diff -r 842147eb1b26 Lib/textwrap.py
--- a/Lib/textwrap.py	Mon Jul 04 19:11:14 2011 -0700
+++ b/Lib/textwrap.py	Mon Jul 04 22:59:22 2011 -0400
@@ -33,6 +33,9 @@
       width (default: 70)
         the maximum width of wrapped lines (unless break_long_words
         is false)
+      width_func (default: len)
+        function to use to identify the length of a string of text.
+        Overridden if the font being used has different character widths.
       initial_indent (default: "")
         string that will be prepended to the first line of wrapped
         output.  Counts towards the line's width.
@@ -95,6 +98,7 @@
 
     def __init__(self,
                  width=70,
+                 width_func=len,
                  initial_indent="",
                  subsequent_indent="",
                  expand_tabs=True,
@@ -104,6 +108,7 @@
                  drop_whitespace=True,
                  break_on_hyphens=True):
         self.width = width
+        self.width_func = width_func
         self.initial_indent = initial_indent
         self.subsequent_indent = subsequent_indent
         self.expand_tabs = expand_tabs
@@ -239,7 +244,7 @@
                 indent = self.initial_indent
 
             # Maximum width for this line.
-            width = self.width - len(indent)
+            width = self.width - self.width_func(indent)
 
             # First chunk on line is whitespace -- drop it, unless this
             # is the very beginning of the text (ie. no lines started yet).
@@ -247,7 +252,7 @@
                 del chunks[-1]
 
             while chunks:
-                l = len(chunks[-1])
+                l = self.width_func(chunks[-1])
 
                 # Can at least squeeze this chunk onto the current line.
                 if cur_len + l <= width:
@@ -260,7 +265,7 @@
 
             # The current line is full, and the next chunk is too big to
             # fit on *any* line (not just this one).
-            if chunks and len(chunks[-1]) > width:
+            if chunks and self.width_func(chunks[-1]) > width:
                 self._handle_long_word(chunks, cur_line, cur_len, width)
 
             # If the last chunk on this line is all whitespace, drop it.