Outline. Simple types in Python Collections Processing collections Strings Tips. 1 On Python language. 2 How to use Python. 3 Syntax of Python

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1 Outline 1 On Python language Marcin Młotkowski Object oriented programming 1 / 52

2 On Python language The beginnings of Pythons 90 CWI Amsterdam, Guido van Rossum Marcin Młotkowski Object oriented programming 2 / 52

3 Current state Python Software Foundation (PSF) Marcin Młotkowski Object oriented programming 3 / 52

4 Current version 2.* (2.4, 2.6, 2.7.2) 3.* (3.2.2) Marcin Młotkowski Object oriented programming 4 / 52

5 Why I like Python On Python language Simple and clean syntax: factorial few keywords and operators; indentation is obligatory def fact(x): if x == 0: return 1 else : return x * fact(x-1) Marcin Młotkowski Object oriented programming 5 / 52

6 Why Python is so cool Styles of programming structural programming object oriented programming functional programming Marcin Młotkowski Object oriented programming 6 / 52

7 Why Python is so cool Built-in types Lists vec = [1, 2, 3] doubled_vec = [ 2*e for e in vec] Dictionaries phone = { chris : , Susie : } print tel[ susie ] Marcin Młotkowski Object oriented programming 7 / 52

8 Why Python is so cool Batteries included I/O libraries regular expressions HTTP, HTML, XML GUIs: pygtk, wxpython, Tkinter, PythonWin Marcin Młotkowski Object oriented programming 8 / 52

9 Other features of Python Dynamic type system >>> 2 + "two" Traceback (most recent call last): File "<stdin>", line 1, in? TypeError: unsupported operand type(s) for +: int and str >>> Marcin Młotkowski Object oriented programming 9 / 52

10 Applications of Python Projects System tools (RedHat) Google NASA ZOPE/PLONE Marcin Młotkowski Object oriented programming 10 / 52

11 Outline 1 On Python language Marcin Młotkowski Object oriented programming 11 / 52

12 Interactive mode $ python >>> >>> [1,2,3][-1:] [3] Ctrl-d $ Marcin Młotkowski Object oriented programming 12 / 52

13 Execute a file $ python a_file.py What s happened 1 program compilation (inc. syntax checking) Marcin Młotkowski Object oriented programming 13 / 52

14 Execute a file $ python a_file.py What s happened 1 program compilation (inc. syntax checking) 2 sometimes a file *.pyc is created Marcin Młotkowski Object oriented programming 13 / 52

15 Execute a file $ python a_file.py What s happened 1 program compilation (inc. syntax checking) 2 sometimes a file *.pyc is created 3 execute a program Marcin Młotkowski Object oriented programming 13 / 52

16 Outline 1 On Python language Marcin Młotkowski Object oriented programming 14 / 52

17 Syntax Assignment four = x = y = z = 0 name = Pyt + hon primes = [2, 3, 5, 7] a, b = b, a+b Marcin Młotkowski Object oriented programming 15 / 52

18 Syntax Conditional statement x = 4 if x % 2 == 0: print "even" print "x = ", 2 x = 4 if x % 2 == 0: print "even" print "x = ", 2 Marcin Młotkowski Object oriented programming 16 / 52

19 Syntax Conditional statement x = 400 if x % 2 == 0: if x > 100: print "large even" elif 10 < x <= 100: print "small even" else: print "tiny even" Marcin Młotkowski Object oriented programming 17 / 52

20 Logic expressions On Python language false: 0, False, None, [], Marcin Młotkowski Object oriented programming 18 / 52

21 Logic expressions On Python language false: 0, False, None, [], true: True, nonempty values Marcin Młotkowski Object oriented programming 18 / 52

22 Logic expressions On Python language false: 0, False, None, [], true: True, nonempty values conjunctions: and, or, not Marcin Młotkowski Object oriented programming 18 / 52

23 Logic expressions On Python language false: 0, False, None, [], true: True, nonempty values conjunctions: and, or, not operators: ==,!=, 1 < x < 2 Marcin Młotkowski Object oriented programming 18 / 52

24 Loop statement A statement while a, b = 0, 1 while b < 10: print b a, b = b, a + b Marcin Młotkowski Object oriented programming 19 / 52

25 Loop statement for in a = [1,2,3,4] for e in a: print e print "end" Marcin Młotkowski Object oriented programming 20 / 52

26 Loop statements On Python language for in sum = 0 for i in range(100): sum = sum + i print "sum=", sum Marcin Młotkowski Object oriented programming 21 / 52

27 Other statements On Python language break and continue empty statement: pass while (True): pass Marcin Młotkowski Object oriented programming 22 / 52

28 Functions def foo(arg1, arg2=1, arg3=[3]): print arg1, arg2, arg3 return 4 foo("one", 2) print foo(1, 2, 3) Marcin Młotkowski Object oriented programming 23 / 52

29 Comments def fun (arg): """ This is very important function Use with high esteem""" # end if empty argument if arg == None: return return arg Marcin Młotkowski Object oriented programming 24 / 52

30 Input/output Python 2.* print "Hello world" x = input("type x: ") y = input("type y: ") print "x =", x, " y =", y Marcin Młotkowski Object oriented programming 25 / 52

31 Input/output Python 2.* print "Hello world" x = input("type x: ") y = input("type y: ") print "x =", x, " y =", y Python 3.0 print("hello world") x = input("type x: ") y = input("type y: ") print("x =", x, " y =", y) Marcin Młotkowski Object oriented programming 25 / 52

32 Editors with syntax highlighting: vim, gedit, emacs Marcin Młotkowski Object oriented programming 26 / 52

33 Editors with syntax highlighting: vim, gedit, emacs Tools idle PythonCard/codeEditor Marcin Młotkowski Object oriented programming 26 / 52

34 file.py Editors with syntax highlighting: vim, gedit, emacs Tools idle PythonCard/codeEditor "Executable"files and national characters: #!/usr/bin/python # -*- coding: iso *- Marcin Młotkowski Object oriented programming 26 / 52

35 Why "Python"? Marcin Młotkowski Object oriented programming 27 / 52

36 Further reading "Dive into Python", Mark Pilgrim... Marcin Młotkowski Object oriented programming 28 / 52

37 Outline On Python language 1 On Python language Marcin Młotkowski Object oriented programming 29 / 52

38 Simple types On Python language simple types: integers, floats, booleans sequential types: strings, lists, tuples Marcin Młotkowski Object oriented programming 30 / 52

39 Simple integers On Python language Range: [ sys.maxint 1, sys.maxint] Operators: +, -, /, //, %, ** Standard functions: abs(x), divmod(x, y) = (x // y, x % y) Warning Dividing integer by integer gives integer 4//3 = 1 Marcin Młotkowski Object oriented programming 31 / 52

40 Integers and conversions (1.0 4)//3 = 1.0 (1.0 4)/3 = float(4)/3 = 4/float(3) Marcin Młotkowski Object oriented programming 32 / 52

41 Large integers On Python language Example >>> 1000 ** L >>> long(100) 100L Marcin Młotkowski Object oriented programming 33 / 52

42 Constants On Python language Integers 0x123, 0x L, 0123, 06789L Floats e1 Marcin Młotkowski Object oriented programming 34 / 52

43 Complex numbers On Python language Literals and expressions 1 + 3j x + 12j complex(x, 0) Operators x.real 2 + y.imag 2 Marcin Młotkowski Object oriented programming 35 / 52

44 Standard numerical libraries math import math print math.cos(3.14) random from random import * print random() Marcin Młotkowski Object oriented programming 36 / 52

45 Examples On Python language Lists: [12,3] : "abc", def, u Zażółć żółtą jaźń tuples: (1, one, (1, 2+3j, 0x4)) dictionaries Sets Marcin Młotkowski Object oriented programming 37 / 52

46 Tuple On Python language brown = 165, 42, 42 NavyBlue = (0,0,128) htmlcolor = { turquoise : (64,224,208), NavyBlue : NavyBlue } r, g, b = htmlcol[ NavyBlue ] Marcin Młotkowski Object oriented programming 38 / 52

47 Reminder On Python language assignment a, b = 1, 2 Marcin Młotkowski Object oriented programming 39 / 52

48 Reminder On Python language assignment (a, b)= (1, 2) Marcin Młotkowski Object oriented programming 39 / 52

49 Inclusion operator On Python language in bc in abcd 4 not in [2, 3, 5, 7, 11] pi in { pi : , e : } Marcin Młotkowski Object oriented programming 40 / 52

50 Collection operators On Python language + >>> [ one, 2, 3.0 ] + [ 0x4, 05 ] [ one, 2, 3.0, 4, 5] >>> ( one, 2, 3.0) + (0x4, 05) ( one, 2, 3.0, 4, 5) Marcin Młotkowski Object oriented programming 41 / 52

51 Size of collection On Python language len len( [ one, 2, 3.0] ) len( { one : 1, two : 2 } ) len( (1, 2, 3) ) Marcin Młotkowski Object oriented programming 42 / 52

52 Elements of collections [1, 2, 3][2] = 3 Marcin Młotkowski Object oriented programming 43 / 52

53 Elements of collections [1, 2, 3][2] = 3 abcd [1:3] = bc Marcin Młotkowski Object oriented programming 43 / 52

54 Elements of collections [1, 2, 3][2] = 3 abcd [1:3] = bc (1, 2, 3)[1:] = (2, 3) Marcin Młotkowski Object oriented programming 43 / 52

55 Elements of collections [1, 2, 3][2] = 3 abcd [1:3] = bc (1, 2, 3)[1:] = (2, 3) (1,2,3)[:1] = (1, ) Marcin Młotkowski Object oriented programming 43 / 52

56 Elements of collections [1, 2, 3][2] = 3 abcd [1:3] = bc (1, 2, 3)[1:] = (2, 3) (1,2,3)[:1] = (1, ) Python [:-1] = Pytho Marcin Młotkowski Object oriented programming 43 / 52

57 Elements of collections [1, 2, 3][2] = 3 abcd [1:3] = bc (1, 2, 3)[1:] = (2, 3) (1,2,3)[:1] = (1, ) Python [:-1] = Pytho Python [-1:] = Python [-1] = n Marcin Młotkowski Object oriented programming 43 / 52

58 Slicing On Python language >>> informatics [::3] ioac Marcin Młotkowski Object oriented programming 44 / 52

59 Iterations over collections x = [1,2,3] y = [4,5,6] prod = 0 for i in range(len(x)): prod += x[i] * y[i] Marcin Młotkowski Object oriented programming 45 / 52

60 List processing On Python language x = [1,2,3] y = [4,5,6] prod = 0 for i, v in enumerate(x): prod += v * y[i] print prod Marcin Młotkowski Object oriented programming 46 / 52

61 List processing, other implementation x = [1,2,3] y = [4,5,6] prod = 0 for a, b in zip(x, y): prod += a * b print prod Marcin Młotkowski Object oriented programming 47 / 52

62 Dictionary processing iteration dict = { uno : 1, duo : 2, tre : 3 } for key, val in dict.iteritems(): print key, "=", val Marcin Młotkowski Object oriented programming 48 / 52

63 Constants On Python language Alice has a cat Alice has a cat Marcin Młotkowski Object oriented programming 49 / 52

64 Constants On Python language Alice has a cat Alice has a cat Unicode uźażółć żółtą jaźń" "Zażółć żółtą jaźń" Marcin Młotkowski Object oriented programming 49 / 52

65 Constants On Python language Alice has a cat Alice has a cat Unicode uźażółć żółtą jaźń" "Zażółć żółtą jaźń" Unicode len(u"żółty") == 5 len("żółty") == 8 Marcin Młotkowski Object oriented programming 49 / 52

66 Constants On Python language Alice has a cat Alice has a cat Unicode uźażółć żółtą jaźń" "Zażółć żółtą jaźń" Unicode len(u"żółty") == 5 len("żółty") == 8 Long strings """This is a multiline string"""" Marcin Młotkowski Object oriented programming 49 / 52

67 On Python language are collections raw strings: r abcd\n String continuation: "This is a \n\ very long string\n" A lot of library functions are immutable, ie. abc [1] = d Marcin Młotkowski Object oriented programming 50 / 52

68 String formatting On Python language Operator % print "%i + %i = %i\n" % (2, 2, 2+2) dict = { two : 2, four : 4 } print "%(two)s + %(two)s = %(four)s\n" % dict Marcin Młotkowski Object oriented programming 51 / 52

69 First aid On Python language Interactive mode >>> type(3.1415) <type float > >>> dir(float)... >>> dir(3.1415)... >>> float. doc Marcin Młotkowski Object oriented programming 52 / 52

Senthil Kumaran S

Senthil Kumaran S http://www.stylesen.org/ Agenda History Basics Control Flow Functions Modules History What is Python? Python is a general purpose, object-oriented, high level, interpreted language Created