want to go and search for my password for eBay.

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Once I hit the search button, it goes into that find_password function

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and if it finds that one of these has the key eBay,

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then it's going to fetch all of these relevant pieces of data that I wanted from

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that JSON file.

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So now what we have to do is to make sure that we catch any exceptions that

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might occur and you might already have realized that this works really well

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right now because we have data

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and because we have this data.json file.

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But the first time that I run my program,

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this is not going to exist.

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So this is a more realistic version of what the program will look like

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the first time we run it. And the first time that we go ahead and run this

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and I search for something that is going to look for a file that doesn't exist

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immediately, our program crashes, and we get the file not found error.

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So what we need to do is we need to be aware enough that these things like

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opening files can fail.

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So what we have to do is we have to catch the exceptions and handle them.

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Let's go ahead and indent this entire block and put it inside the try.

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Now, the part that's most likely to fail in fact,

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the first time the program starts, this is definitely going to fail.

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But what we want to do is we want to catch the exception

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that is file not found error. And in the situation,

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what we want to do is we want to create a message box that tells the user

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this data file doesn't exist.

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This is just a simple showinfo

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and we'll give it a title of error and we'll give it a message of no data file

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found,

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or you can put any other message you can think of. However,

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if we were successful in opening this file,

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then this is the part of the code that we want to implement.

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So let's go ahead and bring it up to the right indentation.

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And we searched through our data,

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look for this website and then give the user a popup if it exists.

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Now, if we run our code again and we search for something

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even though we don't have a data file, we haven't saved anything yet,

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then we get this error popup and it tells us no data files found.

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And hopefully the user would realize, well,

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actually I haven't actually saved any passwords.

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So there's one other situation that we haven't yet addressed however.

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If I had, um, let's say Amazon, um,

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eBay and Twitter saved in my JSON file,

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but I decided to search for something that I never saved.

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Let's say my details for Facebook. Well in this situation, actually

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nothing really happens. And it's a little bit confusing because for the user,

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it seems like our program just doesn't work. But in fact, we

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as the programmers know what the problem is. It's basically this

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if statement is coming out as false. The website doesn't exist in the data.

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So none of this gets carried out and the function ends.

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That's probably not the best user experience. Instead,

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we probably want to catch it with an else statement and we want to use a message

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box to tell the that again,

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there is a error in this situation

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but the reason for this error is because

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there are no details that currently exist for the website that they're searching

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for. That way

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they're not sitting there confused as to why searching for some sort of website

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doesn't actually come up with anything.

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It tells them that there are no details and they would have to add it

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if they wanna find it in the database.

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A lot of students might be wondering at this point, well,

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why don't we catch this with some sort of exception?

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And in fact, we could create an exception.

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We could raise an exception here and then we could catch it somewhere else and

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show this message box.

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But the thing you want to keep in mind is that if you can do something with if

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and else very easily, then you should stick to if and else.

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If you can't do it with if and else very easily, and it's actually an error

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that's going to be thrown that you don't have any other way of dealing with,

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then you should be using the try, except, else, finally, keywords.

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And in fact, if you think about this,

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I don't have an easy way of checking to see if this data file ends up being not

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found. But I do have this file not found error

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which is going to be thrown every time that I try to open a file and that

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doesn't exist.

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The other way to think about it is that an exception is something that is

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meant to be exceptional. It's something that happens very rarely.

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Whereas if and else catches things that happen frequently.

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It's pretty often that your user might search through the website

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thinking that they saved some sort of details for a website. But in fact,

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they didn't. Think about this when you're writing your code

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and remember that only use exception handling when you don't have an easy

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alternative. There you have it.

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That's the completed code for our upgraded password manager.

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If you want to take a look at any of this code,

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then, as always, head over to the course resources

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and you'll see a link to the completed code that you can review.

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But in today's lessons,

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we added a lot more knowledge regarding things like error handling and saving

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data in JSON formats and handling and loading and updating and dealing with

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all of that data in order to create this fully-fledged password manager project.

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Now, I'm sure there's a lot more improvements you can add to this,

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but it's going to go beyond the allocated time for today's lessons.

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So if you want,

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please continue messing around with the code and improving it and make your own

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customizations and modifications.

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If you create something that you thought was cool,

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then be sure to share it with us in the Q/A below the lesson so that we can

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all admire your hard work and maybe improve our own code as a result.

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So have fun playing around with this program and I'll see you tomorrow.