Fix graph IO to properly address unicode strings

src/graph/graph_io.cc

@@ -94,11 +94,7 @@ public:
     std::streamsize read(char* s, std::streamsize n)
     {
         boost::python::object pbuf = _file.attr("read")(n);
-#if (PY_MAJOR_VERSION >= 3)
-        string buf = boost::python::extract<string>(pbuf.attr("decode")("utf-8"));
-#else
         string buf = boost::python::extract<string>(pbuf);
-#endif
         for (size_t i = 0; i < buf.size(); ++i)
             s[i] = buf[i];
         return buf.size();
@@ -107,8 +103,15 @@ public:
     std::streamsize write(const char* s, std::streamsize n)
     {
         string buf(s, s+n);
-        boost::python::object pbuf(buf);
-        _file.attr("write")(pbuf.attr("encode")("utf-8"));
+#if (PY_MAJOR_VERSION >= 3)
+        // in python 3 we need to construct a 'bytes' instance
+        PyObject* bytes = PyBytes_FromStringAndSize(s, n);
+        boost::python::handle<> x(bytes);
+        boost::python::object pbuf(x);
+#else
+        boost::python::str pbuf(buf);
+#endif
+        _file.attr("write")(pbuf);
         return n;
     }
 

src/graph_tool/__init__.py

@@ -109,7 +109,7 @@ import gzip
 import weakref
 import copy
 
-from io import BytesIO
+from io import BytesIO, StringIO
 from .decorators import _wraps, _require, _attrs, _limit_args
 from inspect import ismethod
 
@@ -1982,7 +1982,7 @@ class Graph(object):
     def __getstate__(self):
         state = dict()
         sio = BytesIO()
-        stream = gzip.GzipFile(fileobj=sio, mode="wb")
+        stream = gzip.open(sio, mode="wb")
         self.save(stream, "xml")
         stream.close()
         state["blob"] = sio.getvalue()
@@ -1993,7 +1993,7 @@ class Graph(object):
         blob = state["blob"]
         if blob != "":
             sio = BytesIO(blob)
-            stream = gzip.GzipFile(fileobj=sio, mode="rb")
+            stream = gzip.open(sio, mode="rb")
             self.load(stream, "xml")