1. Understanding Variables
Python
Understanding Variables

2. Variables What is a variable? Definition
A named area of storage in a computer program that can change as the program runs

3. Are all numbers the same?
Content of Variables
Words and letters
These are known as strings
Numbers
Boolean
Are all numbers the same?

4. Working with variables
The type of information stored in a variable is referred to as its datatype
The datatype controls how the program will process the data
Eg Arithmetic can’t be performed on strings
Numbers can only contain 0-9 and . –
Special functions convert between strings and numbers – This is called Casting

5. Casting a Numeric Variable
Numbers typed into Python arrive as a string
They must be converted to a number before using in arithmetic
number1
“29” 29
number1
number1
“29”

6. Variable Names
A Variable name MUST start with a letter or an underscore NOT a number.
Numbers can be included within the name, but not as the first character.
A Variable name can be any length but is best to keep it reasonably short.
Must consist of a continuous string of characters. That means they CANNOT have any spaces.
Identify words by either capitalising the first letter of each word, or by using the underscore character.
firstName
first_name
Only in exceptional circumstances use single letters for variable names
Should be meaningful - describe the data they contain