Original subtitles

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Now that we've learned all about loops in Python,

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we're finally ready to tackle our final project of the day,

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which is the PyPassword generator.

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Our program will ask us how many letters would you like in your password?

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So I will say I would like a long password, let's say 14.

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How many symbols, 3, how many numbers, 4,

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and it's going to generate me a password that is almost completely impossible to

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crack by any hacker, no matter how talented they are.

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So the project of today is to build this password generator.

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If you head over to this particular Repl.it,

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password-generator-start, then you'll see that here

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I've already included for you a list of all the letters in the alphabet from A

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to Z, including the uppercase and lowercase letters.

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I've got a bunch of numbers and a bunch of symbols that are usually accepted by

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websites in the passwords.

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And I've also created the inputs that you saw when we did the demo.

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So it's going to ask us how many letters, how many symbols, how many numbers,

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and then you're going to turn all of that knowledge as well as using these

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lists

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and what you've learned about loops into the same password generator that you

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saw in the final demo.

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So have a play around with the final demo yourself,

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and then have a think about how you might be able to achieve this goal of

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creating a random password for the user based on the number of letters,

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symbols, and numbers that they want.

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Now there's two levels to this project.

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You can either go for the easy version where all you have to do is generate your

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password in sequence. So for example, if the user wanted four letters,

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two symbols, and two numbers,

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then it might just look like this four letters and then two symbols and then two

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numbers. So they're in sequence right? First, you've got the letters,

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then you've got the number of required symbols,

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and then you've got the required numbers. So this is the easy level.

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And then there is the hard level. And the hard level requires you to generate the

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password in a completely random order.

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So instead of having it being, letter symbol number,

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it should be maybe letter and then a symbol and then a number,

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then a letter, then a symbol and then a number.

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But notice how this is completely random.

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Every single time you generate it,

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the order of where the symbols and where the numbers appear in your password are

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completely random. So for example,

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if you look at the demo version and I do the same thing,

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four letters, two symbols,

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two numbers, where the numbers and where the symbols occur are completely

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unpredictable. And every single time I generate a new password,

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it's going to switch it up again.

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So that's the hard level. I recommend trying the easy level first

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and then once you've managed to do it, then take yourself up to the hard level

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if you think you're up to it. But remember that if your doing the hard level,

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you might have to do a little quick Google around in order to figure out how to

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do something that you might not have seen before.

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But it's all part of the challenge and I hope you'll take it on with vigor.

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So pause the video now and try to complete the final project.

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Alright,

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so let's first tackle the easy level where we're just generating a password

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with the required number of letters and then the required number of symbols and

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then the required number of numbers.

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So let's go ahead and tackle this one first.

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Now we know that we've got these lists which we can draw from,

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and we know that we can use the random module to get hold of a random item from

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the list. So all we have to do is first get four random letters.

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So let's say that we had a password

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which just started out as an empty string.

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Then we can use a for loop to loop through all of the characters that we need to

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create for our password. For example,

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I might say for char, short for character, in the range of,

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um,

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from 1 to the number of letters that the user wanted.

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So in this case, if the user wanted four letters,

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then it will be a range from one to four, but not including four.

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So it's actually from one to three,

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which has only three characters. In order to modify this,

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we have to do what we did always before,

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which is just to add one to the end of our range.

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So now we're going to create a range based on the number of letters that the

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user wanted.

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And I'm just going to go along with the assumption that the number of letters

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equals four. Let's just pretend that's what the user will enter.

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So then this range becomes 1, 2, 4 + 1 which is 5.

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So the range is in fact going to be 1 to 4. For every single number in that

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range from one to two to three to four,

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I'm going to generate them a random letter,

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and I'm gonna pick it out of this list of letters. To do that

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I can either generate a random number and use it as the index or you might've

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seen previously

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I showed you the random.choice function. And inside this random.choice,

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we can pass a sequence

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which in our case is the letters list.

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Then it will look through this list of letters and it will give us a random item from

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that list.

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So now that random letter is going to be something that we're going to need to

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add to our password, right?

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So we can set this equal to a random character.

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And now let's go ahead and just print it out.

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Right?

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So let's say we want four letters in our password and we can type anything for

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the other ones, but notice how when the for loop runs,

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it's given us some random characters that it's picked out of our letters list.

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So there's an a,

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there's a capital P there's a d and there's a capital J. How can we add each of those

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letters to our password? Well,

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we can use the string concatenation that we learned very early on in Day 1.

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We can say password equals the previous password

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plus the random character. Of course,

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the shortened version of this is just password+= random_char.

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And now let's go ahead and instead of printing the random character,

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let's print the password at each stage of the loop.

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Right?

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And again,

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I'm going to choose four letters and you can see that the first time the loop

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runs I get an M. So password is equal to M. The second time I get a Q

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so I add the Q onto the M, I get MQ and so on and so forth until I get these four

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characters in the beginning of what seems to be my random password that's going

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to be generated.

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Right

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Now, if you wanted to,

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you can actually simplify this down to just one step,

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because instead of having this intermediary,

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which is the random character variable,

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we can simply just replace it with the code, like this.

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So in this case, we're getting a random choice from our letters list,

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so we get a random letter, and then we add that to our password.

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Now that we've done that for the letter,

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then it's pretty easy to see how we can continue doing this for the symbol and

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the numbers. We just have to keep adding it to the end of our password.

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So let me quickly write out the code for this.

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Right?

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So now when the user requests that they want four letters in their password,

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then we generate a range from one to five.

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And then for each of those positions,

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we generate a random letter in order to fill the password.

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And then we add on the required number of symbols and the required number of

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numbers. And finally, we print out the final password.

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Let's go ahead and run this code. And again,

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I'm going to choose four letters, two numbers, and two symbols.

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And I end up with my final password,

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which fits exactly that criteria and it looks pretty random.

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But the only problem is that if a hacker knew that you always have two symbols

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at this position, and two number at this position,

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then it's very easy to crack that password because in order to get the last

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digit, for example, they only have to try nine different variations, 12

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3456789.

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And this just limits the strength of your password. In order to tackle that you

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would have to tackle it at the hard level,

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which is how do you get a password that has all of these letters and numbers in

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a completely random order. To do that

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we mentioned that you have to do a bit of googling because it might require

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something that you haven't done before. But in essence,

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you've got access to everything you need to perform the logic.

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So if you haven't given that a go,

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then this might be a good time to pause and have a think about how you might

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structure the logic or how you might create a flow chart to express this logic

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that you would want. And once you've done that,

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and if you want to see the solution and walk through it with me,

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then come back here and I'll show you how to do it, but first give it a go.

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Right?

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All right. In order to tackle the hard level,

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what we essentially need to do is instead of adding each of these letters into a

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string, we actually want to add it into a list.

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So I'm going to copy all of this that's here,

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and I'm just gonna comment it out and I'm going to paste it under my hard level and

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work on it here. So instead of using a password string,

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I'm going to create a list and to better describe it

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I'll change my variable name, the password list. So now,

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instead of using password to add each of these letters and numbers and symbols,

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I'm going to be adding it to my list.

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Right,

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Right,

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Right

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Now, to add things to a list,

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you can use the same syntax that you did with strings,

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which is to add the new item into the list and to update the old list.

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You might be more familiar though with the syntax

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which is append and both of these work.

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You can use either of them if you want, but they'll end up doing the same thing,

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which is to add each of those things you've generated in the order that you've

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generated to your password.

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So we end up now with a list with four letters,

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two symbols, and two numbers,

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all stored as strings because of the quotation marks around them.

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So now that we've got a list, well, then we have to think about, well,

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how can we shuffle our list,

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how can we mess up the order of the items in our list?

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And that might take you to Google and you might search for something like how to

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change the order of items in a list.

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And then we also have to add our keyword, which is Python,

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because there's obviously a lot of other programming languages.

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And we come up against our first Stack Overflow question,

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how can I reorder a list? Well, that sounds kind of like what I want to do,

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right? So if we scroll down,

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you can see that the way to do it is either using a for loop,

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like so, or

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to simply use the shuffle function.

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This is a much simpler way because it allows us to update the existing list just

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by calling the shuffle function on it.

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And this one actually requires us to create a new list and we have to create a

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bunch of random numbers for the order,

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and then to reorder them using a four loop.

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So I'm going to go with this version and let's try it out.

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Instead of printing password_list,

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let's print the password_list before the shuffle,

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and then let's use the random.shuffle and pass in the password_list.

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And then let's print the outcome of that shuffle,

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so let's print the password_list again.

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So now you can see that we've got a version before,

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and then we've got a version after.

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So if I run my code and I write again, four letters,

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two symbols, two numbers,

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you can see that previously it was ordered in the order that we added each of

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the characters. After the shuffle

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they're now pretty much random. There's letters in random places,

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there's symbols in random places.

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So if only we could turn this back into a string,

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then we've got our password that's nicely shuffled.

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So how can we turn it back into a string? Well,

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we could simply use a for loop, right?

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We could say for each, um,

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character in the password_list,

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we're going to add it to a variable called a password,

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which is going to start off again as a empty string

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and then we're going to add to it.

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So we're going to say password += char in our password_list.

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And now if I go ahead and just print my final password,

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I'm going to add a fstring as well.

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Let's say your password is,

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and then let's insert the password.

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And now if I run my code and let's say,

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I want 12 letters, uh,

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three symbols and four numbers,

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then it's going to generate me a entire password

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that's completely randomized in terms of the orders of the symbols and the

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numbers.

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And I've now solved the hard part of this challenge project.

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Did that make sense to you? Did you manage to get it

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to do what you want it to do?

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If you're at all confused about the code that we've covered here,

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then be sure to check out the final project that I've got here,

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which is the App generator end,

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and take a look at how the easy level is implemented,

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how the hard level is implemented and try switching it around so that you really

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get to understand it.

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Try instead of maybe getting the user to tell you how many letters,

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how many symbols, how many numbers, instead just define those yourself

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or use a random number of letters, numbers,

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and symbols. Play around with the code until it starts doing what you want it to

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do and it starts making sense.

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But I hope you had fun building this project with me today and learning all

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about loops. On the next lesson

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we're going to be learning more about these things that we've been using a lot,

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which is Python functions. So I'm going to bid you goodnight for today,

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and hopefully I'll see you bright and early tomorrow,

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and we'll learn some new skills and work on some new projects.

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So that's all from me, goodnight from Angela.