Touring Turing

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1 What is 'Conditional Selection'

Learn It

One of the important aspects of a Turing machine, is the ability to change the tape, depending on what was written on some programmed cards.
So, for instance, if the Turing machine was at box 500 on the tape, if the symbol written there was a 1 - it would leave it and move to the next box. else if the symbol that was written there was a 0 the erase it and write in a 1, before moving on to the next box.

Learn It

This is know as Conditional Selection.
If you want to imagine using Conditional Selection in real life, think about a simple decision you might make before leaving the house in the morning.

If it is cold I will take my coat, else I'll leave it at home.

Code It

Let's try and code the above example using python.
Open IDLE and create a new script (Ctrl+n) called coat.py
We need to start by creating a variable to store whether it is cold or not.
On the first line of your script write the following line.

coldOutside = True

True is a type of data in Python.
Now we're going to start our conditional selection. Write this line next.

if coldOutside == True:

The double equals is known as a test for equality. In Python a single equals is used for assigning variables. A double equals tests if two things are the same.
The : is important. It tells the computer that we have finished stating the condition. In this case that coldOutside = True
Now hit Enter on your keyboard and stop.

The cursor has automatically been placed 4 spaces in, leaving what is known as significant whitespace where you are going to write your next line.
If you accidentally delete the whitespace (do it now), you can add it back in by using the Tab key on your keyboard.

Let's write the next line

if coldOutside == True:
    print('You had better take your coat')

Because the print() statement is written after the significant white space, it will only be executed if the line above it is True.
What happens if coldOutside isn't True?
We need to prepare for that as well.

if coldOutside == True:
    print('You had better take your coat')
else:
    print('Leave your coat at home')

Notice that the else: has no whitespace before it.
The print() statement under the else: condition, only runs if coldOutside is not True
Ctrl+s and then F5 to save and run your script.
Now try changing the variable coldOutside from True to False

Badge It - Silver

Now it's your turn to write some conditional selection scripts. Make sure you use sensible variable names
Try the following:
1. Write a script that prints out whether you should have a snack based on whether you are hungry or not.
2. Write a script that prints out whether you should have a sleep or not based on whether you are tired or not.
3. Write a script that prints out whether you should take a bus or not based on whether your journey is a long one.

2 More tests

Learn It

We can use conditional selection to test for pretty much anything, not just whether a variable is True or False.
We can test the value of any variable value we like.

Code It

Let's make a little chatbot.

name = 'Alice'
if name == 'Alice':
    print('Nice to meet you ' + name)
else:
    print('I wanted to speak to Alice, not ' + name)

We can make this script a little more interactive by using input() like we did in the previous lesson

name = input('Hi, what is your name? ')
if name == 'Alice':
    print('Nice to meet you ' + name)
else:
    print('I wanted to speak to Alice, not ' + name)

You can change what the script replies if you like.
Let's extend it a little. Add a second block of conditional selection to your script, underneath the first.

pets = input('Do you have any pets? ')
if pets == 'yes':
    print("That's nice. I love pets")
else:
    print("That's a shame. You should buy a dog.")

Add a few more questions and responses of your own, to extend the chatbot.

Badge It - Gold

We can use Conditional Selection to make a quiz.
Have a look at the script below.

score = 0

userAnswer1 = input('What is the capital city of England?' )
if userAnswer1 == 'London':
    print('Correct')
    score = score + 1
else:
    print('Incorrect')

The first line creates a variable called score and sets it to 0
This line

score = score + 1

adds 1 to the score. As it has whitespace before it, it only runs when the user gets the answer correct.
Add 4 more questions to your script.

3 Type Casting again

Learn It

It would be nice if we could print out the score at the end of the quiz.
There's a slight problem though.
Try this as the last line of code.

print('You scored ' + score)

Run through the quiz and see what happens.
The problem is the same as we experienced in the last lesson. The string 'You scored ' and the integer score are different types, and you can't concatenate different types in Python (Do you still remember what concatenate means).
This time we'll use the inbuilt function str().
This converts numbers to strings. So if the score was 6 it would convert it to '6'
Change your last line of code so it looks like the one below.

print('You scored ' + str(score))

Code It

Can you remember how to use int() to change a user's input into a number.
We could add some Maths questions to our script by using int()
Here's an example question, and the beauty of it is that we don't have to work out the answer ourselves.

answer6 = int(input('What is 7 multiplied by 8? '))
if answer6 == 7*8:
    print('Correct')
    score = score + 1
else:
    print('Incorrect')

Badge It - Platinum

Now try adding 3 simple Maths questions to the quiz (addition, multiplication, subtraction or division (+,*,-,/))
Add another question 3 questions that asks the user to answer the same questions you answered for the The Platinum Badge on Week 1