Intro Python Y9

Intro Python Y9

Mr. Williams

​Examples of Variables

​The following are examples of ACCEPTABLE variable names:

​

• ​apples, car, costs

• b8, a12, z1000

​

​The following are example of NOT ACCEPTABLE variable names:

​

• ​1, 100, 3000, 22, 14 (a variable can not start with a number)

• ​print, input, def (these are keywords used within python)

​Variables

​Part of a program that can be assigned a specific value

​

• ​Made up of two parts; an identifier, and a value.

• ​This value CAN change while the program is running.

​Constant

​Part of a program that can be assigned a specific value

​

• ​Made up of two parts; an identifier and a value.

• ​This value can NOT change while the program is running.

Multiple Choice

What is the name of the 'Variable' in this example Python code

• name

• input

• print

• ("What is your name")

​Commenting your code

​It's important to comment your code often.

​

​When commenting code, use the symbol # followed by your comment

Multiple Select

Why is it important that we use comments in our code?

• They help the program run smoothly

• So that we understand what the line of code does

• To help other programmers understand our code

• To fill our code with colours

​Variable names

​Variable names are limited to certain characters when they are defined in your code. Using incorrect Variable names will result in your code displaying the error:

​

​"Syntax Error: invalid syntax"

Multiple Select

Which of the following are acceptable Variable names

• horse

• x

• 3

• x4

​Variable Types

All data in Python is represented by 'objects' or the relationship between 'objects'.

​

​Every object has three things:

• ​An 'identity'

• ​A 'type'

• ​A 'Value'

​

​An objects 'identity' never changes once it has been created - it is forever saved in the Python's memory.

​Variable Types continued..

An object's type determines what operations that it supports, for example:

• ​Does it have a length? which then defines the possible values for objects of that type.

​

​The type() function returns an object's type (which is an object itself)

​Just like an object's 'identity', an object's type is also unchangeable.

​

The values of some objects can change though...

Multiple Choice

Objects who value is unchangeable once they are created are called...

• Immutable

• Mutable

• Defined

• Undefined

Multiple Choice

When this Python code is run what will it display?

• <class = 'int'>

• <class = 'float'>

• <class = 'int'>

  <class = 'float'>

• 9

  9.0

Type conversion​

​There are several built-in functions that let you convert one data type into another. These functions return a new object representing the converted value, such as:

​

• ​int(x) which converts x into an integer

• ​float(x) which converts x into a floating-point number

• ​str(x) which converts x into a string representation

Multiple Choice

What would you type to covert the float number to an integer?

• print(type(float_number)

• print(float_number)

• print(int(float_number)

• print(number)