Karel Can't Turn Right - Python

Summary

This video tutorial introduces the concept of functions in programming, specifically for a character named Carol in a 'make a tower' exercise. It explains that Carol can't turn right with her basic commands, but the issue can be resolved by using functions to teach her new commands. The video demonstrates how to define a function in Python to make Carol turn right by turning left three times, emphasizing the importance of defining functions before calling them. It also shows how to implement the new 'turn right' function within the program to control Carol's movements effectively.

Takeaways

• 🤖 Carol, the robot, cannot turn right using the original four commands.
• 🔄 As a workaround, Carol can turn left three times to effectively face the same direction as if it had turned right.
• 📚 Introduction of functions as a way to teach Carol new commands beyond the initial set.
• 🔑 The term 'function' may also be known as 'procedure', 'task', or 'process', but in this context, it is primarily referred to as a function.
• 👨‍🏫 A function in Python is defined using 'def' (short for define), followed by the function name, parentheses, and a colon.
• 🔧 Indentation in Python is used to delineate the body of a function from the rest of the code.
• 🛑 Functions must be defined before they are called in a Python program; the program reads from top to bottom.
• 🔄 Demonstration of teaching Carol to turn right by defining a function that contains the sequence of 'turn left' commands.
• 📝 The function body includes the specific commands that make up the new 'turn right' command for Carol.
• 🔑 Calling the function 'turn right' in the code will execute the defined sequence of commands, enabling Carol to turn right.
• 🎓 Encouragement for the viewer to practice and experiment with functions in the programming editor.

Q & A

Why can't Carol turn right in the script?

Carol can't turn right because she only knows the original four commands and 'turn right' is not one of them.

What is the alternative method to make Carol face East if she can't turn right?

The alternative method is to make Carol turn left three times, which results in her facing East.

What is a function in the context of the script?

A function is a way to teach Carol new commands or words, breaking away from the original four commands she knew.

What is the purpose of teaching Carol new commands with functions?

The purpose is to expand Carol's capabilities beyond the original commands, allowing her to perform more complex tasks.

What does 'def' stand for in the script?

'def' stands for 'define', which is used to start the definition of a new function in Python.

How does Python use indentation to delineate code?

Python uses indentation to indicate the start and end of a block of code, such as the body of a function.

Why is it necessary to define a function before calling it in Python?

In Python, functions must be defined before they are called because Python reads from the top down, and it needs to know what the function does before it is executed.

What is the error that occurs if you try to call a function that hasn't been defined yet in Python?

An error will occur stating that the function is not defined, with a reference to the line number where the call was made.

How does the script demonstrate teaching Carol a new command?

The script demonstrates it by defining a function called 'turn right' and then calling that function to make Carol execute the new command.

What is the significance of the 'make a tower' exercise in the script?

The 'make a tower' exercise is used as a practical example to illustrate how to teach Carol new commands using functions.

How does the script suggest to fix the issue of Carol not being able to turn right?

The script suggests creating a function named 'turn right' that contains the sequence of commands to turn left three times, effectively turning right.

Outlines

00:00

🤖 Teaching Carol New Commands with Functions

The video introduces the concept of functions as a method to teach Carol, a robot, new commands beyond her original four. The issue of Carol's inability to turn right is highlighted, and a workaround of turning left three times is discussed. The main focus is on defining a function in Python to enable Carol to turn right. The process involves using the 'def' keyword, giving the function a name, and using indentation to define the function's body, which in this case includes three 'turn left' commands to achieve a right turn. The video emphasizes the importance of defining functions before using them in Python due to its top-down reading order, and demonstrates how to integrate the new 'turn right' function into Carol's existing code.

05:01

📝 Implementing the TURN RIGHT Function in Python

This paragraph continues the discussion on functions by demonstrating how to implement the newly defined 'turn right' function in Carol's code. It explains the importance of proper indentation in Python to distinguish between the function body and the rest of the code. The video shows a practical example of modifying Carol's code to include the 'turn right' function, ensuring it is placed at the top as per Python's requirement. The demonstration includes running the code to check if the function works correctly and adjusting the code to call the 'turn right' function, resulting in Carol successfully turning right. The viewer is then encouraged to practice using functions in the Python editor.

Keywords

💡Carol

Carol is a hypothetical robot in the context of the video, which is used to illustrate programming concepts. The name 'Carol' is likely a stand-in for any robot that the viewer might be programming. In the video, Carol is unable to perform certain actions, like turning right, without being explicitly programmed to do so, which is a central point in the discussion of how to expand her capabilities through functions.

💡Commands

Commands in this video refer to the basic instructions that Carol, the robot, can initially understand and execute. The script mentions that Carol only knows 'those original four commands,' which are presumably the most basic actions she can perform, such as moving forward or turning left. The concept is integral to understanding the limitations that the video aims to overcome with the introduction of functions.

💡Turn Right

The phrase 'turn right' is a command that Carol cannot initially execute. The video script discusses the issue of Carol's inability to turn right and how it can be circumvented by turning left three times. The concept of 'turn right' becomes a problem that the video seeks to solve through the introduction of functions, making it a pivotal point in the narrative.

💡Functions

Functions are introduced in the video as a way to teach Carol new commands beyond her original capabilities. The term is used to describe a block of code that can be defined once and then called multiple times, which is a fundamental concept in programming. In the context of the video, functions are used to define a new command for Carol to turn right, thus expanding her abilities.

💡Define

The term 'define' is used in the context of creating a function in programming. In the video, 'def' is short for 'define' and is used to start the declaration of a new function, such as 'turn right'. This keyword is crucial as it marks the beginning of the process of teaching Carol a new command through programming.

💡Indentation

Indentation in the video refers to the use of whitespace at the beginning of a line of code to indicate a block of code that is part of a function. The script explains that commands within a function must be indented to be recognized as part of that function's body, which is a key aspect of Python syntax highlighted in the video.

💡Order of Functions

The 'order of functions' is a concept discussed in the video that highlights the importance of defining a function before it is called in Python. The video script mentions that Python reads from the top down, and if it encounters a function call before the function's definition, it will produce an error. This is a specific Python programming concept that is essential for understanding the correct structure of code.

💡Make a Tower Exercise

The 'make a tower exercise' is a specific programming task mentioned in the video that involves Carol placing balls to form a tower structure. The exercise serves as a practical scenario where the limitations of Carol's original commands become apparent, and the need for functions to expand her capabilities is demonstrated.

💡Turn Left

The term 'turn left' is used in the video to describe one of the original commands that Carol can execute. It is also used to illustrate the workaround for Carol's inability to turn right by turning left three times. This command is fundamental to the workaround solution and the subsequent discussion of how to improve it with functions.

💡Call a Function

Calling a function in the video refers to the act of executing a block of code that has been previously defined as a function. The script explains that once a function like 'turn right' is defined, it can be called by simply using its name, which instructs Carol to execute the sequence of commands within that function. This is a key concept in demonstrating how functions can be used to control Carol's actions.

Highlights

Carol, the robot, cannot turn right using its original commands.

A workaround for Carol's inability to turn right is to turn left three times.

Functions are introduced as a method to teach Carol new commands.

Functions can also be called procedures, tasks, or processes.

The 'def' keyword is used to define a new function in Python.

Indentation is crucial in Python to delineate the function body.

Functions must be defined before they can be called in Python.

The order of function definitions matters in Python due to its top-down reading.

A practical example of teaching Carol to turn right using a function is given.

The 'turn right' command is created by defining a function with three 'turn left' commands.

Executing a function in Python requires calling it after its definition.

An error occurs if a function is called before it is defined in Python.

The video demonstrates using the 'turn right' function in a Karel programming exercise.

The 'put ball' and 'move' commands are used in the Karel exercise.

The video shows a step-by-step process of teaching Carol a new command through functions.

The importance of correctly indenting commands within a function is emphasized.

The video concludes with Carol successfully turning right using the newly defined function.

The video encourages viewers to experiment with functions in the Karel editor.

Transcripts

hi in this video we're going to talk

about something that you may have

already noticed and that is Carol can't

turn right so let's think back to the

make a tower exercise so you may have

gotten to a point in the program where

you got Carol to the top of the tower

and you wanted Carol to turn right to

face East you may have even typed out

turn right and you probably found out

that it did not work

Carol cannot turn right Carol only knows

those original four commands so instead

what can we do you've probably

discovered that instead of turning right

we can turn left three times and achieve

the same results Carol will go from

north through west south and then

finally end up facing east so Carol will

pretty much turn right but that's not

really the best way to do it would it be

nice if we could just say turn right

that is really what we want Cara to do

we don't want Carol to have to turn left

three times so how can we do that

introducing functions functions are a

way we can teach Carol new words so what

is a function it's a way to teach Carol

new words and break away from the

original four commands that we had to

start with and we can teach Carol a new

command

you might hear functions called

different things such as procedures

tasks processes but in this course we're

mainly going to call them functions we

want to teach Carol how to turn right so

how do we do that

this is how we teach Carol to turn right

we write def short for define and then

we give the function a name open and

close parentheses in a colon then for

every command that we want to be a part

of the function we write it indented by

one tab or one level in Python we use

indentation to help delineate our code

so the function body would contain these

three commands to turn left once we stop

indenting the commands are no longer a

part of the function so in this case the

move command would not be part of our

function

one thing that is different about Python

compared to other languages is that the

order that we put our function in

matters in Python we must define a

function before we can call it when we

go to execute our programs Python reads

from the top down and if it gets to the

command to turn right but hasn't seen

the definition to turn right yet it'll

produce an error so let's take a look at

how we use functions and how we can

teach Karel new commands in the editor

okay so let's take a look at how we can

use this make a tower with a turn write

command so if you think back to what we

did we probably started off with a move

command and then we would have said turn

left let me go back and check this so

far you can see okay we've done that now

we need to put a ball down we're gonna

say put ball and then move okay let's go

check that again okay so we're off to a

good start let's continue from here so

now we want to we want to put another

ball then we're going to move put ball

and move let's run that right there

we're going to reset and run okay so now

we're at the top of our pyramid we're

close to having the the result world

here but we need to do is if we look at

our exercise we need to have Karel

facing east and right now Cairo is

facing north so what we want to try is

something like turn right and if we do

that and we go to run we're gonna see

uh-oh

turn right is not defined on line 9 so

if you remember we probably to solve

this said let's go and turn left three

times

and that would solve it for us so let's

go ahead and reset and then we'll try

running that so there it goes Carol up

the tower turns left and nice job we got

it okay so now what we want to do though

is we want to make that turn right

command so now remember in Python we got

to put that command up top here and so

we're going to make a function and we're

going to teach Carol a new word and

we're going to teach Cairo that TURN

RIGHT command so we start off with def

for define and then we're gonna say turn

right so we're gonna teach Carol how to

turn right okay now our format in Python

we put a colon after our definition and

now notice how we start off indenting a

line there so now we want to take these

three commands and we're going to take

them and put them up in Arkham in there

so no matter make sure that we are

indenting all the same

remember our code that's indented as

part of our function and our code that's

not indented is not part of our function

so all these commands will not be part

of our function all of these are so if I

go ahead and reset you'll notice the

program just really skips over that turn

right and it comes up and we haven't

turned right yet because we've only told

Carol how to do that command we haven't

actually asked Carol to do it so we're

going to go down here and now we're

going to ask Carol to turn right okay so

we're going to go back and reset that

now that we're calling our function it

should execute these commands and you'll

notice as it goes and executes the

commands this line that's showing where

we're executing is going to jump up into

that function and come down and run the

lines and there we go we've now talked

Carol how to turn right so now it's your

turn to play around in the editor