Think Python

Think Python

1. Green Tea Press Chapter 1

   • 1.1
     • Interpreters and Compilers
       • These are both ways of translating High level languages into lower level ones
         • A compiler checks and translates the whole of the source code before running the program
         • An interpreter translates and executes the souce code a chunk at a time. It translates a line then runs it
           • Example
             • Python is an iterpreted language because it is executed by an interpreter
               • There are two ways to use this interpreter: Interactive mode and Script mode. Interactive mode is on the initail window marked by >>> which is a direct way to execute code >>> 2+2 and python will respond on the next line with >>> 4 . Script mode needs a new window opened and is used for larger and more demanding scripts like a full game or etcha-sketch
     • High Level and low level programs
       • Higher level programs are able to work on a variety of computers with very little tweaking
         • Python is a high level program so the computer has to go through it before it runs. Other examples are Java and C++
       • Low level programs don't need translating
   • 1.2
     • What is a program?
       • A program is a set of instructions that says how to perform a computation
         • The details vary per specific language but same basic principals remain. These are what a program is translated into, it doesn't matter how complicated it may be
           • Input: Gathering data from a keyboard, mic or other device
           • Output: Displaying the data on a screen or other device
           • Math: Simple addition, subtraction etc
           • Conditional execution: Looking for the IFs and BUTs within a program and following them
           • Repetition: Repeating an action. sometimes with slight variations
   • 1.3
     • Debugging
       • Debugging is the process of finding and correcting errors in you program
         • There are 3 types of error
           • Syntax Error
             • A syntax error is an error with the rules of a structure: (2+2) is legal, but 2+2) is not because brackets always come in pairs
           • Runtime Error
             • Runtime error is an error that occurs after the program has started running
           • Semantic Error
             • A semantic error is not a problem with how you composed the program's structure it is a problem with what you wanted the program to do: so you wanted to print "Hello" but you typed print "Helo" instead that would be a semantic error
   • 1.4
     • Language types
       • Formal
         • These were created to express a point in a clear and easily understood way
           • Examples of this are mathematical notation and chemical short hand
             • Maths has basic syntax rules: 2+2 = 4 is correct but 3+=4(0 isn't
             • Chemical short hand also has basic syntax rules: CO is the short hand for carbon monoxide but Zz doesn't work as there is no element with the short hand of Zz
       • Natural
         • These are languages like English, German and French, they have evolved over time, they were NOT created over night or by one specific person
   • 1.5
     • The first program
       • The traditional first program you should write is, in python: print "Hello, World" , this is a print statement meaning it will show Hello, World on the screen. the " in the program defines what will be displayed and the print is the output method
   • 1.6
     • Treating the computer right
       • Many people treat a computer as though it was a real person, getting angry at it when it points out the smallest fault and viewing it as a teammate when it all seems to be going well.
         • The best way to view a computer is to see it as a fellow student that has certain strengths and weaknesses: it is efficient, fast and hard working but it is pedantic and narrow minded. try to use the advantages and work around the weaknesses to get the best from your computer