Default scope function

`Paddle` manages Scope as programming language's scope.  It just a
thread-local stack of Scope. Top of that stack is current scope, the
bottom of that stack is all scopes' parent.

Invoking `create_var/get_var`  can `create/get` variable in current
scope. Invoking `enter_local_scope/leave_local_scope` can create or
destroy local scope.

A `scoped_function` will take a `function` as input. That function will
be invoked in a new local scope.

python/paddle/v2/framework/default_scope_funcs.py

+"""
+Default scope function.
+
+`Paddle` manages Scope as programming language's scope.  It just a 
+thread-local stack of Scope. Top of that stack is current scope, the bottom 
+of that stack is all scopes' parent. 
+
+Invoking `create_var/get_var`  can `create/get` variable in current scope. 
+Invoking `enter_local_scope/leave_local_scope` can create or destroy local 
+scope. 
+
+A `scoped_function` will take a `function` as input. That function will be 
+invoked in a new local scope. 
+"""
+
+import paddle.v2.framework.core
+import threading
+
+__tl_scope__ = threading.local()
+
+__all__ = [
+    'get_cur_scope', 'enter_local_scope', 'leave_local_scope', 'create_var',
+    'get_var', 'scoped_function'
+]
+
+
+def get_cur_scope():
+    """
+    Get current scope.
+    :rtype: paddle.v2.framework.core.Scope
+    """
+    cur_scope_stack = getattr(__tl_scope__, 'cur_scope', None)
+    if cur_scope_stack is None:
+        __tl_scope__.cur_scope = list()
+    if len(__tl_scope__.cur_scope) == 0:
+        __tl_scope__.cur_scope.append(paddle.v2.framework.core.Scope(None))
+    return __tl_scope__.cur_scope[-1]
+
+
+def enter_local_scope():
+    """
+    Enter a new local scope
+    """
+    cur_scope = get_cur_scope()
+    new_scope = paddle.v2.framework.core.Scope(cur_scope)
+    __tl_scope__.cur_scope.append(new_scope)
+
+
+def leave_local_scope():
+    """
+    Leave local scope
+    """
+    __tl_scope__.cur_scope.pop()
+
+
+def create_var(name):
+    """
+    create variable in current scope.
+    """
+    return get_cur_scope().create_var(name)
+
+
+def get_var(name):
+    """
+    get variable in current scope.
+    """
+    return get_cur_scope().get_var(name)
+
+
+def scoped_function(func):
+    """
+    invoke `func` in new scope.
+    
+    :param func: a callable function that will be run in new scope.
+    :type func: callable
+    """
+    enter_local_scope()
+    try:
+        func()
+    except:
+        raise
+    finally:
+        leave_local_scope()

python/paddle/v2/framework/tests/CMakeLists.txt

-add_python_test(test_framework test_protobuf.py test_scope.py)
+add_python_test(test_framework test_protobuf.py test_scope.py
+    test_default_scope_funcs.py)

python/paddle/v2/framework/tests/test_default_scope_funcs.py

+from paddle.v2.framework.default_scope_funcs import *
+import unittest
+
+
+class TestDefaultScopeFuncs(unittest.TestCase):
+    def test_cur_scope(self):
+        self.assertIsNotNone(get_cur_scope())
+
+    def test_none_variable(self):
+        self.assertIsNone(get_var("test"))
+
+    def test_create_var_get_var(self):
+        var_a = create_var("var_a")
+        self.assertIsNotNone(var_a)
+        self.assertIsNotNone(get_cur_scope().get_var('var_a'))
+        enter_local_scope()
+        self.assertIsNotNone(get_cur_scope().get_var('var_a'))
+        leave_local_scope()
+
+    def test_var_get_int(self):
+        def __new_scope__():
+            i = create_var("var_i")
+            self.assertFalse(i.is_int())
+            i.set_int(10)
+            self.assertTrue(i.is_int())
+            self.assertEqual(10, i.get_int())
+
+        for _ in xrange(10):
+            scoped_function(__new_scope__)
+
+
+if __name__ == '__main__':
+    unittest.main()