学习pyyaml

网上查了一圈，觉得较好的yaml教程有：

YAML 语言教程 ：http://www.ruanyifeng.com/blog/2016/07/yaml.html。

另外，在github的pyyaml库中找到一个示例：

 #
 # Examples from the Preview section of the YAML specification
 # (http://yaml.org/spec/1.2/#Preview)
 #

 # Sequence of scalars 数组
 ---
 - Mark McGwire
 - Sammy Sosa
 - Ken Griffey

 # Mapping scalars to scalars 字典
 ---
 hr:      # Home runs
 avg: 0.278 # Batting average
 rbi:    # Runs Batted In

 # Mapping scalars to sequences 键为字符串，值为数组的字典
 ---
 american:
   - Boston Red Sox
   - Detroit Tigers
   - New York Yankees
 national:
   - New York Mets
   - Chicago Cubs
   - Atlanta Braves

 # Sequence of mappings 项为字典的数组
 ---
 -
   name: Mark McGwire
   hr:
   avg:  0.278
 -
   name: Sammy Sosa
   hr:
   avg:  0.288

 # Sequence of sequences 项为数组的数组
 ---
 - [name        , hr, avg  ]
 - [Mark McGwire, , 0.278]
 - [Sammy Sosa  , , 0.288]

 # Mapping of mappings 字典套构
 ---
 Mark McGwire: {hr: , avg: 0.278}
 Sammy Sosa: {
     hr: ,
     avg: 0.288
   }

 # Two documents in a stream
 --- # Ranking of  home runs
 - Mark McGwire
 - Sammy Sosa
 - Ken Griffey
 --- # Team ranking
 - Chicago Cubs
 - St Louis Cardinals

 # Documents with the end indicator
 ---
 time: ::
 player: Sammy Sosa
 action: strike (miss)
 ...
 ---
 time: ::
 player: Sammy Sosa
 action: grand slam
 ...

 # Comments
 ---
 hr: #  hr ranking
   - Mark McGwire
   - Sammy Sosa
 rbi:
   #  rbi ranking
   - Sammy Sosa
   - Ken Griffey

 # Anchors and aliases
 ---
 hr:
   - Mark McGwire
   # Following node labeled SS
   - &SS Sammy Sosa
 rbi:
   - *SS # Subsequent occurrence
   - Ken Griffey

 # Mapping between sequences
 ---
 ? - Detroit Tigers
   - Chicago cubs
 :
   - --
 ? [ New York Yankees,
     Atlanta Braves ]
 : [ --, --,
     -- ]

 # Inline nested mapping
 ---
 # products purchased
 - item    : Super Hoop
   quantity:
 - item    : Basketball
   quantity:
 - item    : Big Shoes
   quantity: 

 # Literal scalars
 --- | # ASCII art
   \//||\/||
   // ||  ||__

 # Folded scalars
 --- >
   Mark McGwire's
   year was crippled
   by a knee injury.

 # Preserved indented block in a folded scalar
 ---
 >
  Sammy Sosa completed another
  fine season with great stats.

     Home Runs
    0.288 Batting Average

  What a year!

 # Indentation determines scope
 ---
 name: Mark McGwire
 accomplishment: >
   Mark set a major league
   home run record in .
 stats: |
    Home Runs
   0.278 Batting Average
 # Quoted scalars
 ---
 unicode: "Sosa did fine.\u263A"
 control: "\b1998\t1999\t2000\n"
 hex esc: "\x0d\x0a is \r\n"
 single: '"Howdy!" he cried.'
 quoted: ' # not a ''comment''.'
 tie-fighter: '|\-*-/|'

 # Multi-line flow scalars
 ---
 plain:
   This unquoted scalar
   spans many lines.
 quoted: "So does this
   quoted scalar.\n"

 # Integers
 ---
 canonical:
 decimal: +12_345
 sexagesimal: ::
 octal:
 hexadecimal: 0xC

 # Floating point
 ---
 canonical: 1.23015e+3
 exponential: 12.3015e+02
 sexagesimal: :30.15
 fixed: 1_230.
 negative infinity: -.inf
 not a number: .NaN

 # Miscellaneous
 ---
 null: ~
 true: boolean
 false: boolean
 string: ''

 # Timestamps
 ---
 canonical: --15T02::.1Z
 iso8601: --14t21::43.10-:
 spaced: -- ::43.10 -
 date: --

 # Various explicit tags
 ---
 not-date: !!str --
 picture: !!binary |
  R0lGODlhDAAMAIQAAP//9/X
  17unp5WZmZgAAAOfn515eXv
  Pz7Y6OjuDg4J+fn5OTk6enp
  56enmleECcgggoBADs=
 application specific tag: !something |
  The semantics of the tag
  above may be different for
  different documents.
 # Global tags
 %TAG ! tag:clarkevans.com,:
 --- !shape
   # Use the ! handle for presenting
   # tag:clarkevans.com,:circle
 - !circle
   center: &ORIGIN {x: , y: }
   radius:
 - !line
   start: *ORIGIN
   finish: { x: , y:  }
 - !label
   start: *ORIGIN
   color: 0xFFEEBB
   text: Pretty vector drawing.

 # Unordered sets
 --- !!set
 # sets are represented as a
 # mapping where each key is
 # associated with the empty string
 ? Mark McGwire
 ? Sammy Sosa
 ? Ken Griff

 # Ordered mappings
 --- !!omap
 # ordered maps are represented as
 # a sequence of mappings, with
 # each mapping having one key
 - Mark McGwire:
 - Sammy Sosa:
 - Ken Griffy: 

 # Full length example
 --- !<tag:clarkevans.com,:invoice>
 invoice:
 date   : --
 bill-to: &id001
     given  : Chris
     family : Dumars
     address:
         lines: |
              Walkman Dr.
             Suite #
         city    : Royal Oak
         state   : MI
         postal  :
 ship-to: *id001
 product:
     - sku         : BL394D
       quantity    :
       description : Basketball
       price       : 450.00
     - sku         : BL4438H
       quantity    :
       description : Super Hoop
       price       : 2392.00
 tax  : 251.42
 total: 4443.52
 comments:
     Late afternoon is best.
     Backup contact is Nancy
     Billsmer @ -.

 # Another full-length example
 ---
 Time: -- :: -
 User: ed
 Warning:
   This is an error message
   for the log file
 ---
 Time: -- :: -
 User: ed
 Warning:
   A slightly different error
   message.
 ---
 Date: -- :: -
 User: ed
 Fatal:
   Unknown variable "bar"
 Stack:
   - file: TopClass.py
     line:
     code: |
       x = MoreObject("345\n")
   - file: MoreClass.py
     line:
     code: |-
       foo = bar

英文不太好，很多不太会翻译。就不误导别人了，见谅。