Lesson video

Hi, I'm Mr. Hogan.

We're going to have such a great time learning Python programming together in this lesson.

I'm so pleased that you've decided to complete your learning with me today.

Shall we make a start? This is the first lesson from the Introduction to Python unit and is called Writing a Text-Based Programme.

By the end of today's lesson, you will be able to create a text-based programme from an algorithm that includes input and output.

As this is your first Python programming lesson, you might find it a bit tricky, but don't worry because I'm here to help you and we'll go through it step by step.

Here are the keywords from today's lesson: algorithm, programme, and syntax.

An algorithm is a sequence of steps that can be followed to do a task.

A programme is a set of commands that can be run by a computer in order for it to do a task.

And syntax is the precise way that a computer programme must be written to be understood by a computer.

There are three parts to today's lesson.

First, we'll describe how computers carry out algorithms. Then we'll look at how we can identify and correct syntax errors in programmes, and then we'll finish by writing and running our own Python programme that uses input and output.

Lucas here has switched on the TV but has no idea what to watch.

This algorithm has found TV programmes that Lucas might want to watch based on what he has watched in the past.

Have you ever switched on the TV and wondered where those recommendations come from? Can you think of any other algorithms that you come across in everyday life? An algorithm is a sequence of steps that can be followed to complete a task.

When a well-designed algorithm is followed, it leads to a task being completed.

Let's do a quick check for understanding.

An algorithm is designed to suggest a gift for Aisha's friend.

Which of the following would be most helpful for the algorithm to make a suggestion? You can pause this video at any time just to give you a little bit of time to think.

A: Aisha's friend's hobbies and interests.

B: What day Aisha's birthday is on, or C: the average price of birthday gifts.

That's right.

Aisha's friend's hobbies and interests would be most useful for the algorithm, because it could make suggestions about gifts that Aisha's friend would be most interested in.

An algorithm can be written and represented in many different ways.

Here's a flow chart which has been used to graphically represent an algorithm that checks if a passcode has been entered on a device correctly.

At the top, we can see the Start.

The user then enters the passcode, the algorithm checks if the passcode is equals to 1234.

If it is, it prints a "Welcome" sign.

If it's not, it goes back and asks for the passcode to be entered again.

A programme is a set of written commands in a programming language.

Computers run programmes in order for them to do tasks.

A programme is a way that computers can carry out the steps of an algorithm.

So you can see here in our original flow chart and now we have converted the flow chart into a computer programme.

This is the programme which is written in the programming language Python.

You'll be learning about Python all throughout this unit.

Let's do a check.

What needs to be created for a computer to carry out the actions of an algorithm? Remember, you can pause the video at any time.

Is it A: a flow chart, B: a command, or C: a programme? If you selected a programme, you are correct.

A computer needs a programme in order to be able to understand the actions of an algorithm.

Okay, let's have a look at the first task of today's lesson.

So tick the box in the table to match the definition to the word.

Remember, you can pause the video to complete the task.

We are now going to have a go at Task A part two.

Lucas here says, "We give computers algorithms to instruct them to carry out a task." Lucas is wrong.

Write a paragraph explaining why Lucas is wrong and make sure you use the keywords algorithm and programme from today's lesson.

Include examples of where Lucas may have seen algorithms in the world around us.

Pause the video again to complete the task.

Okay, let's go through the answers.

A set of commands that can be run by a computer in order for it to do a task is a programme.

Used to represent an algorithm graphically is a flow chart.

Remember that example we saw for the passcode earlier on in the lesson? A sequence of steps that can be followed to complete a task is an algorithm.

Lucas said that "We give computers algorithms to instruct them to carry out a task." Lucas is wrong because an algorithm is a sequence of steps that can be followed to complete a task.

A computer needs commands to follow in a programme in order to complete a task.

An algorithm must be first converted into a programme for the computer to follow.

People making social media applications design algorithms to show content they think will be of most interest to you.

They then make these work on the computers we use by creating programmes.

Have you ever scrolled through your social media and thought "That's strange, I was just looking at that."? Okay, we're now going to move on to the second part of today's lesson where we're going to be looking at identifying and correcting syntax errors in a programme.

Lucas and Aisha are having a conversation.

"Meet should we what time?" "O'clock five." What should Lucas and Aisha have said to each other? As humans, we can work out what Lucas and Aisha meant even though their words were jumbled up.

All languages have rules for syntax.

Speech or text in a language must follow its syntax so it can be understood.

For example, in different languages across the world, we'll greet and say hello to people in lots of different ways.

Humans can work out the meaning even when the syntax rules are not entirely followed as we've just seen.

However, computers cannot do this.

Programming languages also have rules for syntax.

They specify the way that the programme must be written in order for it to be understood by a computer.

And each programming language you come across will have its own unique rules for syntax.

Programmes written in a programming language must follow the syntax of that language so that it can be understood.

So what happens if a programme contains a syntax error? Programmes with syntax errors will not run correctly and will display an error message.

Let's do a quick check.

All programming languages have rules for.

Remember, you can pause the video at any time.

So is it gonna be A: spelling, B: translation, C: syntax? That's right.

Syntax.

Here are some Scratch blocks that you may have come across previously.

In a block-based programming language such as Scratch, syntax errors are not possible, as the rules are enforced by the blocks and the way they fit together.

In Python, it is easy to make syntax errors, and you will.

All programmers make syntax errors, even the most experienced programmers.

Syntax errors can be frustrating, especially when you start learning a text-based programming language like Python.

But don't worry, the more you come across, the more familiar you'll become and you'll find it easier to spot them.

In order to output or display information in Python, you'll need to use the print() function.

The print() function can be used to display text, number, characters from other parts of your programme.

Let's have a look at the syntax of the print() function.

We have the word print in all lowercase.

We open a bracket and then if we're displaying text or characters, we open speech marks.

We've then got the message we want to display, which is Hello world.

We close our speech marks and we close our brackets.

Let's do a check for understanding.

Identify the syntax error in this code.

You can pause the video at any time.

So what's missing? Is it A: bracket, B: print, or C: speech marks? That's right.

The second speech mark is missing.

Notice the colour highlighting of the second bracket, it's given us a clue that there's a problem.

That second bracket should actually be white, but it's showing as green.

Throughout this unit, we are going to be using the Raspberry Pi Code Editor, which lets you directly write Python code into your browser.

Starter code and practise tasks are available in the code editor to practise with your programming.

Let's watch the video and see how the code editor works.

<v Instructor>You can access the Raspberry Pi</v> Foundation Code Editor at editor.

raspberrypi.

org.

If you want to be able to save and download your files, you need a Raspberry Pi Foundation account and you can sign up and log in here.

Click Start Coding Python to begin.

The Raspberry Pi Foundation Code Editor will automatically load with a blank project.

The code editor has three main panels, the sidebar panel on the left, the code panel in the middle, and a preview panel on the right.

You can resize these panels using the handles.

The layout will adapt if you resize your browser window or if you're working on a device with a smaller screen.

The code editor offers accessibility features, which can be accessed in the settings menu.

You can switch between light and dark mode and then you can increase the text size.

The project bar is at the top and it shows the name of your project with an edit button, so you can change the project name, a button to download the project files and a link to log in if you haven't already done so.

Each project will automatically have a file called main.

py.

This is the code that will run for your project.

Let's have a look at some of the features of the code editor.

When you add new lines of code, line numbers will automatically be added for you.

Syntax highlighting improves the readability of your code by applying colours to different elements.

The code editor will automatically format your code with auto indentation.

Let's click Run and see the code in the preview panel.

<v ->Let's go onto Task B for the lesson.

</v> Identify the syntax error for the lines of Python code by completing the table.

Once you've done this, can you write the correct syntax for the code? Okay, Task B part three.

You're going to be provided with starter code which contains the first few lines from a well-known fairytale.

You need to find and correct the syntax errors in the code to make it display the lines of the story correctly.

If you have time, you could also go on and finish the story by creating more of your own print statements.

Okay, let's go back to Task B-1.

Did you spot all the syntax errors? The first line is missing a speech mark after world.

The second one, capital P instead of a lowercase P at the start of print.

And the last one is missing a bracket.

So therefore the correct code, which is in two, is the original print ("Hello world") statement that we've previously seen.

So to summarise Task B-3a, which is your starter code.

We've got a speech mark missing on line 1, a capital P is used for print on line 2.

It should be a lowercase P.

We've got another bracket missing on line 4, and then for the final two on line 5, we're missing a bracket and a speech mark.

You will now write and run a programme that uses input and output.

You have seen how to output information from a programme using the print() function.

You'll now see how a user can input data into a programme using the input() function.

This programme uses the input() function to take the name of the user, which is entered and then displays it back on screen as part of a sentence using the print() function.

The first line of code, the print statement is familiar to what we've seen already.

We've got a print() function, open brackets with some text inside some speech marks.

The second line, we've got the word user, which is a variable in this case, and we are making that equal to input().

Open bracket, close bracket for the function.

We've then got a third line of code which says print followed by our open brackets and some text which says Hello.

But then notice we've got a comma and the word user, which is our variable.

Shall we see what this will display if we run the code in the code editor? Here are the three lines of code in the editor.

Let's see what happens when we run the code.

So let's run line 1, so it's asking "What is your name?" So I'll put my name in.

So this will become the value that is stored in the user variable.

Oops, Matt.

Press enter, and then it runs line three, so it outputs "Hello" and the value that's held in the variable user, which in this case is Matt.

Okay, let's do a quick check for understanding.

What's the name of the function that can take information a user enters into a Python programme? Remember, you can pause the video at any point.

Is it A: output, B: print, or C: input? That's right, it's input because it's taking information into the programme.

If the user enters the name Aisha when prompted, this is what will be displayed on the code when the code is run.

If the user enters a different name, for example, Lucas, the output will change.

So whatever the user types for input(), it will take that, store it in the variable called user and then print it back out to the screen.

Let's do another quick check for understanding.

Which of the following pieces of code would output Hello followed by the name of the user which is entered? Look carefully at the code and have a think.

Remember, you can stop and pause this video at any point.

That's right, it's A.

It's not B because the user is assigned to the text Aisha in this example.

So it will always print "Hello Aisha" rather than the name of the user entered.

The third example takes the user's input, "Hello Aisha" but then it doesn't use it in the print statement.

It always prints "Hello Aisha" rather than "Hello," followed by the value that is held in the variable.

We're going to move on to Task C and you're going to write your own programme that uses input and output.

Write a programme that implements this algorithm.

Ask a user to input their name.

Ask the user to input their lucky number.

Print a welcome message and their lucky number.

The output from the programme should look like this.

Task C, part two.

Can you adapt your programme so the welcome message and lucky number are displayed on the same line? Okay, let's have a look at the solution.

You were asked to write a programme that asks a user to input their name and lucky number.

The programme should then print a welcome message and state their lucky number.

Your code should look something like this: a print() statement to ask what is their name, A variable called user, which is assigned to input().

Another print statement which asks what is their lucky number? A variable called lucky or number, which is equal to input().

And then a print statement which says "Welcome," followed by the user's name.

Another print statement which says, "Your lucky number is," followed by their lucky number.

Did you run your programme and come across any errors? Did you alter any of the syntax? You were then asked to adapt your programme so the welcome message and lucky number are displayed on the same line.

To do this, we just used our commas to concatenate or join together elements that we wanted.

So you'll notice on line 5 we have one print statement which says the text, "Welcome" surrounded by speech marks.

We then have a comma and the variable user.

We have another comma and the text, "Your lucky number is" and then we have another comma and the variable lucky, followed by our closed bracket.

Each time we want to join together text and a variable name in a print statement, we can use a comma.

We've come to the end of today's lesson and well done.

You've done a fantastic job at creating your very first Python programme.

We've seen that an algorithm is a sequence of steps that when followed, leads to a task being completed.

We've seen that all programming languages, including Python, have syntax rules, and a programme that contains a syntax error will not run.

We've encountered some common syntax errors, like forgetting to open and close brackets or speech marks or include in a capital letter in the statement.

A Python programme can take input using the input() function and output information using the print() function.

And you even created your own programmes that used input() and print() functions to take a person's name and display the message back to the screen.

Well done.

What a brilliant job!.