Always remove what we add from sys.path.

theano/gof/lazylinker_c.py

@@ -7,21 +7,26 @@ from theano.gof import cmodule
 
 _logger = logging.getLogger('theano.gof.lazylinker_c')
 
-# Ensure the compiledir is in `sys.path` to be able to reload an existing
-# precompiled library.
-if config.compiledir not in sys.path:
-    sys.path.append(config.compiledir)
-
 force_compile = False
 version = 0.20  # must match constant returned in function get_version()
 
+def try_import():
+    global lazylinker_ext
+    sys.path[0:0] = [config.compiledir]
+    import lazylinker_ext
+    del sys.path[0]
+
+def try_reload():
+    sys.path[0:0] = [config.compiledir]
+    reload(lazylinker_ext)
+    del sys.path[0]
 
 try:
     _need_reload = False
     if force_compile:
         raise ImportError()
     else:
-        import lazylinker_ext
+        try_import()
         _need_reload = True
         if version != getattr(lazylinker_ext, '_version', None):
             raise ImportError()
@@ -36,9 +41,9 @@ except ImportError:
             if _need_reload:
                 # The module was successfully imported earlier: we need to
                 # reload it to check if the version was updated.
-                reload(lazylinker_ext)
+                try_reload()
             else:
-                import lazylinker_ext
+                try_import()
                 _need_reload = True
             if version != getattr(lazylinker_ext, '_version', None):
                 raise ImportError()
@@ -65,8 +70,8 @@ except ImportError:
             init_pyc = os.path.join(loc, '__init__.pyc')
             if os.path.isfile(init_pyc):
                 os.remove(init_pyc)
-            import lazylinker_ext
-            reload(lazylinker_ext)
+            try_import()
+            try_reload()
             from lazylinker_ext import lazylinker_ext as lazy_c
             assert (lazylinker_ext._version ==
                     lazy_c.get_version())

theano/sandbox/cuda/__init__.py

@@ -107,9 +107,9 @@ def try_import():
     try:
         # If we load a previously-compiled version, config.compiledir should
         # be in sys.path.
-        if config.compiledir not in sys.path:
-            sys.path.append(config.compiledir)
+        sys.path[0:0] = [config.compiledir]
         import cuda_ndarray.cuda_ndarray
+        del sys.path[0]
     except ImportError:
         return False
     return True

theano/scan_module/scan_perform_ext.py

@@ -12,16 +12,24 @@ _logger = logging.getLogger('theano.scan_module.scan_perform')
 _logger.setLevel(logging.WARN)
 
 
-# Ensure the compiledir is in `sys.path` to be able to reload an existing
-# precompiled library.
-if config.compiledir not in sys.path:
-    sys.path.append(config.compiledir)
-
 version = 0.278  # must match constant returned in function get_version()
 
 need_reload = False
-try:
+
+
+def try_import():
+    sys.path[0:0] = [config.compiledir]
     import scan_perform
+    del sys.path[0]
+
+
+def try_reload()
+    sys.path[0:0] = [config.compiledir]
+    reload(scan_perform)
+    del sys.path[0]
+
+try:
+    try_import()
     need_reload = True
     if version != getattr(scan_perform, '_version', None):
         raise ImportError()
@@ -34,9 +42,9 @@ except ImportError:
             if need_reload:
                 # The module was successfully imported earlier: we need to
                 # reload it to check if the version was updated.
-                reload(scan_perform)
+                try_reload()
             else:
-                import scan_perform
+                try_import()
                 need_reload = True
             if version != getattr(scan_perform, '_version', None):
                 raise ImportError()
@@ -66,8 +74,9 @@ except ImportError:
             init_pyc = os.path.join(loc, '__init__.pyc')
             if os.path.isfile(init_pyc):
                 os.remove(init_pyc)
-            import scan_perform
-            reload(scan_perform)
+            try_import()
+
+            try_reload()
             from scan_perform import scan_perform as scan_c
             assert (scan_perform._version ==
                     scan_c.get_version())