Intro to Ruby Scripting

Transcription

1 Intro to Ruby Scripting Dimitrios Galanakis Thursday April 15th A Tutorial for the LSU Center for Computation and Technology

2 Why Scripting? Advantages Flexible, portable, reusable, short code No need for compilation Access to diverse libraries Glue among different tools Minimum programming knowledge required Disadvantages Relatively slow, but the gap has closed

3 Why Ruby? Pure object oriented language Compact, clean syntax, short code Powerful integration with Regular Expressions Blocks Meta programming Large set of libraries Web developers: Ruby on Rails

4 Getting Started Versions: Ruby 1.8: old but still used Ruby 1.9: the future and largely debugged Installation: Mac: version 1.8 comes preinstalled. Latest version from Macports Linux: All distributions have it preinstalled or provide a package. Windows: One-click installer. Run: ruby <source_filename>: executes the source./source_filename: if it is executable and prefixed by #!/path/to/bin/ruby Interactive RuBy: irb On the browser (zero install):

5 Object Oriented Programming class Person def def greet puts "Hello, def def def def Class: a collection of data and methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

6 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

7 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

8 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

9 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

10 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

11 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

12 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method accessor methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

13 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method accessor methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

14 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method accessor methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

15 Object Oriented Programming Class: a collection of data and methods class Person def "+@phone def greet puts "Hello, "+@name def def def def class names should be capitalized Initializer instance variables name, phone: local variables a method another method accessor methods set methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s

16 Object Oriented Programming class Person def def greet puts "Hello, def def def def Class: a collection of data and methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s class names should be capitalized Initializer instance variables name, phone: local variables a method another method accessor methods set methods Output

17 Object Oriented Programming class Person def def greet puts "Hello, def def def def Class: a collection of data and methods me=person.new("dimitris Galanakis"," ") me.greet puts me.phone another_me=me another_me.phone= another_me.to_s class names should be capitalized Initializer instance variables name, phone: local variables a method another method accessor methods set methods Output Hello, Dimitris Galanakis Dimitris Galanakis:

18 Class Inheritance A class can be defined as a child of another class. This results in inheriting all the methods and and data in addition to the new ones. Single inheritance: a class has only one parent (like Java and unlike C++). Multiple inheritance is simulated through Modules class Person attr :phone, :name def "+@phone class Employee < Person attr :department def initialize(name,phone,department) def to_s super.to_s+" at the "+@department+" department." alice=employee.new("alice","234234","physics") puts alice.to_s

19 Class Inheritance A class can be defined as a child of another class. This results in inheriting all the methods and and data in addition to the new ones. Single inheritance: a class has only one parent (like Java and unlike C++). Multiple inheritance is simulated through Modules class Person attr :phone, :name def "+@phone auto generate the accessor and setter methods class Employee < Person attr :department def initialize(name,phone,department) def to_s super.to_s+" at the "+@department+" department." alice=employee.new("alice","234234","physics") puts alice.to_s

20 Class Inheritance A class can be defined as a child of another class. This results in inheriting all the methods and and data in addition to the new ones. Single inheritance: a class has only one parent (like Java and unlike C++). Multiple inheritance is simulated through Modules class Person attr :phone, :name def "+@phone auto generate the accessor and setter methods Person objects instance variables class Employee < Person attr :department def initialize(name,phone,department) def to_s super.to_s+" at the "+@department+" department." alice=employee.new("alice","234234","physics") puts alice.to_s

21 Class Inheritance A class can be defined as a child of another class. This results in inheriting all the methods and and data in addition to the new ones. Single inheritance: a class has only one parent (like Java and unlike C++). Multiple inheritance is simulated through Modules class Person attr :phone, :name def "+@phone auto generate the accessor and setter methods Person objects instance variables Employee will be a more specific Person class Employee < Person attr :department def initialize(name,phone,department) def to_s super.to_s+" at the "+@department+" department." alice=employee.new("alice","234234","physics") puts alice.to_s

22 Class Inheritance A class can be defined as a child of another class. This results in inheriting all the methods and and data in addition to the new ones. Single inheritance: a class has only one parent (like Java and unlike C++). Multiple inheritance is simulated through Modules class Person attr :phone, :name def "+@phone auto generate the accessor and setter methods Person objects instance variables Employee will be a more specific Person class Employee < Person attr :department def initialize(name,phone,department) def to_s super.to_s+" at the "+@department+" department." Calls the parent classes initializer alice=employee.new("alice","234234","physics") puts alice.to_s

23 Class Inheritance A class can be defined as a child of another class. This results in inheriting all the methods and and data in addition to the new ones. Single inheritance: a class has only one parent (like Java and unlike C++). Multiple inheritance is simulated through Modules class Person attr :phone, :name def "+@phone class Employee < Person attr :department def initialize(name,phone,department) auto generate the accessor and setter methods Person objects instance variables Employee will be a more specific Person def to_s super.to_s+" at the "+@department+" department." alice=employee.new("alice","234234","physics") puts alice.to_s Calls the parent classes initializer Employee @department instance variables

24 Modules Implement functions that can be shared between classes Multiple inheritance is simulated through Modules module VerboseToS def verbose_tos implement a method that relies on the to_s "This is a rather verbose way to say that "+to_s class Employee include VerboseToS classes can open and close any time include all the methods from VerboseToS module puts alice.verbose_tos Output: This is a rather verbose way to say that alice: at the Physics department.

25 Object Oriented Programming Overview A class is a definition of data + methods An object is an instance of the class and is born by calling the class initializer. The methods of an object are called to access or modify it s data. A class can inherit the data and methods of another class. Modules are collections of methods than can be inserted to any class. Each class inherits only from a single class, but can include many modules. All classes are implicit children of the built in class Object.

26 Basic Ruby Classes Numeric: Integers, Rationals, Floats, Complex Strings: Any alphanumeric between or Regular Expressions: /\w+/ Indexed Collections: Arrays and Hashes

27 Numbers Integers, Rationals, Floats, Complex Source a=13 b=100 puts a*b puts a+b puts 1.2*b-a puts a**b puts a.quo(b) a=math.sin(2.4345)+10 puts a require 'complex' include Math z=complex(4,5) puts atan(z) puts z.arg puts z.real.to_s+","+z.imag.to_s Output / i ,5

28 Strings String: a series of alphanumeric characters in or, such as Hello, World In the strings all characters are literal, but the strings can represent special characters, such as \n, \t etc. prefix='datafile' suffix=".dat" label=200.to_s filename=prefix+label+suffix string="reading #{filename}\n\n" command_string=%x{ls -l #{filename}} string_array=%w{this will create an array of those words}

29 Strings String: a series of alphanumeric characters in or, such as Hello, World In the strings all characters are literal, but the strings can represent special characters, such as \n, \t etc. prefix='datafile' suffix=".dat" label=200.to_s filename=prefix+label+suffix string="reading #{filename}\n\n" command_string=%x{ls -l #{filename}} string concatenate => datafile200.dat string_array=%w{this will create an array of those words}

30 Strings String: a series of alphanumeric characters in or, such as Hello, World In the strings all characters are literal, but the strings can represent special characters, such as \n, \t etc. prefix='datafile' suffix=".dat" label=200.to_s filename=prefix+label+suffix string="reading #{filename}\n\n" command_string=%x{ls -l #{filename}} string concatenate => datafile200.dat Reading datafile200.dat string_array=%w{this will create an array of those words}

31 Strings String: a series of alphanumeric characters in or, such as Hello, World In the strings all characters are literal, but the strings can represent special characters, such as \n, \t etc. prefix='datafile' suffix=".dat" label=200.to_s filename=prefix+label+suffix string="reading #{filename}\n\n" command_string=%x{ls -l #{filename}} string concatenate => datafile200.dat Reading datafile200.dat returns the output of a system command string_array=%w{this will create an array of those words}

32 Regular Expressions Defines a text pattern Can be used for pattern matching and extraction Exactly the same as in perl, awk, sed, egrep, python, etc. Essential for text manipulation, replacement, data extraction \w (\W) any alphanumeric character (opposite) \d (\D) any digit (opposite). any character \. the dot character [ ] ranges and sets of characters ( ) a group (you can refer to it later) + once or more * zero or more times

33 Regular Expressions Defines a text pattern Can be used for pattern matching and extraction Exactly the same as in perl, awk, sed, egrep, python, etc. Essential for text manipulation, replacement, data extraction \w (\W) any alphanumeric character (opposite) \d (\D) any digit (opposite). any character \. the dot character [ ] ranges and sets of characters ( ) a group (you can refer to it later) + once or more * zero or more times line="filling= / " floatpattern=/=(\d+\.*\d*)/ filling=line[floatpattern,1].to_f

34 Regular Expressions Defines a text pattern Can be used for pattern matching and extraction Exactly the same as in perl, awk, sed, egrep, python, etc. Essential for text manipulation, replacement, data extraction \w (\W) any alphanumeric character (opposite) \d (\D) any digit (opposite). any character \. the dot character [ ] ranges and sets of characters ( ) a group (you can refer to it later) + once or more * zero or more times line="filling= / " floatpattern=/=(\d+\.*\d*)/ filling=line[floatpattern,1].to_f =

35 Arrays and Hashes Dynamic, Indexed collections of objects Arrays: the index is an integer (zero based) Hashes: a map or dictionary from any object (called the key) to another object called value. [ ] : Initialize arrays of objects { } : Initialize hashes of objects

36 Array/Hash Examples a=[3,"english",32,"german","greek",:test] puts a[1]+" and "+a[4] puts a.values_at(0,3,4)*"," English and Greek 3,German,Greek h={ 'cello'=>'string', 'clarinet'=>'woodwind', 'drum' => 'percussion', 'trumpet' => 'woodwind', 'violin' => 'string' } puts h['cello'] puts h['clarinet'] string woodwind

37 Symbols Symbol: a constant integer. Same as the enum in C. It is prefixed by : (Example :symbol) Excellent choice for a hash key. hello.to_sym instrument_types={:cello => 'string', :drum => 'percussion'} instrument_types={cello:'string', drum:'percussion'}

38 Symbols Symbol: a constant integer. Same as the enum in C. It is prefixed by : (Example :symbol) Excellent choice for a hash key. hello.to_sym convert a string to a symbol instrument_types={:cello => 'string', :drum => 'percussion'} instrument_types={cello:'string', drum:'percussion'}

39 Symbols Symbol: a constant integer. Same as the enum in C. It is prefixed by : (Example :symbol) Excellent choice for a hash key. hello.to_sym instrument_types={:cello => 'string', :drum => 'percussion'} instrument_types={cello:'string', drum:'percussion'} convert a string to a symbol symbols make ideal hash keys

40 Symbols Symbol: a constant integer. Same as the enum in C. It is prefixed by : (Example :symbol) Excellent choice for a hash key. hello.to_sym instrument_types={:cello => 'string', :drum => 'percussion'} instrument_types={cello:'string', drum:'percussion'} convert a string to a symbol symbols make ideal hash keys Identical to the previous (Ruby 1.9)

41 Control Structures There aren t many that are practically used. Mainly if and while. happy=true if(happy) puts "Hello World" else puts "Goodbye World" puts (happy)? "Hello World" : "Goodbye World" puts "I am happy" if happy C/C++ syntax compact if while(line=gets) puts line

42 Blocks A block is an anonymous function passed as an argument One of Ruby s most pressious feature! Allows for compact and general code Natural way to iterate over collections def fib_up_to(max) i1, i2 = 1, 1 while i1 <= max yield i1 i1, i2 = i2, i1+i2 parallel assignment yield will call the block with f=i1 fib_up_to(1000) { f print f, " " } Output:

43 Typical Containers and Iterators Array.each: execute the block with the element as the argument: a=[1,2,3,4,5] a.each{ e puts e} Array.each_with_index: same but the index is also passed as an argument: a.each_with_index{ e,i puts "index= "+i.to_s+" value= "+e.to_s} Array.collect: replace every element with the result of the block: squares=a.collect{ e e*e} Hash.each: execute the block with the key/value as the arguments h={cello:"string",drum:"percussion"} h.each{ k,v puts k.to_s+" is a "+v+" instrument"} File.open: open a file and pass it s handler to the block: File.open(data.txt) { f while(line=f.gets) puts line }

44 Introduction to Metaprogramming Programmatically generate and insert new code. attr is an example of metaprogramming: it generates and inserts the accessor and setter functions. code = <<-";" def hello puts "Hello" ; puts code instance_eval(code) hello code= def hello puts Hello the code is inserted in the script the defined function can be called.

45 Real Life Application A simple command line tool that will read text, extracts parameters and executes commands on them.

46 Step 1: Input file format Let s assume something about the input Major program output beta iso filling mu = 3.5 Energy per site is: We will extract mu, beta and energy

47 Step 1: Input file format Let s assume something about the input Major program output beta iso filling line.split[0] mu = 3.5 Energy per site is: We will extract mu, beta and energy

48 Step 1: Input file format Let s assume something about the input Major program output beta iso filling mu = 3.5 line.split[0] /mu\ *=\ *(\d+\.*\d*)/ Energy per site is: We will extract mu, beta and energy

49 Step 1: Input file format Let s assume something about the input Major program output beta iso filling mu = 3.5 Energy per site is: line.split[0] /mu\ *=\ *(\d+\.*\d*)/ /Energy[\ \w:]+(\d+\.*\d*)/ We will extract mu, beta and energy

50 Step 2: Implement the data file parser The parser will be implemented as a module so that it can be inserted in any class that may need to know how to read it. module DataFile def read(filename) mupattern=/mu\ *=\ *(\d+\.*\d*)/ energypattern=/energy[\ \w:]+(\d+\.*\d*)/ File.open(filename) { f reg. ex. for mu and energy open the file for reading read it line by line if if line[energypattern,1] }

51 Step 2.5: Including the data file parser class Parameters include DataFile attr :mu, :beta, :energy def initialize(filename) read(filename) def to_s the initialization consists of reading the file into the parameters "Beta= "+beta.to_s+" mu= "+mu.to_s+" energy= "+energy.to_s data.txt Major program output beta iso filling mu = 3.5 Calling code p=parameters.new("data.txt") puts p.to_s Print output Beta= 10.0 mu= 3.5 energy= Energy per site is: 0.254

52 Step 3: Parse command line arguments All the arguments are stored in an array called ARGV We will assume that the first argument is the command and the rest are the files. The command will have arbitrary syntax. tool.rb <command> <files>

53 Step 3.5: Implement a basic parser if(argv.size<2 or!file.exist?(argv[1])) puts "Usage: tool.rb <command> files" exit command="def exec\n"+argv.shift+"\n" Insert command in the class definition. Parameters.module_eval(command) Minimal input validation shift: return the first element after removing it. command= def exec <command> Replace the filenames by the data structures parameters=argv.collect { f Parameters.new(f)} Execute the command for each parameter set. parameters.each { p p.exec} Example: ruby tool.rb puts mu**2 data* Will read all files and print the mu squared

54 Further reading I am not paid by this guy. I find this book a really good introduction and reference. The version for Ruby 1.6 is free online.