Use io.BytesIO instead of StringIO

On Python 3, StringIO is for strings.

Author: bgilbert

examples/deepzoom/deepzoom_server.py

@@ -18,8 +18,8 @@
 # Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #
 
-from cStringIO import StringIO
 from flask import Flask, abort, make_response, render_template, url_for
+from io import BytesIO
 from openslide import ImageSlide, open_slide
 from openslide.deepzoom import DeepZoomGenerator
 from optparse import OptionParser
@@ -95,7 +95,7 @@ def tile(slug, level, col, row, format):
     except ValueError:
         # Invalid level or coordinates
         abort(404)
-    buf = StringIO()
+    buf = BytesIO()
     tile.save(buf, format, quality=app.config['DEEPZOOM_TILE_QUALITY'])
     resp = make_response(buf.getvalue())
     resp.mimetype = 'image/%s' % format

openslide/deepzoom.py

@@ -24,7 +24,7 @@
 """
 
 from __future__ import division
-import cStringIO as StringIO
+from io import BytesIO
 import math
 import openslide
 from PIL import Image
@@ -209,6 +209,6 @@ def get_dzi(self, format):
         w, h = self._l0_dimensions
         SubElement(image, 'Size', Width=str(w), Height=str(h))
         tree = ElementTree(element=image)
-        buf = StringIO.StringIO()
+        buf = BytesIO()
         tree.write(buf, encoding='UTF-8')
-        return unicode(buf.getvalue(), 'UTF-8')
+        return buf.getvalue().decode()