Simplify the data backends. (#5893)

tests/python/test_basic.py

@@ -1,17 +1,14 @@
 # -*- coding: utf-8 -*-
 import sys
 from contextlib import contextmanager
-try:
-    # python 2
-    from StringIO import StringIO
-except ImportError:
-    # python 3
-    from io import StringIO
+from io import StringIO
 import numpy as np
+import os
 import xgboost as xgb
 import unittest
 import json
 from pathlib import Path
+import tempfile
 
 dpath = 'demo/data/'
 rng = np.random.RandomState(1994)
@@ -66,16 +63,19 @@ class TestBasic(unittest.TestCase):
         # error must be smaller than 10%
         assert err < 0.1
 
-        # save dmatrix into binary buffer
-        dtest.save_binary('dtest.buffer')
-        # save model
-        bst.save_model('xgb.model')
-        # load model and data in
-        bst2 = xgb.Booster(model_file='xgb.model')
-        dtest2 = xgb.DMatrix('dtest.buffer')
-        preds2 = bst2.predict(dtest2)
-        # assert they are the same
-        assert np.sum(np.abs(preds2 - preds)) == 0
+        with tempfile.TemporaryDirectory() as tmpdir:
+            dtest_path = os.path.join(tmpdir, 'dtest.dmatrix')
+            # save dmatrix into binary buffer
+            dtest.save_binary(dtest_path)
+            # save model
+            model_path = os.path.join(tmpdir, 'model.booster')
+            bst.save_model(model_path)
+            # load model and data in
+            bst2 = xgb.Booster(model_file=model_path)
+            dtest2 = xgb.DMatrix(dtest_path)
+            preds2 = bst2.predict(dtest2)
+            # assert they are the same
+            assert np.sum(np.abs(preds2 - preds)) == 0
 
     def test_record_results(self):
         dtrain = xgb.DMatrix(dpath + 'agaricus.txt.train')