Documentation.

[python-bulletml.git] / bulletml / parser.py

diff --git a/bulletml/parser.py b/bulletml/parser.py
index edb9d29..62f00d4 100644 (file)
--- a/bulletml/parser.py
+++ b/bulletml/parser.py
@@ -1,6 +1,10 @@
 """BulletML parser.
 
-http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/index_e.html
+This is based on the format described at
+http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/bulletml_ref_e.html.
+
+Unless you are adding support for new tags, the only class you should
+care about in here is BulletML.
 """
 
 from __future__ import division
@@ -31,7 +35,7 @@ def realtag(element):
 class ParamList(object):
     """List of parameter definitions."""
 
-    def __init__(self, params=[]):
+    def __init__(self, params=()):
         self.params = list(params)
 
     @classmethod
@@ -312,7 +316,13 @@ class BulletRef(object):
             type(self).__name__, self.params, self.bullet)
 
 class ActionDef(object):
-    """Action definition."""
+    """Action definition.
+
+    To support parsing new actions, add tags to
+    ActionDef.CONSTRUCTORS. It maps tag names to classes with a
+    FromElement classmethod, which take the BulletML instance and
+    ElementTree element as arguments.
+    """
 
     # This is self-referential, so it's filled in later.
     CONSTRUCTORS = dict()
@@ -435,6 +445,12 @@ class BulletML(object):
 
     A BulletML document is a collection of bullets, actions, and
     firings, as well as a base game type.
+
+    You can add tags to the BulletML.CONSTRUCTORS dictionary to extend
+    its parsing. It maps tag names to classes with a FromElement
+    classmethod, which take the BulletML instance and ElementTree
+    element as arguments.
+    
     """
 
     CONSTRUCTORS = dict(
@@ -443,14 +459,15 @@ class BulletML(object):
         fire=FireDef,
         )
 
-    def __init__(self, type="none", bullets={}, fires={}, actions={}):
+    def __init__(self, type="none", bullets=None, fires=None, actions=None):
         self.type = type
-        self.bullets = {}
-        self.actions = {}
-        self.fires = {}
+        self.bullets = {} if bullets is None else bullets
+        self.actions = {} if actions is None else actions
+        self.fires = {} if fires is None else fires
 
     @classmethod
     def FromDocument(cls, source):
+        """Return a BulletML instance based on a string or file-like."""
         if isinstance(source, (str, unicode)):
             source = StringIO(source)