1. Installation, Data types, Control flow structures, Loops, Functions, Strings, OOP, Data Structures, Tuples, Destructuring Assignments Telerik Academy Plus http://academy.telerik.com Python Overview

2.  Python Overview  Installing Python  Python IDEs  Data types  Control flow structures  Loops  Data Structures and comprehensions  Lists, sets, dictionaries and tuples  Destructuring assignments

3.  Functions  Lambda functions  Modules  Object-oriented programming  Creating classes  Properties, instance and class methods  Inheritance  Best Practices  The Zen of Python

4. What is Python? What can be used for?

5.  Python is a widely used general-purpose, high- level programming language  Its design philosophy emphasizes code readability  Its syntax allows programmers to express concepts in fewer lines of code  The language provides constructs intended to enable clear programs on both a small and large scale

6.  Python supports multiple programming paradigms, including  Object-oriented  Imperative and functional programming  It features a dynamic type system and automatic memory management  Python is widely used for:  Web applications development: Django, Pyramid  Games with PyGame  Automations scripts, Sikuli  And more

7. On MAC, Linux and Windows

8.  On MAC  Homebrew can be used $ brew install python  On Linux  Part of Linux is built with Python, so it comes out- of-the-box  On Windows  Download the installer from https://www.python.org/ https://www.python.org/  Add the installation path to System Variables $PATH

9. Live Demo

10.  Open the CMD/Terminal and run:  You can run python code:  Print the numbers from 0 to 4 $ python for i in range(5): print(i) print(i) sum = 0 for i in range(5, 10): sum += i sum += iprint(sum)  Sum the numbers from 5 to 9

11.  Open the CMD/Terminal and run:  You can run python code:  Print the numbers from 0 to 4 $ python for i in range(5): print(i) print(i) sum = 0 for i in range(5, 10): sum += i sum += iprint(sum)  Sum the numbers from 5 to 9 Significant whitespace matters a lot

12.  Significant whitespace is a way to write code in python  This is actually the indentation  Significant whitespace creates blocks in python code  It is the equivalent of curly brackets ( {} ) in other languages  Good practices say "Use four spaces for indent"

13. Sublime Text, PyCharm, REPL

14.  Python is quite popular and there are my IDEs:  PyCharm  Commercial and Community editions  Ready-to-use  Sublime Text  Free, open-source  Needs plugins and some setup to work proper ly  LiClipse  Free, based on Eclipse  Ready-to-use

15. Live Demo

16. int, float, etc

17.  Python supports all the primary data types:  int – integer numbers  int(intAsString) parses a string to int  float – floating-point numbers  float(floatAsString) parses a string to float  None – like null  bool – Boolean values (True and False)  str – string values (sequence of characters)

18. Live Demo

19. If-elif-else

20.  Python supports conditionals: if conditionOne: # run code if conditionOne is True # run code if conditionOne is True elif conditionTwo: # run code if conditionOne is False # run code if conditionOne is False # but conditionTwo is True # but conditionTwo is True else # run code if conditionOne and # conditionTwo are False  The conditions are True-like and False-like  ""(empty string), 0, None are evaluated to False  Non-empty strings, any number or object are evaluated to True

21. Live Demo

22. for and while

23.  There are two types of loops in Python  for loop for i in range(5): # run code with values of i: 0, 1, 2, 3 and 4 # run code with values of i: 0, 1, 2, 3 and 4 names = ['Doncho', 'Asya', 'Evlogi', 'Nikolay', 'Ivaylo'] for i in range(len(names)): print('Hi! I am %s!'%names[i]); print('Hi! I am %s!'%names[i]);  while loop number = 1024 binNumber = ''; while number >= 1: binNumber += '%i'%(number%2) binNumber += '%i'%(number%2) number /= 2 number /= 2print(binNumber[::-1])

24. Live Demo

25. Lists, Dictionaries, Sets

26.  Python has three primary data structures  List  Keep a collection of objects  Objects can be accessed and changed by index  Objects can be appended/removed dynamically  Dictionary  Keep a collection of key-value pairs  Values are accessed by key  The key can be of any type  Sets  Keep a collection of unique objects

27. Collections of objects

28.  Lists are created using square brackets ( '[' and ']' ): numbers = [1, 2, 3, 4, 5, 6, 7] names = ["Doncho", "Niki", "Ivo", "Evlogi"]  Print a list of items:  Object by object for name in names: print(name) print(name)  Add new object to the list: names.append("Asya")  Or by index: for index in len(names): print(names[index]) print(names[index])

29. Live Demo

30.  List comprehensions are a easier way to create lists with values  They use the square brackets ( '[' and ']' ) and an expression inside even = [number for number in numbers if not number % 2] longerNames = [name for name in names if len(name) > 6] kNames = [name for name in names if name.startswith("K")] [eat(food) for food in foods if food is not "banana"]

31. Live Demo

32. Collections of unique values

33.  Sets are created like lists, but using curly brackets instead of square  They contain unique values  i.e. each value can be contained only once  __eq__(other) methods is called for each object names = {"Doncho", "Nikolay"} names.add("Ivaylo")names.add("Evlogi")names.add("Doncho")print(names) # the result is {'Nikolay', 'Ivaylo', 'Evlogi', 'Doncho'} # 'Doncho' is contained only once

34. Live Demo

35.  Set comprehensions are exactly like list comprehensions  But contain only unique values sentence = "Hello! My name is Doncho Minkov and …" parts = re.split("[,!. ]", sentence) words = {word.lower() for word in parts if word is not ""}

36. Live Demo

37. Key-value pairs

38.  Dictionary is a collection of key-value pairs  The key can be of any type  For custom types, the methods __hash__() and __eq__(other) must be overloaded  Values can be of any type  Even other dictionaries or lists musicPreferences = { "Rock": ["Peter", "Georgi"], "Rock": ["Peter", "Georgi"], "Pop Folk": ["Maria", "Teodor"], "Pop Folk": ["Maria", "Teodor"], "Blues and Jazz": ["Alex", "Todor"], "Blues and Jazz": ["Alex", "Todor"], "Pop": ["Nikolay", "Ivan", "Elena"] "Pop": ["Nikolay", "Ivan", "Elena"]}

39. Live Demo

40.  Dictionary comprehensions follow pretty much the same structure as list comprehensions  Just use curly brackets {} instead of square []  Provide the pair in the format key: value names = {trainer.name for trainer in trainers} trainersSkills = { name: [] for name in names} {trainersSkills[trainer.name].append(trainer.skill) for trainer in trainers} for trainer in trainers}

41. Live Demo

43.  A tuple is a sequence of immutable objects  Much like lists, but their values cannot be changed  Use parenthesis instead of square brackets languages = ("Python", "JavaScript", "Swift") for lang in languages: print(lang) print(lang) print("Number of languages: {0}".format(len(languages))

44. Live Demo

45.  The following operations are supported for tuples:  Get the length of the tuple: len((-1, 5, 11)) # returns 3 (1, 2) + (7, 8, 9) # returns (1, 2, 7, 8, 9)  Concatenate tuples: (1,)*5 # returns (1, 1, 1, 1, 1)  Multiply by number:  Check for value: 3 in (1, 2, 3) # returns True

46. Live Demo

48.  Destructuring assignments (bind) allow easier extracting of values  With tuples  With arrays x, y = 1, 5 # equivalent to x = 1 and y = 5 x, y = y, x # swap the values numbers = [1, 2] [one, two] = numbers numbers = list(range(1, 10)) [first, *middle, last] = numbers

49. Live Demo

50. Separate the code in smaller and reusable pieces

51.  Functions in Python:  Are defined using the keyword "def"  Have an identifier  A list of parameters  A return type def toBin(number): bin = '' bin = '' while number >= 1: while number >= 1: bin += '%i'%(number%2) bin += '%i'%(number%2) number /= 2 number /= 2 return bin[::-1] return bin[::-1]

52. Live Demo

53.  Python allows the creation of anonymous functions (lambda functions)  Using the keyword lambda and a special syntax: printMsg = lambda msg: print('Message: {0}'.format(msg))  Same as: def printMsg2(msg): print('Message: {0}'.format(msg)) print('Message: {0}'.format(msg))  Mostly used for data structures manipulation evenNumbers = filter(lambda n: not n%2, numbers)

54. Live Demo

55. How to separate the code in different modules

56.  Python applications are separated into modules  These module represent just a list of functions and/or classes  To use all functions from a module numeralSystems : import numeralSystems print(numeralSystems.toBin(1023))print(numeralSystems.toHex(1023)) from numeralSystems import toBin as bin  A single function:  Or some functions from numeralSystems import toBin as bin, toHex as hex

57. Live Demo

58. With Python

59.  Python is an object-oriented language  Support for classes, inheritance, method overloading, etc…  To create a class:  Use the keyword class  Give the class a name  Define __init__ method and other methods  Attributes (fields) are defined inside the contructor ( __init__ ) method class Presentation: def __init__(self, title, duration): def __init__(self, title, duration): self.title = title self.title = title self.duration = duration self.duration = duration

60. Live Demo

61.  Python has a concept for providing properties for class attributes  Properties are used for data hiding and validation of the input values class Presentation: def __init__(self, title, duration): def __init__(self, title, duration): self.title = title self.title = title self.duration = duration self.duration = duration @property @property def duration(self): def duration(self): return self._duration return self._duration @duration.setter @duration.setter def duration(self, value): def duration(self, value): if(0 < duration and duration <= 4): if(0 < duration and duration <= 4): self._duration = value self._duration = value

62. Live Demo

63.  Instance methods are methods that are used on a concrete instance of the class  To create an instance method, provide self as first parameter to the method: class Trainer(Person): # … # … def deliver(self, presentation): def deliver(self, presentation): print("{0} is delivering presentation about {1}" print("{0} is delivering presentation about {1}".format(self.name, presentation.title)).format(self.name, presentation.title))

64.  Instance methods are methods that are used on a concrete instance of the class  To create an instance method, provide self as first parameter to the method: class Trainer(Person): # … # … def deliver(self, presentation): def deliver(self, presentation): print("{0} is delivering presentation about {1}" print("{0} is delivering presentation about {1}".format(self.name, presentation.title)).format(self.name, presentation.title)) self is like this for other languages

65. Live Demo

66.  Class methods are shared between all instances of the class, and other objects  They are used on the class, instead of on concrete object  Defined as regular functions  But inside the class  Without self as parameter class Person: # … # … def validate_person_age(age): def validate_person_age(age): return 0 < age and age < 150 return 0 < age and age < 150

67. Live Demo

68. Extend classes

69.  Class inheritance is the process of creating a class that extends the state and behavior of other class  Functions and attributes are inherited  New functions and attributes can be added class Person: def __init__(self, name, age): def __init__(self, name, age): self.name = name self.name = name self.age = age self.age = age class Trainer(Person): def __init__(self, name, age, speciality): def __init__(self, name, age, speciality): super().__init__(name, age) super().__init__(name, age) self.speciality = speciality self.speciality = speciality def deliver(self, presentation): def deliver(self, presentation): print("{0} is delivering presentation about {1}" print("{0} is delivering presentation about {1}".format(self.name, presentation.title)).format(self.name, presentation.title))

70.  Class inheritance is the process of creating a class that extends the state and behavior of other class  Functions and attributes are inherited  New functions and attributes can be added class Person: def __init__(self, name, age): def __init__(self, name, age): self.name = name self.name = name self.age = age self.age = age class Trainer(Person): def __init__(self, name, age, speciality): def __init__(self, name, age, speciality): super().__init__(name, age) super().__init__(name, age) self.speciality = speciality self.speciality = speciality def deliver(self, presentation): def deliver(self, presentation): print("{0} is delivering presentation about {1}" print("{0} is delivering presentation about {1}".format(self.name, presentation.title)).format(self.name, presentation.title)) Trainer inherits Person

71.  Class inheritance is the process of creating a class that extends the state and behavior of other class  Functions and attributes are inherited  New functions and attributes can be added class Person: def __init__(self, name, age): def __init__(self, name, age): self.name = name self.name = name self.age = age self.age = age class Trainer(Person): def __init__(self, name, age, speciality): def __init__(self, name, age, speciality): super().__init__(name, age) super().__init__(name, age) self.speciality = speciality self.speciality = speciality def deliver(self, presentation): def deliver(self, presentation): print("{0} is delivering presentation about {1}" print("{0} is delivering presentation about {1}".format(self.name, presentation.title)).format(self.name, presentation.title)) super() calls the parent

72. Live Demo

73. How to write readable Python code?

74.  Use 4-space indentation, and no tabs  Wrap lines so that they don’t exceed 79 characters  Use blank lines to separate functions and classes  Use docstrings  Use spaces around operators and after commas  Name your classes and functions consistently  PascalCase for classes  lower_case_with_underscores for functions and methods

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