Python Tutorial

1. Python Tutorial Learning Python 5th Edition

2. Why Python • Python is a general-purpose programming language that is often applied in scripting roles. It is commonly defined as an object-oriented scripting language • Why we use python • Software quality • Developer productivity • Program portability • Support libraries • Component integration • Enjoyment

3. Who Uses Python Today? • Google, YouTube ,Dropbox storage service, The Raspberry Pisingle-board computer, • EVE Online, a massively multiplayer online game (MMOG) by CCP Games, • The widespread Bit Torrent peer-to-peer file sharing system, • Industrial Light & Magic, Pixar, and others use Python in the production of animated movies. • ESRI uses as customization tool for its popular GIS mapping products. • Google’s App Engine web development framework • The Iron Port email server product • Maya, a powerful integrated 3D modeling and animation system, • The NSA uses Python for cryptography and intelligence analysis. • iRobot uses Python to develop commercial and military robotic devices

4. What can I do with python • Systems Programming • GUIs • Internet Scripting • Component Integration • Database Programming • Rapid Prototyping • Numeric and Scientific Programming • And More: Gaming, Images, Data Mining, Robots, Excel...

5. How Python Runs Programs? • Python Interpreter • An interactive version of python that works in interpreted way • Hello to interpreter • Make a file with name script0.py • Write this code and save it • Run Program as

6. How you run programs • Interactive way • Starting the python • Or use GUI based environment • Entering multiline statements

7. First Script • Make a file in text editor (i.e. notepad) with name script1.py • Run it like below • route the printed output of a Python script to a file to save it for later use

8. Module import and reloads • every file of Python source code whose name ends in a .py extension is a module • You can import the file within python environment as • To use script again and again in running session • Use reload method • A module is mostly just a package of • variable names (known as a Namespace) • the names within that package are called attributes. • An attribute is simply a variable name that is attached to a specific object (like a module)

9. Module Properties • Make a variable in a file called myfile.py • Make a file threenames.py title = "The Meaning of Life"

10. Modules and namespaces • modules • are the largest program structure in Python programs, and one of the first key concepts in the language • Name Space • Python programs are composed of multiple module files linked together by import statements, and each module file is a package of variables • each module is a self-contained namespace • there are more ways to run code stored in module files

11. Variable Name Rules • Syntax: (underscore or letter) + (any number of letters, digits, or underscores) • Case matters: SPAM is not the same as spam • Reserved words are off-limits • Naming conventions • Names that begin with a single underscore (_X) are not imported by a from module import * statement • Names that have two leading and trailing underscores (__X__) are system-defined names that have special meaning to the interpreter • Names that begin with two underscores and do not end with two more (__X) are localized (“mangled”) to enclosing classes • The name that is just a single underscore (_) retains the result of the last expression when you are working interactively

12. Types and Operations • The Python Conceptual Hierarchy • Programs are composed of modules. • Modules contain statements. • Statements contain expressions. • Expressions create and process objects.

13. Classes

14. Python Expressions

15. Variables and Basic Expressions • Variables are created when they are first assigned values. • Variables are replaced with their values when used in expressions. • Variables must be assigned before they can be used in expressions. • Variables refer to objects and are never declared ahead of time. • comment

16. Dynamic Typing • Variables, Objects, and References

17. Reference Checking

18. String • Python strings are categorized as immutable sequences

19. String • Implicit concatenation: title = "Meaning " 'of' " Life“ • Concatenation: • Repetition: • Triple Quotes Code Multiline Block Strings

20. String Indexing and Slicing • X[1:10:2] • will fetch every other item in X from offsets 1–9 • Character code conversions

21. Changing Strings • Strings are immutable • Method Call Syntax • Attribute fetches • An expression of the form object.attribute means “fetch the value of attribute in object. • Call expressions • An expression of the form function(arguments) means “invoke the code of function, passing zero or more comma-separated argument objects to it, and return function’s result value • Method call expression: • object.method(arguments)

22. String class methods

23. String Methods: Examples

24. String Method Examples: Parsing Text

25. Other Common String Methods in Action

26. String Formatting Expressions • Allows us to perform multiple type-specific substitutions on a string in a single step • String formatting expressions: '...%s...' % (values) • String formatting method calls: '...{ }...'.format(values) • Dictionary-Based Formatting Expressions

27. String Formatting Method Calls

28. Lists and Dictionaries • Lists • Ordered collections of arbitrary objects • Accessed by offset • Variable-length, heterogeneous, and arbitrarily nestable • Of the category “mutable sequence” • Arrays of object references

29. Lists

30. Dictionaries • Accessed by key, not offset position • Unordered collections of arbitrary objects • Variable-length, heterogeneous, and arbitrarily nestable • Of the category “mutable mapping” • Tables of object references (hash tables)

32. Tuples, Files, and Everything Else • Tuples • Ordered collections of arbitrary objects • Accessed by offset • Of the category “immutable sequence” • Fixed-length, heterogeneous, and arbitrarily nestable • Arrays of object references

33. Tuples in Action • Concatenation • Repetition • Indexing/Slicing

34. Files

35. Files in Action

36. Storing Python Objects in Files: Conversions

37. Statements and Syntax

38. Assignment Statements

39. Expression Statements

40. Decision Statements

41. Switch statement Block Delimiters: Indentation Rules Statement Delimiters: Lines and Continuations Statements may span multiple lines if you’re continuing an open syntactic pair Statements may span multiple lines if they end in a backslash

42. Loops

43. Handling Errors with try Statements

44. Functions and Generators • def is executable code • def creates an object and assigns it to a name • lambda creates an object but returns it as a result • return sends a result object back to the caller • yield sends a result object back to the caller, but remembers where it left off • global declares module-level variables that are to be assigned • nonlocal declares enclosing function variables that are to be assigned • Arguments are passed by assignment (object reference) • Arguments are passed by position, unless you say otherwise • Arguments, return values, and variables are not declared def Executes at Runtime

45. Functions: Examples Definition Arbitrary scope nesting Calls

46. Arguments • Arguments are passed by automatically assigning objects to local variable names • Assigning to argument names inside a function does not affect the caller • Changing a mutable object argument in a function may impact the caller • Immutable arguments are effectively passed “by value.” • Mutable arguments are effectively passed “by pointer.”

47. Keyword and Default Examples

48. Arbitrary Arguments Examples • The last two matching extensions, * and ** (for keyword arguments only) , are designed to support functions that take any number of arguments.