Think Python

Think Python

Green Tea Press Chapter 1
1. 1.1
  1. Interpreters and Compilers
    1. These are both ways of translating High level languages into lower level ones
      1. A compiler checks and translates the whole of the source code before running the program
      2. 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
  2. High Level and low level programs
    1. Higher level programs are able to work on a variety of computers with very little tweaking
      1. Python is a high level program so the computer has to go through it before it runs. Other examples are Java and C++
    2. Low level programs don't need translating
2. 1.2
  1. What is a program?
    1. A program is a set of instructions that says how to perform a computation
      1. 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
3. 1.3
  1. Debugging
    1. Debugging is the process of finding and correcting errors in you program
      1. 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
4. 1.4
  1. Language types
    1. Formal
      1. 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
    2. Natural
      1. These are languages like English, German and French, they have evolved over time, they were NOT created over night or by one specific person
5. 1.5
  1. The first program
    1. 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
6. 1.6
  1. Treating the computer right
    1. 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.
      1. 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

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