python 与 ruby 之间的区别

[color=red][b]Number 类型[/b][/color]

python 是 int 和 long
ruby 是 Fixnum 和 Bignum

num = 8
7.times do
  print num.type, " ", num, "\n"
  num *= num
end

produces: Fixnum 8
Fixnum 64
Fixnum 4096
Fixnum 16777216
Bignum 281474976710656
Bignum 79228162514264337593543950336
Bignum 6277101735386680763835789423207666416102355444464034512896

[color=red][b]对象区别[/b][/color]

isinstance(object, classinfo) #是否为类或继承类的实例

class A(object):
...     pass
... class B(A):
...     pass
>>> b = B()
>>> isinstance(b,B)
59: True
>>> isinstance(b,A)
60: True

instance_of?(object, classinfo) #是否为该类
kind_of?(object, classinfo) # #是否为类或继承类的实例

[color=red][b]String 类型[/b][/color]

1. 类型

>>> type("s")
20: 
>>> type(u"s")
21: 

irb(main):236:0> "dd".type
=> String

2.字符串格式化

>>> print '%s %s' % ("hi"，"world")
>>> print '%(name)s %(v)s' % {"name":1 ,"v":2}

>>> a= "world"
>>> puts "hello \t #{a}"

3. print函数

>>> print "hi world" #换行
>>>  print "hi world", #不换行

>>> puts "hi world" #换行
>>>  print "hi world"  #不换行

4.多行字符串

astring = """
   The body of the string
    is the input lines up to
    one ending with the same
    text that followed the '<<'
"""

aString = <    The body of the string
    is the input lines up to
    one ending with the same
    text that followed the '<<'
END_OF_STRING

字符串拼接，这个比较重要要提一下join方法

 ",".join([1,2,3])

[1,2,3].join(",")

5.ruby的其他表现形式

>>> %q {hi world} #single-quoted string 
>>>  %Q {hi world} #double-quoted string 

[color=red][b]Range 类型[/b][/color]

在这里ruby 使用 a.to_enum （Included Modules Enumerable）的方法对序列进行迭代，而python的range 直接生成一个数组，python的xrange的实现与 ruby的Enumerable类似

>>> range(10)
>>> xrange(10)

>>> (0..9).to_a 
>>> 0..9

[color=red][b]Regular Expressions[/b][/color]
ruby 里的正则表达式似乎没有global 参数
IGNORECASE: INT2FIX(RE_OPTION_IGNORECASE)
EXTENDED: INT2FIX(RE_OPTION_EXTENDED)
MULTILINE: INT2FIX(RE_OPTION_MULTILINE)

>>> a = "Fats Waller"  
>>> a =~ /a/  #这里返回匹配位置

python 也没有global 但是有 DOTALL 并且支持re.UNICODE

>>> d = re.match(r"(.+)+","abc\nccc",re.DOTALL)
>>> d.groups()
42: ('abc\nccc',)

>>> re.subn(r"(hello)","\g<1> edisonlz's","hello world")
51: ("hello edisonlz's world", 1)

irb(main):020:0> "edison:lz".gsub(/(\w+):(\w+)/,'\2,\1')
=> "lz,edison"

>>> type(r"dd")
52: 

irb(main):021:0> /dd/.type
=> Regexp

[color=red][b]对Class 的扩展[/b][/color]
python 使用metaclass对类进行扩展（初始化类的类），而ruby 使用 partial class和 mixin 对类进行扩展，python 不支持 partial class 和 mixin的方法,

class ModelBase(type):

    """Metaclass of the Model."""

 def __new__(cls, name, bases, dct):
        return type.__new__(cls, name, bases, dct)

    def __init__(cls, name, bases, attrs):
        """
        intialize name base modle  attribute
        param:
            name:string
            bases:base model
            attrs: attribute
        """
        super(ModelBase, cls).__init__(name, bases, attrs)
        cls._initialize_attributes(cls, name, bases, attrs)
        cls._initialize_manager(cls)

    def _initialize_attributes(self,model_class, name, bases, attrs):
        """
        Initialize the attributes of the model.
        param:
            model_class:object
            name:string
            bases:base model
            attrs:attribute
        """
        #主要功能：添加属性列表
        model_class.attributes = {}
        for k, v in attrs.iteritems():
            if isinstance(v,Attribute):
                    model_class.attributes[k] = v
                    v.name = v.name or k


    def _initialize_manager(self,model_class):
        """
        Initializes the objects manager attribute of the model.
        param:
            model_class:object
        """
        model_class.objects = ModelSet(model_class)
        pass


class Model(object):
    __metaclass__ = ModelBase

class Array  
  def inject(n)  
     each { |value| n = yield(n, value) }  
     n  
  end  
  def sum  
    inject(0) { |n, value| n + value }  
  end  
  def product  
    inject(1) { |n, value| n * value }  
  end  
end  
[ 1, 2, 3, 4, 5 ].sum  » 15  
[ 1, 2, 3, 4, 5 ].product  » 120  

[color=red][b]decorator的应用[/b][/color]
python 使用func decorator 的方法，ruby 使用 yield block的方法和Rails alias_method的方法

>>> _cache = {}
... def cache(sec=10):
...     def wrap(f):
...         def func(*args,**kwargs):
...             data = _cache.get(",".join(args))
...             if not data:
...                 data = f(*args,**kwargs)
...                 _cache[",".join(args)] = data
...                 print "no cache"
...             else:
...                 print "in cache"
...             return data
...         return func
...     return wrap
... 
... @cache(10)
... def page(html):
...     return "response %s" % html
>>> page("haha")
no cache
70: 'response haha'
>>> page("haha")
in cache
71: 'response haha'

class Object
 def memory(name)
         ori = "ori_#{name}" 
         alias_method ori,name

         define_method(name) do
          cache = instance_variable_get("@#{name}")
          if cache
            return cache
          else
            cache =  send(ori)
            instance_variable_set("@#{name}",cache)
            return cache
          end
         end
 end
end 

class A
 def run
   puts "sleeping"      
   sleep 5 
 "a"
 end
 memory(:run)
end  

a = A.new
puts a.run
puts a.run

def select(n)
 t = []
 for i in n
 t.push(i) if yield(i)
  end
return t
  end
=> nil
irb(main):052:0> select([1,2,3]){|i| i>2}
=> [3]

module ActiveRecordExtension
    def self.included(base)
        base.extend(ClassMethods)
        base.class_eval do
            class << self
                p "Aliasing find" # Used to check if alias_method isn't 
called twice
                alias_method :find_without_someting, :find
                alias_method :find, :find_with_someting
            end
        end
    end

    module ClassMethods # :nodoc:
        def find_with_something(*args)
          p "0"
          x = find_without_something(*args)
          p "1"
          return x
        end
    end   
end

ruby还有一个写滴向javascript滴东东

irb(main):015:0> c = "1"
irb(main):015:0> class << c
irb(main):016:1>   def to_ff
irb(main):017:2>     self.to_f
irb(main):018:2>     end
irb(main):019:1>   end
=> nil
irb(main):020:0> c.to_ff
1.0

[color=red][b]lambda的应用[/b][/color]
python和ruby 中都有有lambda，并且意思也都一样，但是python 中没有 proc
ruby 中的 lambda 和 proc 是一个东东
proc { |...| block } => a_proc
lambda { |...| block } => a_proc
---------------------------------------------------------------------------------
Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.

>>> def f(x):
...     return x*2
...     
>>> f(3)
>>> g = lambda x: x*2  
>>> g(3)

>>> g = lambda { |x| x*2  }
>>> g.call(3)

一般情况lambda 表达式与闭包一起应用

def nTimes(aThing)  
  return proc { |n| aThing * n }  
end  

p1 = nTimes(23)  
p1.call(3)  » 69  
p1.call(4)  » 92  
p2 = nTimes("Hello ")  
p2.call(3)  » "Hello Hello Hello "  

python 中滴闭包，这里举个小列子，用于一次完成多个替换

>>> import re
... def mre(dic,text):
...     rc = re.compile("|".join( map( re.escape,dic.keys() ) ) )
...     print rc
...     def get_value(match):
...         return dic.get(match.group(0))
...     return rc.sub(get_value,text)
>>> dic = {"a":"A","b":"B"}
... mre(dic,"abab")
<_sre.SRE_Pattern object at 0x01A8CED0>
115: 'ABAB'

[color=red][b]yield 区别[/b][/color]

在python 中yield 是一个generator 可以保存住当前的context，这一点和ruby 类似，
但是ruby的yield 是调用一个block 也就是调用一个 proc.new {}
我个人编程不习惯使用python的yield

>>> def y(n):
...     for  i in xrange(n):
...         yield i
... for g in y(10):
...     print g ,
0 1 2 3 4 5 6 7 8 9

def any(n)
 t = []
 for i in n
 return true if yield(i)
  end
return false
  end
=> nil
irb(main):052:0> any([0,1,0]){|i|  i!=0}
=>  true

[color=red][b]symbol and tuple[/b][/color]
在python 中建议在传递参数和迭代的时候使用tuple来减少开销
在ruby中大家使用 symbol 来提高访问速度，都是挺好的特性

:edisonlz.id
('edison','lz')

[color=red][b]inheritance[/b][/color]
python 中支持多继承，ruby 不支持多继承但是支持mixin
python 多继承的查找链规则： This is depth-first, left-to-right
ruby 中的查找链规则：self->mixin->super

class Base():
    pass

class Car():
    pass

class BMW(Base,Car):
    pass

ruby中的继承：
in the diagram below, "normal" classes are green, and meta-classes are blue. The dashed lines represent "instance off" (the "klass" pointer), and the solid lines represent "inherits" (the "super" method):

[img]http://www.hokstad.com/static/rom/rom.png[/img]

[color=red][b]block[/b][/color]

The blocks used by iterators (such as loop and each) are a little different. Normally, the local variables created in these blocks are not accessible outside the block. 

[ 1, 2, 3 ].each do |x|
  y = x + 1
end
[ x, y ]


produces: prog.rb:4: undefined local variable or method `x'for # (NameError)

[color=red][b]ruby独有的特性[/b][/color]

What happens when you copy a frozen object? That depends on the method you use. If you call an object's clone method, the entire object state (including whether it is frozen) is copied to the new object. On the other hand, dup typically copies only the object's contents---the new copy will not inherit the frozen status. 

str1 = "hello"  
str1.freeze  » "hello"  
str1.frozen?  » true  
str2 = str1.clone  
str2.frozen?  » true  
str3 = str1.dup  
str3.frozen?  » false  

[color=red][b]private protected，和public[/b][/color]
python 中是没有private protected，和public滴
ruby中对private protected，和public是有定义滴，并且能对定义重载

>>> class Base(object):
...     def __p(self):
...         print "private"
...     def _prot(self):
...         print "protected"
...     def p(self):
...         print "public"
>>> b = Base()
>>> b.__p()
Traceback (most recent call last):
  File "", line 1, in 
    b.__p()
AttributeError: 'Base' object has no attribute '__p'
>>> b._prot()
protected
>>> b.p()
public
>>> b._Base__p
0: >
>>> b._Base__p()
private

class Base
  def aMethod
    puts "Got here"
  end
  private :aMethod
end

class Derived1 < Base
  public :aMethod
end

class Derived2 < Base
end

[img]http://edisonlz.iteye.com/upload/picture/pic/90745/af199522-b53c-364e-9665-94c4f94457d3.png[/img]
令人困惑地instance_eval and class_eval

Use ClassName.instance_eval to define class methods.

Use ClassName.class_eval to define instance methods.

That’s right. Not a typo. Here are some examples, shamelessly stolen from his post:

1
# Defining a class method with instance_eval
2
Fixnum.instance_eval { def ten; 10; end }
3
Fixnum.ten #=> 10
4

5
# Defining an instance method with class_eval
6
Fixnum.class_eval { def number; self; end }
7
7.number #=> 7

[color=red][b]method_missing[/b][/color]

ruby 中独有滴methods missing 使得rails更加滴方便

user.find_by_XXX
uesr.find_or_create_by_xxx
当然这些都不神秘，

def method_missing(method_id, *arguments, &block)
          if match = DynamicFinderMatch.match(method_id)
            attribute_names = match.attribute_names
            super unless all_attributes_exists?(attribute_names)
            if match.finder?
class DynamicFinderMatch
    def self.match(method)
      df_match = self.new(method)
      df_match.finder ? df_match : nil
    end

    def initialize(method)
      @finder = :first
      case method.to_s
      when /^find_(all_by|last_by|by)_([_a-zA-Z]\w*)$/
        @finder = :last if $1 == 'last_by'
        @finder = :all if $1 == 'all_by'
        names = $2
      when /^find_by_([_a-zA-Z]\w*)\!$/
        @bang = true
        names = $1
      when /^find_or_(initialize|create)_by_([_a-zA-Z]\w*)$/
        @instantiator = $1 == 'initialize' ? :new : :create
        names = $2
      else
        @finder = nil
      end
      @attribute_names = names && names.split('_and_')
    end

    attr_reader :finder, :attribute_names, :instantiator

    def finder?
      [email protected]? && @instantiator.nil?
    end

    def instantiator?
      @finder == :first && [email protected]?
    end

    def bang?
      @bang
    end
  end

const_missing 也不神秘

class Module
  define_method(:const_missing) do |name|
    name.to_s
  end
A =》 'A'

[color=red][b]查找路径[/b][/color]

python sys.path
ruby $:
rails $LOAD_PATH
$: == $LOAD_PATH

[color=red][b]django 和rails之间的区别[/b][/color]
框架：两种框架都是MVC，

REST: django 对REST 支持的并不好， 不像Rails那面优雅

模板系统：django的模板系统那就是个X，实在受不了，读取模板文件要几百毫秒，但幸运滴是，有jinja2模板系统，使用c写滴，这个很让人满意，rails虽然也有第三方的模板系统但是，与rails版本有关联，这个不大好

Model ： django 使用 objects.filter和objects.get 功能比较少，而且查询关键字比较怪
rails 使用 find，并且支持 select ,where 等字段重写，挺好滴

DB ：目前 django 还不支持db connection poll，需要第三方滴
rails 目前支持 db connection poll

但是除了django 和 rails 相比，python 在其他领域那就比ruby强太多了，
例如：wxpython，tornado，twisted，pypy, cjson, pylibmc，都是被人津津乐道的，ruby 似乎只有rails可以被人津津乐道，杯具啊！


加载环境 rails 和 django 使用的加载环境方法基本一样

rails 加载顺序

  require File.join(File.dirname(__FILE__), 'boot')

  # All that for this:
  Rails.boot!

  def boot!
      unless booted?
        preinitialize
        pick_boot.run
      end
   end

  def preinitialize
      load(preinitializer_path) if File.exist?(preinitializer_path)
  end
  def pick_boot
      (vendor_rails? ? VendorBoot : GemBoot).new
  end

  class Boot
    def run
      load_initializer
      Rails::Initializer.run(:set_load_path)
    end
  end

  class GemBoot < Boot
    def load_initializer
      self.class.load_rubygems
      load_rails_gem
      require 'initializer'
    end
  end

  #   Rails::Initializer.run do |config|
  #     config.frameworks -= [ :action_mailer ]
  #   end

   class Initializer
    def self.run(command = :process, configuration = Configuration.new)
      yield configuration if block_given?
      initializer = new configuration
      initializer.send(command)
      initializer
    end


 def process
      Rails.configuration = configuration

      check_ruby_version
      install_gem_spec_stubs
      set_load_path
      add_gem_load_paths

      require_frameworks
      set_autoload_paths
      add_plugin_load_paths
      load_environment
      preload_frameworks

      initialize_encoding
      initialize_database

      initialize_cache
      initialize_framework_caches

      initialize_logger
      initialize_framework_logging

      initialize_dependency_mechanism
      initialize_whiny_nils

      initialize_time_zone
      initialize_i18n

      initialize_framework_settings
      initialize_framework_views

      initialize_metal

      add_support_load_paths

      check_for_unbuilt_gems

      load_gems
      load_plugins

      # pick up any gems that plugins depend on
      add_gem_load_paths
      load_gems
      check_gem_dependencies

      # bail out if gems are missing - note that check_gem_dependencies will have
      # already called abort() unless $gems_rake_task is set
      return unless gems_dependencies_loaded

      load_application_initializers

      # the framework is now fully initialized
      after_initialize

      # Setup database middleware after initializers have run
      initialize_database_middleware

      # Prepare dispatcher callbacks and run 'prepare' callbacks
      prepare_dispatcher

      # Routing must be initialized after plugins to allow the former to extend the routes
      initialize_routing

      # Observers are loaded after plugins in case Observers or observed models are modified by plugins.
      load_observers

      # Load view path cache
      load_view_paths

      # Load application classes
      load_application_classes

      # Disable dependency loading during request cycle
      disable_dependency_loading

      # Flag initialized
      Rails.initialized = true
    end


     def default_load_paths
        paths = []

        # Add the old mock paths only if the directories exists
        paths.concat(Dir["#{root_path}/test/mocks/#{environment}"]) if File.exists?("#{root_path}/test/mocks/#{environment}")

        # Add the app's controller directory
        paths.concat(Dir["#{root_path}/app/controllers/"])

        # Followed by the standard includes.
        paths.concat %w(
          app
          app/metal
          app/models
          app/controllers
          app/helpers
          app/services
          lib
          vendor
        ).map { |dir| "#{root_path}/#{dir}" }.select { |dir| File.directory?(dir) }

        paths.concat builtin_directories
      end
  return to environment.rb
  proceed......

[color=red][b]在谈一下rack 和 tornado[/b][/color]
tornado是一个lightweight web server
可是rack 比tornado还要 lightweight ，因为tornado 实现了自己的网络层
，rack则使用fastcgi，cgi，mongrel这些现有滴实现
还有ruby 滴sinatra 是rack 滴扩展，但是提倡 minimalist，更少地代码。


对ruby滴扩展

class NilClass
  def try(*args)
   nil
  end
end
=> nil
user = User.find(100)
user ? user.name : nil
user.try(:name)

class Object
def blank?
 return  respond_to?(:empty) ? empty? : !self
end
def present?
!blank?
end
end
=> nil
a = ""
=> ""
a.present?
=> false
a.blank?
=> true

ruby metaprogramming

yes = "yes"
ok = "ok"

String.class_eval do 
 define_method(yes) do
   print ok
 end
end

puts "123".yes #=> ok

#create singleton methods
#String.class_eval do

# class << self 
#         define_method(yes) do
#           print ok
#         end
# end
#end

#puts String.yes 

#C:/Users/liuzheng/Desktop/a.rb:46:in `singletonclass': undefined local variable
#or method `yes' for # (NameError)
#        from C:/Users/liuzheng/Desktop/a.rb:45:in `block in 
'
#        from C:/Users/liuzheng/Desktop/a.rb:44:in `class_eval'
#        from C:/Users/liuzheng/Desktop/a.rb:44:in `
'

#because class << self has new scope

yes = "yes"
ok = "ok"
metaclass = (class <metaclass.class_eval do
  define_method(yes) do  
   puts ok
 end
end
puts String.yes => "ok"

[img]http://edisonlz.iteye.com/upload/picture/pic/90742/46ba63a5-8987-375d-aac9-6d2f847ce5b2.png[/img]