Computer Science

Computer Science

1. Python

   • Python is simple to learn
   • Used By:
     • Nokia
     • NASA
     • Paint Shop Pro
     • Google's Search Engine
     • Civillisation 4 Computer Game
     • CERN Large Hadron Collider Research
   • Python's Development Environment
     • Called IDLE - Intergrated Development Environment
     • Two Modes
       • Interactive Mode
         • Lets you see your results as you type them
       • Script Mode
         • Lets you save your program and run it again later
   • De-Bugging
     • Syntax Errors
       • Reading interpreter feedback
     • Bugs
       • The name "Bug" refers to an error in a program
   • Variables
     • A variable is a location in memory in which you can temporarily store text or numbers
     • You can choose a name for the variable and change its contents for the program
     • A variable name can contain only numbers, letters and underscores
     • A variable name cannot start with a number
       • You can’t use a Python “reserved word” as a variable name – for example class is a reserved word so class = input() will result in a syntax error
   • Adding comments
     • Comments are useful to help understand your code
     • They will not affect the way a program runs
     • Comments have a preceding # symbol
   • Functions
     • Functions are special keywords that do a specific job
     • print() and input() are examples of functions

2. Numbers and Arithmetic

   • Data types
     • Strings
       • Holds alphanumeric data as text
     • Interger
       • Holds whole numbers
     • Float
       • Holds numbers with a decimal point
     • Boolean
       • Holds either True or False
   • Python automatically assigns a data type to a variable
   • You can override this to manually define or change the data type using:
     • str()
     • int()
     • float()
   • Assignment statements
     • Assignment statements assign a value to a variable. If the variable doesn’t already exist, it’s created.

3. Selection

   • Indentation
     • Python requires indentation as part of the syntax
     • Indentation signifies the start and end of a block of code
     • Programs will not run without correct indentation
   • Using an IF statement
     • An IF Statement uses Selection
     • IF forces a decision
     • If condition Then do this Else do that
   • The ELIF statement
     • If gives you two options
     • ELIF stands for Else, If and gives you more options
     • You can use it as many times as you like