Make cython compatible with python3 (#12)

nnvm/Makefile

@@ -3,7 +3,7 @@ export CFLAGS =  -std=c++11 -Wall -O3 -msse2  -Wno-unknown-pragmas -funroll-loop
 	 -Iinclude -Idmlc-core/include -fPIC
 
 # specify tensor path
-.PHONY: clean all test lint doc cython cython3
+.PHONY: clean all test lint doc cython cython3 cyclean
 
 all: lib/libnnvm.so lib/libnnvm.a cli_test
 
@@ -37,6 +37,8 @@ cython:
 cython3:
 	cd python; python3 setup.py build_ext --inplace
 
+cyclean:
+	rm -rf python/nnvm/*/*.so python/nnvm/*/*.cpp
 
 lint:
 	python2 dmlc-core/scripts/lint.py nnvm cpp include src

nnvm/python/nnvm/cython/base.pyi

@@ -9,6 +9,21 @@ cdef py_str(const char* x):
         return x.decode("utf-8")
 
 
+cdef c_str(pystr):
+    """Create ctypes char * from a python string
+    Parameters
+    ----------
+    string : string type
+        python string
+
+    Returns
+    -------
+    str : c_char_p
+        A char pointer that can be passed to C API
+    """
+    return pystr.encode("utf-8")
+
+
 cdef CALL(int ret):
     if ret != 0:
         raise NNVMError(NNGetLastError())
@@ -20,6 +35,13 @@ cdef const char** CBeginPtr(vector[const char*]& vec):
     else:
         return NULL
 
+cdef vector[const char*] SVec2Ptr(vector[string]& vec):
+    cdef vector[const char*] svec
+    svec.resize(vec.size())
+    for i in range(vec.size()):
+        svec[i] = vec[i].c_str()
+    return svec
+
 
 cdef BuildDoc(nn_uint num_args,
               const char** arg_names,

nnvm/python/nnvm/cython/symbol.pyx

@@ -6,6 +6,7 @@ from .._base import NNVMError
 from ..name import NameManager
 from ..attribute import AttrScope
 from libcpp.vector cimport vector
+from libcpp.string cimport string
 from cpython.version cimport PY_MAJOR_VERSION
 
 include "./base.pyi"
@@ -110,7 +111,7 @@ cdef class Symbol:
         CALL(NNSymbolGetOutput(self.handle, c_index, &handle))
         return NewSymbol(handle)
 
-    def attr(self, const char* key):
+    def attr(self, key):
         """Get attribute string from the symbol, this function only works for non-grouped symbol.
 
         Parameters
@@ -125,6 +126,8 @@ cdef class Symbol:
         """
         cdef const char* ret
         cdef int success
+        key = c_str(key)
+
         CALL(NNSymbolGetAttr(
             self.handle, key, &ret, &success))
         if success != 0:
@@ -203,16 +206,19 @@ cdef class Symbol:
     def debug_str(self):
         cdef const char* out_str
         CALL(NNSymbolPrint(self.handle, &out_str))
-        return str(out_str)
+        return py_str(out_str)
 
 
 cdef SymbolSetAttr(SymbolHandle handle, dict kwargs):
-    cdef vector[const char*] param_keys
-    cdef vector[const char*] param_vals
+    cdef vector[string] sparam_keys
+    cdef vector[string] sparam_vals
     cdef nn_uint num_args
     for k, v in kwargs.items():
-        param_keys.push_back(k)
-        param_vals.push_back(str(v))
+        sparam_keys.push_back(c_str(k))
+        sparam_vals.push_back(c_str(str(v)))
+    # keep strings in vector
+    cdef vector[const char*] param_keys = SVec2Ptr(sparam_keys)
+    cdef vector[const char*] param_vals = SVec2Ptr(sparam_vals)
     num_args = param_keys.size()
     CALL(NNSymbolSetAttrs(
         handle, num_args, CBeginPtr(param_keys), CBeginPtr(param_vals)))
@@ -225,7 +231,7 @@ cdef NewSymbol(SymbolHandle handle):
     return sym
 
 
-def Variable(const char* name, **kwargs):
+def Variable(name, **kwargs):
     """Create a symbolic variable with specified name.
 
     Parameters
@@ -241,6 +247,7 @@ def Variable(const char* name, **kwargs):
         The created variable symbol.
     """
     cdef SymbolHandle handle
+    name = c_str(name)
     CALL(NNSymbolCreateVariable(name, &handle))
     return NewSymbol(handle)
 
@@ -274,10 +281,10 @@ cdef _make_atomic_symbol_function(AtomicSymbolCreator handle):
     func_hint = func_name.lower()
 
     def creator(*args, **kwargs):
-        cdef vector[const char*] param_keys
-        cdef vector[const char*] param_vals
+        cdef vector[string] sparam_keys
+        cdef vector[string] sparam_vals
         cdef vector[SymbolHandle] symbol_args
-        cdef vector[const char*] symbol_keys
+        cdef vector[string] ssymbol_keys
         cdef SymbolHandle ret_handle
 
         name = kwargs.pop("name", None)
@@ -286,11 +293,11 @@ cdef _make_atomic_symbol_function(AtomicSymbolCreator handle):
         if len(kwargs) != 0:
             for k, v in kwargs.items():
                 if isinstance(v, Symbol):
-                    symbol_keys.push_back(k)
+                    ssymbol_keys.push_back(c_str(k))
                     symbol_args.push_back((<Symbol>v).handle)
                 else:
-                    param_keys.push_back(k)
-                    param_vals.push_back(str(v))
+                    sparam_keys.push_back(c_str(k))
+                    sparam_vals.push_back(c_str(str(v)))
 
         if len(args) != 0:
             if symbol_args.size() != 0:
@@ -301,6 +308,10 @@ cdef _make_atomic_symbol_function(AtomicSymbolCreator handle):
                     raise TypeError('Compose expect `Symbol` as arguments')
                 symbol_args.push_back((<Symbol>v).handle)
 
+        cdef vector[const char*] param_keys = SVec2Ptr(sparam_keys)
+        cdef vector[const char*] param_vals = SVec2Ptr(sparam_vals)
+        cdef vector[const char*] symbol_keys = SVec2Ptr(ssymbol_keys)
+
         CALL(NNSymbolCreateAtomicSymbol(
             handle,
             <nn_uint>param_keys.size(),
@@ -315,7 +326,9 @@ cdef _make_atomic_symbol_function(AtomicSymbolCreator handle):
         name = NameManager.current.get(name, func_hint)
 
         cdef const char* c_name = NULL
+
         if name:
+            name = c_str(name)
             c_name = name
 
         CALL(NNSymbolCompose(