optionally, cache page text until next edit operation

If 'cache' is set to True on init, store the results of
page.text() operations in a simple cache dict. This avoids
unnecessary remote roundtrips. Cache is cleared on each
successful page.save() operation.

page.text() has its own 'cache' argument which, if set to
True or False, overrides whatever the instance setting is.
We might consider also clearing the cache if the instance
setting is True but text() is called with cache set False.

mwclient/page.py

@@ -10,12 +10,14 @@
 
 class Page(object):
 
-    def __init__(self, site, name, info=None, extra_properties={}):
+    def __init__(self, site, name, info=None, extra_properties={}, cache=False):
         if type(name) is type(self):
             return self.__dict__.update(name.__dict__)
         self.site = site
         self.name = name
         self.section = None
+        self.cache = cache
+        self._textcache = {}
 
         if not info:
             if extra_properties:
@@ -110,20 +112,24 @@ def get_expanded(self):
 
         return self.text(expandtemplates=True)
 
-    def edit(self, *args, **kwargs):
+    def edit(self, section=None, *args, **kwargs):
         """Deprecated. Use page.text() instead"""
         warnings.warn("page.edit() was deprecated in mwclient 0.7.0, please use page.text() instead.",
                       category=DeprecationWarning, stacklevel=2)
-        return self.text(*args, **kwargs)
+        if section:
+            self.section = section
+        return self.text(section, *args, **kwargs)
 
-    def text(self, section=None, expandtemplates=False):
+    def text(self, section=None, expandtemplates=False, cache=None):
         """
         Returns the current wikitext of the page, or of a specific section.
         If the page does not exist, an empty string is returned.
 
         :Arguments:
           - `section` : numbered section or `None` to get the whole page (default: `None`)
           - `expandtemplates` : set to `True` to expand templates (default: `False`)
+          - `cache` : set to `True` or `False` to override the instance cache setting
+            (default: `None`, respect instance setting)
         """
 
         if not self.can('read'):
@@ -132,19 +138,30 @@ def text(self, section=None, expandtemplates=False):
             return u''
         if section is not None:
             section = text_type(section)
+        if cache is None:
+            cache = self.cache
 
-        revs = self.revisions(prop='content|timestamp', limit=1, section=section, expandtemplates=expandtemplates)
-        try:
-            rev = revs.next()
-            text = rev['*']
+        key = (section, expandtemplates)
+        if cache and key in self._textcache:
+            text = self._textcache[key]
+        else:
+            revs = self.revisions(prop='content|timestamp', limit=1, section=section, expandtemplates=expandtemplates)
+            try:
+                rev = revs.next()
+                text = rev['*']
+                self.last_rev_time = rev['timestamp']
+            except StopIteration:
+                text = u''
+                self.last_rev_time = None
+            if not expandtemplates:
+                self.edit_time = time.gmtime()
+
+        if cache:
+            self._textcache[key] = text
+        if text:
             self.section = section
-            self.last_rev_time = rev['timestamp']
-        except StopIteration:
-            text = u''
+        else:
             self.section = None
-            self.last_rev_time = None
-        if not expandtemplates:
-            self.edit_time = time.gmtime()
         return text
 
     def save(self, text, summary=u'', minor=False, bot=True, section=None, **kwargs):
@@ -206,6 +223,8 @@ def do_edit():
         # 'newtimestamp' is not included if no change was made
         if 'newtimestamp' in result['edit'].keys():
             self.last_rev_time = client.parse_timestamp(result['edit'].get('newtimestamp'))
+        # clear the page text cache
+        self._textcache = {}
         return result['edit']
 
     def handle_edit_error(self, e, summary):