bulletml/bulletyaml.py

   1 """BulletYAML implementation.
   2
   3 BulletYAML is a translation of BulletML into YAML. The structure is
   4 mostly the same as the XML version, except BulletRef/FireRef/ActionRef
   5 elements are only used if they contain parameters, as YAML has its own
   6 intra-document references. Parameterless references are turned into
   7 direct YAML references.
   8
   9 If PyYAML is installed, importing this module automatically registers
  10 BulletYAML tags with the default loader and dumper.
  11
  12 Example BulletYAML document:
  13     !BulletML
  14     type: vertical
  15     actions:
  16       top: !ActionDef
  17         actions:
  18         - !FireDef
  19           bullet: !BulletDef {}
  20
  21 """
  22
  23 from bulletml import parser
  24
  25 def register(Loader=None, Dumper=None):
  26     """Register BulletYAML types for a Loader and Dumper."""
  27     for cls in [parser.Direction, parser.ChangeDirection,
  28                 parser.Speed, parser.ChangeSpeed, parser.Wait,
  29                 parser.Tag, parser.Untag, parser.Vanish,
  30                 parser.Repeat, parser.Accel, parser.BulletDef,
  31                 parser.BulletRef, parser.ActionDef, parser.ActionRef,
  32                 parser.FireDef, parser.FireRef, parser.Offset,
  33                 parser.BulletML]:
  34
  35         def add(cls, loader, dumper):
  36             """Register a class in a new variable scope."""
  37             tag = "!" + cls.__name__
  38             if loader:
  39                 def construct(loader, node):
  40                     """Construct an object."""
  41                     return loader.construct_yaml_object(node, cls)
  42                 loader.add_constructor(tag, construct)
  43             if dumper:
  44                 def represent(dumper, obj):
  45                     """Represent an object."""
  46                     return dumper.represent_yaml_object(tag, obj, cls)
  47                 dumper.add_representer(cls, represent)
  48
  49         add(cls, Loader, Dumper)
  50
  51 try:
  52     import yaml
  53 except ImportError:
  54     pass
  55 else:
  56     register(yaml, yaml)