Refine en doc (#20317)

* test=develop, fix docker with paddle nccl problem

* test=develop, refine en_doc for Variable and Program

* test=document_fix, fix English doc for Variable and Program

* test=document_fix, refine astype code block style

* test=document_fix, add example code for Variable properties

paddle/fluid/API.spec

-paddle.fluid.Program ('paddle.fluid.framework.Program', ('document', '4f9e1829c89e0711355820e935d2b447'))
+paddle.fluid.Program ('paddle.fluid.framework.Program', ('document', '9d8de4f0398ff2b01d4b572ee412b6aa'))
 paddle.fluid.Program.__init__ (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
-paddle.fluid.Program.block (ArgSpec(args=['self', 'index'], varargs=None, keywords=None, defaults=None), ('document', '28d066e432ceda86810b1e7deb8a4afa'))
-paddle.fluid.Program.clone (ArgSpec(args=['self', 'for_test'], varargs=None, keywords=None, defaults=(False,)), ('document', '1e910e8c4186e8ff1afb62602f369033'))
-paddle.fluid.Program.current_block (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '365e49ce9f346ac6d54265e29db447b5'))
-paddle.fluid.Program.global_block (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', 'dd3f2b49147861d6ae48989a77482f05'))
-paddle.fluid.Program.list_vars (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '757cf8d083dff9507676b17376ac5af1'))
-paddle.fluid.Program.parse_from_string (ArgSpec(args=['binary_str'], varargs=None, keywords=None, defaults=None), ('document', '70e063a0a09d5a8ed322db0d5de9edb4'))
-paddle.fluid.Program.to_string (ArgSpec(args=['self', 'throw_on_error', 'with_details'], varargs=None, keywords=None, defaults=(False,)), ('document', '6dfb00cd50eb515dcf2548a68ea94bfb'))
-paddle.fluid.default_startup_program (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', 'accb52b28228f8e93a26fabdc960f56c'))
+paddle.fluid.Program.block (ArgSpec(args=['self', 'index'], varargs=None, keywords=None, defaults=None), ('document', 'f2b2f468fef697ede6ea5bf7a9ba489c'))
+paddle.fluid.Program.clone (ArgSpec(args=['self', 'for_test'], varargs=None, keywords=None, defaults=(False,)), ('document', 'c60aaaa8e2ca192dadffbb6ef0de8f60'))
+paddle.fluid.Program.current_block (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '0efa58429d84407256665cc1ad66a240'))
+paddle.fluid.Program.global_block (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '0a25153e749268585354f8ae7eb2713b'))
+paddle.fluid.Program.list_vars (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '81440aaee8e4cb6c3488e8f9bbf1143e'))
+paddle.fluid.Program.parse_from_string (ArgSpec(args=['binary_str'], varargs=None, keywords=None, defaults=None), ('document', 'fc4a5660ff4280278402688f0014ce7f'))
+paddle.fluid.Program.to_string (ArgSpec(args=['self', 'throw_on_error', 'with_details'], varargs=None, keywords=None, defaults=(False,)), ('document', '7dde33f16b63aa50d474870a9cebb539'))
+paddle.fluid.default_startup_program (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', 'f53890b2fb8c0642b6047e4fee2d6d58'))
 paddle.fluid.default_main_program (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', '853718df675e59aea7104f3d61bbf11d'))
 paddle.fluid.program_guard (ArgSpec(args=['main_program', 'startup_program'], varargs=None, keywords=None, defaults=(None,)), ('document', '78fb5c7f70ef76bcf4a1862c3f6b8191'))
 paddle.fluid.name_scope (ArgSpec(args=['prefix'], varargs=None, keywords=None, defaults=(None,)), ('document', '917d313881ff990de5fb18d98a9c7b42'))
@@ -16,16 +16,16 @@ paddle.fluid.cpu_places (ArgSpec(args=['device_count'], varargs=None, keywords=N
 paddle.fluid.cuda_pinned_places (ArgSpec(args=['device_count'], varargs=None, keywords=None, defaults=(None,)), ('document', '567ac29567716fd8e7432b533337d529'))
 paddle.fluid.in_dygraph_mode (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', 'df1f4d1ed7e1eefe04f6361efda6b75a'))
 paddle.fluid.is_compiled_with_cuda (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', '60c7f107a5050aeb58bb74eb175672b5'))
-paddle.fluid.Variable ('paddle.fluid.framework.Variable', ('document', '65ff735c2b96673d7131f5ff6b0db40c'))
+paddle.fluid.Variable ('paddle.fluid.framework.Variable', ('document', '8e51f2adcad7ae33aa35a178cceebdf6'))
 paddle.fluid.Variable.__init__ (ArgSpec(args=['self', 'block', 'type', 'name', 'shape', 'dtype', 'lod_level', 'capacity', 'persistable', 'error_clip', 'stop_gradient', 'is_data', 'need_check_feed'], varargs=None, keywords='kwargs', defaults=(VarType.LOD_TENSOR, None, None, None, None, None, None, None, False, False, False)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
-paddle.fluid.Variable.astype (ArgSpec(args=['self', 'dtype'], varargs=None, keywords=None, defaults=None), ('document', '78541af4039262ed7ce3c447f8cc9cc1'))
-paddle.fluid.Variable.backward (ArgSpec(args=['self', 'backward_strategy'], varargs=None, keywords=None, defaults=(None,)), ('document', 'cb928fa194da09694f4267f0a25268f1'))
-paddle.fluid.Variable.clear_gradient (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '509a96d23c876fc5bfb10e1147e21d5f'))
-paddle.fluid.Variable.detach (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '0730b2d310b014d9b0a903b2034757d7'))
-paddle.fluid.Variable.gradient (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '86b246bfaf20f3058e91927abbcf9fb9'))
-paddle.fluid.Variable.numpy (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '7536e8feb56d827875943e7f01d406fc'))
-paddle.fluid.Variable.set_value (ArgSpec(args=['self', 'value'], varargs=None, keywords=None, defaults=None), ('document', 'c424b9e763ff51c38a6917f98026fe7d'))
-paddle.fluid.Variable.to_string (ArgSpec(args=['self', 'throw_on_error', 'with_details'], varargs=None, keywords=None, defaults=(False,)), ('document', '31f359a2c074f26dc0ffff296fc3983f'))
+paddle.fluid.Variable.astype (ArgSpec(args=['self', 'dtype'], varargs=None, keywords=None, defaults=None), ('document', 'ffc7049afe250829b56986c40cf3cca3'))
+paddle.fluid.Variable.backward (ArgSpec(args=['self', 'backward_strategy'], varargs=None, keywords=None, defaults=(None,)), ('document', 'a2fabca0102442aae4d6537028574d07'))
+paddle.fluid.Variable.clear_gradient (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', 'c6e511dcccf51a95eeb83447322b4345'))
+paddle.fluid.Variable.detach (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '833afb90a8d9353610e3d671b2de9f4f'))
+paddle.fluid.Variable.gradient (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', 'b8fe1354051f3cc953c280c8cabdd3fc'))
+paddle.fluid.Variable.numpy (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '760ab11e4019258b3004fe9002819170'))
+paddle.fluid.Variable.set_value (ArgSpec(args=['self', 'value'], varargs=None, keywords=None, defaults=None), ('document', '69deb77a9dedc61f7b731a6a7709fa5b'))
+paddle.fluid.Variable.to_string (ArgSpec(args=['self', 'throw_on_error', 'with_details'], varargs=None, keywords=None, defaults=(False,)), ('document', '65cd237e2d30c12e412c9cafbbd00791'))
 paddle.fluid.load_op_library (ArgSpec(args=['lib_filename'], varargs=None, keywords=None, defaults=None), ('document', 'c009b2ea5fb6520f2d2f53aafec788e0'))
 paddle.fluid.Executor ('paddle.fluid.executor.Executor', ('document', 'dcb7d6de26088df84b74226bf24f4ae1'))
 paddle.fluid.Executor.__init__ (ArgSpec(args=['self', 'place'], varargs=None, keywords=None, defaults=None), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))

python/paddle/fluid/layers/math_op_patch.py

@@ -93,14 +93,48 @@ def monkey_patch_variable():
 
     def astype(self, dtype):
         """
+        **Notes**:
+            **The variable must be a** :ref:`api_fluid_Tensor`
+
         Cast a variable to a specified data type.
-        NOTE: The variable must be a Tensor
+
         Args:
+
             self(Variable): The source variable
-            dtype: The target dtype
+
+            dtype: The target data type
 
         Returns:
-            Variable with new dtype
+            Variable: Variable with new dtype
+
+        Examples:
+            In Static Graph Mode:
+
+            .. code-block:: python
+
+                import paddle.fluid as fluid
+
+                startup_prog = fluid.Program()
+                main_prog = fluid.Program()
+                with fluid.program_guard(startup_prog, main_prog):
+                    original_variable = fluid.data(name = "new_variable", shape=[2,2], dtype='float32')
+                    new_variable = original_variable.astype('int64')
+                    print("new var's dtype is: {}".format(new_variable.dtype))
+
+            In Dygraph Mode:
+
+            .. code-block:: python
+
+                import paddle.fluid as fluid
+                import numpy as np
+
+                x = np.ones([2, 2], np.float32)
+                with fluid.dygraph.guard():
+                    original_variable = fluid.dygraph.to_variable(x)
+                    print("original var's dtype is: {}, numpy dtype is {}".format(original_variable.dtype, original_variable.numpy().dtype))
+                    new_variable = original_variable.astype('int64')
+                    print("new var's dtype is: {}, numpy dtype is {}".format(new_variable.dtype, new_variable.numpy().dtype))
+
         """
         block = current_block(self)
         out = create_new_tmp_var(block, dtype)