change data format to include weight in binary file, add get weight to python

python/README.md

@@ -1,4 +1,3 @@
 python wrapper for xgboost using ctypes
 
 see example for usage
-

python/example/demo.py

@@ -2,7 +2,7 @@
 import sys
 import numpy as np
 import scipy.sparse
-# append the path to xgboost
+# append the path to xgboost, you may need to change the following line
 sys.path.append('../')
 import xgboost as xgb
 
@@ -82,7 +82,7 @@ evallist  = [(dtest,'eval'), (dtrain,'train')]
 bst = xgb.train( param, dtrain, num_round, evallist )
 
 ###
-# cutomsized loss function, set loss_type to 0, so that predict get untransformed score
+# advanced: cutomsized loss function, set loss_type to 0, so that predict get untransformed score
 # 
 print 'start running example to used cutomized objective function'
 

python/xgboost.py

@@ -19,6 +19,7 @@ xglib = ctypes.cdll.LoadLibrary(XGBOOST_PATH)
 xglib.XGDMatrixCreate.restype = ctypes.c_void_p
 xglib.XGDMatrixNumRow.restype = ctypes.c_ulong
 xglib.XGDMatrixGetLabel.restype =  ctypes.POINTER( ctypes.c_float )
+xglib.XGDMatrixGetWeight.restype =  ctypes.POINTER( ctypes.c_float )
 xglib.XGDMatrixGetRow.restype = ctypes.POINTER( REntry )
 xglib.XGBoosterPredict.restype = ctypes.POINTER( ctypes.c_float ) 
 
@@ -81,6 +82,11 @@ class DMatrix:
         length = ctypes.c_ulong()
         labels = xglib.XGDMatrixGetLabel(self.handle, ctypes.byref(length))
         return ctypes2numpy( labels, length.value );
+    # get weight from dmatrix
+    def get_weight(self):
+        length = ctypes.c_ulong()
+        weights = xglib.XGDMatrixGetWeight(self.handle, ctypes.byref(length))
+        return ctypes2numpy( weights, length.value );
     # clear everything
     def clear(self):
         xglib.XGDMatrixClear(self.handle)

python/xgboost_python.cpp

@@ -72,6 +72,10 @@ namespace xgboost{
                 *len = this->info.labels.size();
                 return &(this->info.labels[0]);
             }
+            inline const float* GetWeight( size_t* len ) const{
+                *len = this->info.weights.size();
+                return &(this->info.weights[0]);
+            }
             inline void CheckInit(void){
                 if(!init_col_){
                     this->data.InitData();
@@ -171,6 +175,9 @@ extern "C"{
     const float* XGDMatrixGetLabel( const void *handle, size_t* len ){
         return static_cast<const DMatrix*>(handle)->GetLabel(len);
     }
+    const float* XGDMatrixGetWeight( const void *handle, size_t* len ){
+        return static_cast<const DMatrix*>(handle)->GetWeight(len);
+    }
     void XGDMatrixClear(void *handle){
         static_cast<DMatrix*>(handle)->Clear();
     }