Numbers

In this and the following section we examine three new types of objects

Type	Used for	Examples
Integers	Numbers	-5 16
Floats	Decimal	3.4 -23.001
Strings	Text	‘abc’ ‘bob’

We will look at how to create objects of these types and what operators (behaviours) they respond to.

Integers & Floats

int objects represent natural numbers. float objects represent rational numbers, numbers that have a decimal value. Both types can represent positive or negative numbers.

Creation

Unlike creating turtles there is no formality to creating an int and float objects.

You just type them as literals:

>>> 3
3
>>> type(-5)        # confirm type
int
>>> 3.4
3.4
>>> type(3.0)
<class 'float'>

Questions

1. Why do we have two different types to represent numbers?
2. Find some uses cases where you’d choose an int and others where a float is more suitable.

Number Operators

Tip

Unlike turtle object methods, we use operators to manipulate number objects. This special syntax exists as it maps to our expectations and so is more intuitive.

Arithemtic operators

Two number objects separated by an arithmetic operator * / - +, actions behaviour we expect from basic arithmentic.

>>> 5 + 4
9
>>> 5 - 6
-1

The behaviour is to compute and return the result as a new object with the same type.

Comparison operators

Likewise two number objects separated by comparison operators == != >= <= < >, have the behaviour we expect.

>>> 5 == 4
False                # What is this?
>>> 5 < 6
True                 # and this?
>>> 6 <= 6
True

Tip

int objects are used to solve problems that require manipulating numbers but with no decimal point such as age, and days, IDs.

These are expressions and these evaluate to True or False.

The if conditional

This pattern:

if <boolean expression>:
    <block of code>            # Note 4 space indent

mirrors the syntax required to define conditional behaviour.

Typically we use the result of comparison statements to make decisions on what code to execute.:

if 6 > 5:
    print('Greater Than')

if statements can combine with else:

if 6 > 5:
    print('Greater Than')
else:
    print('Not Greater Than')

Questions

Find some uses cases where you’d use the if conditional.

Number Exercises

1. A bar wants to ensure only adults are allowed in. Write a program in a file named bar.py that prints ‘underaged’ or ‘ok’ depending on the age entered in the code.
2. A ride operator needs to ensure clients are taller than 150cm due to security. Write a prgram in a file named ride.py that will print ‘ok’ or ‘not tall enough’ given a height entered in the code.
3. A trader wants to algorithmically buy ‘ACME` corp stock if they rise above 0.005$ but sell if they are below 0.001$. Write a script trader.py that prints ‘buy’, ‘sell’, ‘hold’ depending on a sale price entered in the script.