本文共 9100 字，大约阅读时间需要 30 分钟。
其实也无需了解得太深入，但是至少你得知道一个 yaml 文件在 Ruby 里加载成 Hash，或者在 Python 里加载成字典以后会是什么样子。看例子学习是最好不过的了。
细节请参考：（虽然是英文，但是图文并茂，看起来丝毫不会有障碍）。
1、使用空白字符为文件缩进来表示结构；不过不能使用跳格字符 (TAB)。
2、注解由井字号（ # ）开始，可以出现在一行中的任何位置，而且范围只有一行（也就是一般所谓的单行注释） 3、每个清单成员以单行表示，并用短杠 + 空白（ - ）起始。或使用方括号（ [ ] ），并用逗号 + 空白（ , ）分开成员。 4、每个散列表的成员用冒号 + 空白（ : ）分开键值和内容。或使用大括号（ { } ），并用逗号 + 空白（ , ）分开。 5、散列表的键值可以用问号 ( ? ) 起始，用来明确的表示多个词汇组成的键值。 6、字符串平常并不使用引号，但必要的时候可以用双引号 ( " ) 或单引号 ( ' ) 框住。 7、使用双引号表示字符串时，可用倒斜线（ \ ）开始的转义字符（这跟 C 语言类似）表示特殊字符。 8、区块的字符串用缩进和修饰符（非必要）来和其他数据分隔，有保存新行（preserve）（使用符号 | ）或折叠新行（flod）（使用符号 > ）两种方式。 9、在单一文件中，可用连续三个连字号（---）区分多个文件。 10、另外，还有选择性的连续三个点号（ ... ）用来表示文件结尾。 11、重复的内容可使从参考标记星号 ( * ) 复制到锚点标记（ & ）。 12、指定格式可以使用两个惊叹号 ( !! )，后面接上名称。 13、文件中的单一文件可以使用指导指令，使用方法是百分比符号 ( % )。有两个指导指令在 YAML1.1 版中被定义： % YAML 指导指令，用来识别文件的 YAML 版本。 % TAG 指导指令，被用在 URI 的前缀标记。这个方法在标记节点的类型时相当有用。 14、YAML 在使用逗号及冒号时，后面都必须接一个空白字符，所以可以在字符串或数值中自由加入分隔符号（例如：5,280 或 ）而不需要使用引号。另外还有两个特殊符号在 YAML 中被保留，有可能在未来的版本被使用 --（ @ ）和（ ` ）。
# Rubyrequire 'yaml'puts YAML.load_file("test.yaml").inspect # test.yamlreceipt: Oz-Ware Purchase Invoicedate: 2012-08-06customer: given: Dorothy family: Galeitems: - part_no: A4786 descrip: Water Bucket (Filled) price: 1.47 quantity: 4 - part_no: E1628 descrip: High Heeled "Ruby" Slippers size: 8 price: 133.7 quantity: 1bill-to: &id001 street: | 123 Tornado Alley Suite 16 city: East Centerville state: KSship-to: *id001specialDelivery: > Follow the Yellow Brick Road to the Emerald City. Pay no attention to the man behind the curtain.
# Hash{"receipt"=>"Oz-Ware Purchase Invoice", "date"=># , "customer"=>{"given"=>"Dorothy", "family"=>"Gale"}, "items"=> [{"part_no"=>"A4786", "descrip"=>"Water Bucket (Filled)", "price"=>1.47, "quantity"=>4}, {"part_no"=>"E1628", "descrip"=>"High Heeled \"Ruby\" Slippers", "size"=>8, "price"=>133.7, "quantity"=>1}], "bill-to"=> {"street"=>"123 Tornado Alley\n" + "Suite 16\n", "city"=>"East Centerville", "state"=>"KS"}, "ship-to"=> {"street"=>"123 Tornado Alley\n" + "Suite 16\n", "city"=>"East Centerville", "state"=>"KS"}, "specialDelivery"=> "Follow the Yellow Brick Road to the Emerald City. Pay no attention to the man behind the curtain."} # Yaml - Casablanca- North by Northwest- Notorious
# Ruby["Casablanca", "North by Northwest", "Notorious"]
# Yaml seq: [ a, b, c ]
# Ruby{"seq"=>["a", "b", "c"]} # Yaml- - foo - bar - baz
# Ruby[["foo", "bar", "baz"]]
# Yaml- apple - - foo - bar - x123 - banana - carrot
# Ruby["apple", ["foo", "bar", "x123"], "banana", "carrot"]
# Yaml- - - uno - dos
# Ruby[[["uno", "dos"]]]
# Yamlname: John Smithage: 33
# Ruby{"name"=>"John Smith", "age"=>33} # Yamlhash: { name: Steve, foo: bar } # Ruby{"hash"=>{"name"=>"Steve", "foo"=>"bar"}} # Yamlfoo: whatever bar: - uno - dos
# Ruby{"foo"=>"whatever", "bar"=>["uno", "dos"]} # Yamlfoo: whatever bar: fruit: apple name: steve sport: baseball
# Ruby{"foo"=>"whatever", "bar"=>{"fruit"=>"apple", "name"=>"steve", "sport"=>"baseball"}} # Yamlfoo: whateverbar: - fruit: apple name: steve sport: baseball - more - python: rocks perl: papers ruby: scissorses
# Ruby{"foo"=>"whatever", "bar"=>[{"fruit"=>"apple", "name"=>"steve", "sport"=>"baseball"}, "more", {"python"=>"rocks", "perl"=>"papers", "ruby"=>"scissorses"}]} # Yaml- work on YAML.py: - work on Store
# Ruby[{"work on YAML.py"=>["work on Store"]}] # Yamlallow: - 'localhost' - '%.sourceforge.net' - '%.freepan.org'
# Ruby{"allow"=>["localhost", "%.sourceforge.net", "%.freepan.org"]} # Yamlmapping: name: Joe job: Accountant <<: age: 38
# Ruby{"mapping"=>{"name"=>"Joe", "job"=>"Accountant", "age"=>38}} # Yamllanguages: [ Ruby, Perl, Python ]websites: { YAML: yaml.org, Ruby: ruby-lang.org, Python: python.org, Perl: use.perl.org } # Ruby{"languages"=>["Ruby", "Perl", "Python"], "websites"=>{"YAML"=>"yaml.org", "Ruby"=>"ruby-lang.org", "Python"=>"python.org", "Perl"=>"use.perl.org"}} # Yaml--- String
# Ruby"String"
# Yaml- What's Yaml?- It's for writing data structures in plain text.- And?- And what? That's not good enough for you?- No, I mean, "And what about Yaml?"- Oh, oh yeah. Uh.. Yaml for Ruby.
# Ruby["What's Yaml?", "It's for writing data structures in plain text.", "And?", "And what? That's not good enough for you?", "No, I mean, \"And what about Yaml?\"", "Oh, oh yeah. Uh.. Yaml for Ruby."]
# Yamlthe colon followed by space is an indicator: but is a string:right heresame for the pound sign: here we have it#in a stringthe comma can, honestly, be used in most cases: [ but not in, inline collections ]
# Ruby{"the colon followed by space is an indicator"=>"but is a string:right here", "same for the pound sign"=>"here we have it#in a string", "the comma can, honestly, be used in most cases"=>["but not in", "inline collections"]} # Yamldate string: !str 2001-08-01number string: !str 192
# Ruby{"date string"=>"2001-08-01", "number string"=>"192"} # Yamlall my favorite symbols: '#:!/%.)'a few i hate: '&(*'why do i hate them?: 'it''s very hard to explain'
# Ruby{"all my favorite symbols"=>"#:!/%.)", "a few i hate"=>"&(*", "why do i hate them?"=>"it's very hard to explain"} # Yamli know where i want my line breaks: "one here\nand another here\n"
# Ruby{"i know where i want my line breaks"=>"one here\nand another here\n"} # Yamli want a long string: "so i'm going to let it go on and on to other lines until i end it with a quote."
# Ruby{"i want a long string"=>"so i'm going to let it go on and on to other lines until i end it with a quote."} # Yamlname: Mr. Showhosted by: Bob and Daviddate of next season: ~
# Ruby{"name"=>"Mr. Show", "hosted by"=>"Bob and David", "date of next season"=>nil} # YamlIs Gus a Liar?: trueDo I rely on Gus for Sustenance?: false
# Ruby{"Is Gus a Liar?"=>true, "Do I rely on Gus for Sustenance?"=>false} # Yamlzero: 0simple: 12one-thousand: 1,000negative one-thousand: -1,000
# Ruby{"zero"=>0, "simple"=>12, "one-thousand"=>1000, "negative one-thousand"=>-1000} # Yaml1: one 2: two 3: three
# Ruby{1=>"one", 2=>"two", 3=>"three"} # Yamla simple float: 2.00larger float: 1,000.09scientific notation: 1.00009e+3
# Ruby{"a simple float"=>2.0, "larger float"=>1000.09, "scientific notation"=>1000.09} # Yamliso8601: 2001-12-14t21:59:43.10-05:00space seperated: 2001-12-14 21:59:43.10 -05:00
# Ruby{"iso8601"=>2001-12-15 10:59:43 +0800, "space seperated"=>2001-12-15 10:59:43 +0800} # Yaml--- 1976-07-31
# Ruby#
YAML 的自动判定数据形态是哪一种实体。但有时用户会想要将数据强制转型成自定的某种类型。最常见的状况是字符串，有时候可能看起来像数字或布尔值，这种时候可以使用双引号，或是使用严格类型标签。
# Yaml---a: 123 # 整数b: "123" # 字串（使用双引号）c: 123.0 # 浮点数d: !!float 123 # 浮点数，使用!!表示的严格类型e: !!str 123 # 字串，使用严格类型f: !!str Yes # 字串，使用严格类型g: Yes # 布尔值"真"h: Yes we have No bananas # 字串（包含"Yes"和"No"）
# Ruby{"a"=>123, "b"=>"123", "c"=>123.0, "d"=>123.0, "e"=>"123", "f"=>"Yes", "g"=>true, "h"=>"Yes we have No bananas"} # Yamldata: | Wrapped text # 折叠的文字 will be folded # 将会被收 into a single # 进单一一个 paragraph # 段落 Blank lines denote # 空白的行代表 paragraph breaks # 段落直接的间隔
# Ruby{"data"=> "Wrapped text # 折叠的文字\n" + "will be folded # 将会被收\n" + "into a single # 进单一一个\n" + "paragraph # 段落\n" + "\n" + "Blank lines denote # 空白的行代表\n" + "paragraph breaks # 段落直接的间隔"} # Yamldata: > Wrapped text # 折叠的文字 will be folded # 将会被收 into a single # 进单一一个 paragraph # 段落 Blank lines denote # 空白的行代表 paragraph breaks # 段落直接的间隔
# Ruby{"data"=> "Wrapped text # 折叠的文字 will be folded # 将会被收 into a single # 进单一一个 paragraph # 段落\n" + "Blank lines denote # 空白的行代表 paragraph breaks # 段落直接的间隔"} 和保存新行不同的是，换行字符会被转换成空白字符。而引领空白字符则会被自动消去。
有点类似于大部分语言当中类的定义和继承的关系，如果定义有冲突，以子类的为准。
# Yaml---- step: &id001 # 锚点标签标签 &id001 instrument: Lasik 2000 pulseEnergy: 5.4 pulseDuration: 12 repetition: 1000 spotSize: 1mm- step: <<: *id001 # 合并键值：使用在锚点标签定义的內容 spotSize: 2mm #- step: <<: *id001 # 合并键值：使用在锚点标签定义的內容 pulseEnergy: 500.0 # 覆盖键值 alert: > # 加入其他键值 warn patient of audible pop
# Ruby[{"step"=> {"instrument"=>"Lasik 2000", "pulseEnergy"=>5.4, "pulseDuration"=>12, "repetition"=>1000, "spotSize"=>"1mm"}}, {"step"=> {"instrument"=>"Lasik 2000", "pulseEnergy"=>5.4, "pulseDuration"=>12, "repetition"=>1000, "spotSize"=>"2mm"}}, {"step"=> {"instrument"=>"Lasik 2000", "pulseEnergy"=>500.0, "pulseDuration"=>12, "repetition"=>1000, "spotSize"=>"1mm", "alert"=>"warn patient of audible pop"}}] 转载地址：http://gcjqi.baihongyu.com/