Welcome to Python! Ilhoe Jung. Graphics & Media Lab

Transcription

1 Welcome to Python! Ilhoe Jung Graphics & Media Lab

2 Course schedule [Lecture 1] Introduction & Basic Grammar [Lecture 2] Data type & Class [Lecture 3] External libraries for python

3 Introducing Python! Graphics & Media Lab

4 Introduction Designed by Guido van Rossum Named after his favorite TV-show

5 Introduction Open source Platform independent Object-oriented Interpreted

6 Why Python? It s easy Syntax is very simple, and many good tutorials and documents are available. You can do everything Python itself is amazingly powerful. There are large collection of libraries for almost every kinds of applications you can imagine Everyone uses it! Google s four major languages: C++, Java, JavaScript, and Python.

7 The social network

8 Python 2 or 3? What is the difference? Slight changes in grammar String Unfortunately, we re in the middle of the big transition Python 3.3 is the most state-of-the-art version of Python Python 2.x is still the most dominant version of Python in the industry Which version should I install, then? Just install Python 3.3 in this lecture.

9 Install Python

10 Run IDLE

11 Run IDLE

12 What is IDLE? Integrated Development Environment (IDE) for Python Multi-window text editor with syntax highlighting, smart indent and other. Python shell with syntax highlighting IDEs for other languages Visual Studio (C, C++, C#,...) Xcode (C, C++, Objective-C, Java,...) Eclipse (Mostly for Java) And many others!

13 Hello, World! C #include <stdio.h> C++ #include <iostream> int main(void) { printf("hello world\n"); return 0; } PHP <?php echo "Hello World!";?> Java public class HelloWorld { public static void main(string[] args) { System.out.println("Hello world!"); } } Visual Basic.NET Module Module1 Sub Main() Console.WriteLine("Hello, world!") Console.ReadKey() End Sub End Module int main() { std::cout << "Hello World!" << std::endl; return 0; } Action Script 3.0 package com.example { import flash.text.textfield; import flash.display.sprite; } public class Greeter extends Sprite { public function Greeter() { var txthello:textfield = new TextField(); txthello.text = "Hello World"; addchild(txthello); } }

14 Hello, World! In python, just one line.

15 Using.py file

16 Run.py file Save file as hello_world.py

17 Run.py file Click Run menu -> Run Module or Just input F5

18 Basic Grammar Graphics & Media Lab

19 Type, variable Operator Function Condition Iteration

20 Type Types in python Python has the similar types with other languages.

21 Types in Python Python 2 Python 3 types.unicodetype str types.stringtype bytes types.dicttype dict types.inttype int types.longtype int types.listtype list types.nonetype type(none) types.booleantype bool types.buffertype memoryview types.classtype type types.complextype complex types.ellipsistype type(ellipsis) types.floattype float types.objecttype object types.notimplementedtype type(notimplemented) types.slicetype slice types.tupletype tuple types.typetype type types.xrangetype range

22 Instance What is instance? Type defines what it is. Instance is realization of type

23 Variable Variable declaration C++ Python No type of the variable!

24 Rules of variable name They are case-sensitive! Also, it is illegal to use:

25 Rules of variable name You cannot use Python keywords for the name of the variable.

26 Operator Almost same with C++

27 Operator Example

28 String operator String addition String Multiplication

29 Logical operator is, not Semi-colon for line breaker

30 Logical operator and, or In c++, same with &&,

31 Function Function definition Function Name Input Parameters Return value Python use indentation to separate codes. No types of parameter or return.

32 Function Using function

33 Condition Execution

34 Condition Execution if

35 Condition Execution Chained condition

36 Function and Condition

37 Recursive Function Call

38 Exercise Implement a function factorial(n) using recursive call. factorial(5) = 5! = 5*4*3*2*1 = 120

39 Iteration

40 Iteration While

41 Tips Does Python have ++/-- operator? Nope Why? Many reasons, but most of all, ++ and -- can bring unne cessary pain. Also, Guido (the inventor) didn t like them :D I tried ++i and --i, but the program did executed anyway. What happened? Python will interpret ++i as +(+i), and same for --i = -(-i).

42 Iteration Break

43 Iteration Continue

44 Iteration for

45 Iteration range() is a function, which generates series of values. range(5): 0, 1, 2, 3, 4 range(2,6): 2, 3, 4, 5 range(1,6,2): 1, 3, 5 range(100,0,-30): 100, 70, 40, 10

46 Exercise Implement a function factorial(n) using iteration.

47 Exercise Implement NewtonMethod(f,f2,start,iterNum) For a function f(x), we want to find x, which satisfies f(x) = 0. f x = x 2 start = 5, iterate N = 30

48 User Input

49 Comments One line comment Multiline comment

50 What we learn so far Type, variable Operator Function Condition Iteration