diff --git a/fastNLP/__init__.py b/fastNLP/__init__.py
index 6007ed07..b856faff 100644
--- a/fastNLP/__init__.py
+++ b/fastNLP/__init__.py
@@ -1,10 +1,3 @@
 
-# 首先保证 FASTNLP_GLOBAL_RANK 正确设置
-from fastNLP.envs.set_env_on_import import set_env_on_import
-set_env_on_import()
-
-# 再设置 backend 相关
-from fastNLP.envs.set_backend import _set_backend
-_set_backend()
-
+from fastNLP.envs import *
 from fastNLP.core import Trainer, Evaluator
\ No newline at end of file
diff --git a/fastNLP/core/collators/padders/get_padder.py b/fastNLP/core/collators/padders/get_padder.py
index 051a0ffc..ecef9fcf 100644
--- a/fastNLP/core/collators/padders/get_padder.py
+++ b/fastNLP/core/collators/padders/get_padder.py
@@ -84,25 +84,25 @@ def get_padder(batch_field:Sequence[Any], pad_val, dtype, backend, field_name)->
     try:
         if depth == 1 and shape_len == 0:  # 形如 [0, 1, 2] 或 [True, False, True]
             if backend == 'raw':
-                return RawNumberPadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return RawNumberPadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
             elif backend == 'numpy':
-                return NumpyNumberPadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return NumpyNumberPadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
             elif backend == 'torch':
-                return TorchNumberPadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return TorchNumberPadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
 
         if depth > 1 and shape_len == 0:  # 形如 [[0, 1], [2]] 这种
             if backend == 'raw':
-                return RawSequencePadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return RawSequencePadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
             elif backend == 'numpy':
-                return NumpySequencePadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return NumpySequencePadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
             elif backend == 'torch':
-                return TorchSequencePadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return TorchSequencePadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
 
         if depth == 1 and shape_len != 0:
             if backend == 'numpy':
-                return NumpyTensorPadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return NumpyTensorPadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
             elif backend == 'torch':
-                return TorchTensorPadder(ele_dtype=ele_dtype, pad_val=pad_val, dtype=dtype)
+                return TorchTensorPadder(pad_val=pad_val, ele_dtype=ele_dtype, dtype=dtype)
 
         if shape_len != 0 and depth>1:
             msg = "Does not support pad tensor under nested list. If you need this, please report."
diff --git a/fastNLP/core/collators/padders/numpy_padder.py b/fastNLP/core/collators/padders/numpy_padder.py
index 0298fd86..40b70683 100644
--- a/fastNLP/core/collators/padders/numpy_padder.py
+++ b/fastNLP/core/collators/padders/numpy_padder.py
@@ -1,6 +1,7 @@
 __all__ = [
     'NumpyNumberPadder',
     'NumpySequencePadder',
+    "NumpyTensorPadder"
 ]
 
 from numbers import Number
@@ -14,7 +15,7 @@ from .exceptions import *
 
 
 def _get_dtype(ele_dtype, dtype, class_name):
-    if not is_number_or_numpy_number(ele_dtype):
+    if ele_dtype is not None and not is_number_or_numpy_number(ele_dtype):
         raise EleDtypeUnsupportedError(f"`{class_name}` only supports padding python numbers "
                                        f"or numpy numbers but get `{ele_dtype}`.")
 
@@ -29,7 +30,14 @@ def _get_dtype(ele_dtype, dtype, class_name):
 
 
 class NumpyNumberPadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
+        """
+        可以将形如 [1, 2, 3] 这类的数据转为 np.array([1, 2, 3])
+
+        :param pad_val: 该值无意义
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 np.array 类型。
+        :param dtype: 输出的数据的 dtype 是什么
+        """
         dtype = _get_dtype(ele_dtype, dtype, self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
 
@@ -39,7 +47,14 @@ class NumpyNumberPadder(Padder):
 
 
 class NumpySequencePadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
+        """
+        将类似于 [[1], [1, 2]] 的内容 pad 为 np.array([[1, 0], [1, 2]]) 可以 pad 多重嵌套的数据。
+
+        :param pad_val: pad 的值是多少。
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 np.array 类型。
+        :param dtype: 输出的数据的 dtype 是什么
+        """
         dtype = _get_dtype(ele_dtype, dtype, self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
 
@@ -49,13 +64,13 @@ class NumpySequencePadder(Padder):
 
 
 class NumpyTensorPadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
         """
         pad 类似于 [np.array([3, 4], np.array([1])] 的 field
 
-        :param ele_dtype:
-        :param pad_val:
-        :param dtype:
+        :param pad_val: pad 的值是多少。
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 np.array 类型。
+        :param dtype: 输出的数据的 dtype 是什么
         """
         dtype = _get_dtype(ele_dtype, dtype, self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
diff --git a/fastNLP/core/collators/padders/padder.py b/fastNLP/core/collators/padders/padder.py
index 486574af..065ce39f 100644
--- a/fastNLP/core/collators/padders/padder.py
+++ b/fastNLP/core/collators/padders/padder.py
@@ -14,6 +14,13 @@ class Padder:
 
 class NullPadder(Padder):
     def __init__(self, ele_dtype=None, pad_val=None, dtype=None):
+        """
+        不进行任何 检查 与 pad 的空 padder 。
+
+        :param ele_dtype:
+        :param pad_val:
+        :param dtype:
+        """
         super().__init__(pad_val=pad_val, dtype=dtype)
 
     def __call__(self, batch_field):
diff --git a/fastNLP/core/collators/padders/raw_padder.py b/fastNLP/core/collators/padders/raw_padder.py
index 66393b40..fe0c0b14 100644
--- a/fastNLP/core/collators/padders/raw_padder.py
+++ b/fastNLP/core/collators/padders/raw_padder.py
@@ -1,25 +1,35 @@
 
 
 from .padder import Padder
-from .utils import get_padded_nest_list, is_number, get_padded_numpy_array
+from .utils import is_number, get_padded_numpy_array, is_number_or_numpy_number
 from .exceptions import *
 
 
 def _get_dtype(ele_dtype, dtype, class_name):
-    if is_number(ele_dtype):
-        if dtype is None:
-            dtype = ele_dtype
-        elif not is_number(dtype):
-            raise DtypeUnsupportedError(f"The dtype of `{class_name}` can only be None but "
-                                        f"get `{dtype}`.")
-    else:
+    if ele_dtype is not None and not is_number_or_numpy_number(ele_dtype):
         raise EleDtypeUnsupportedError(f"`{class_name}` only supports padding python numbers "
-                                       f"but get `{ele_dtype}`.")
+                                       f"or numpy numbers but get `{ele_dtype}`.")
+
+    if dtype is None:
+        dtype = ele_dtype
+    else:
+        if not is_number_or_numpy_number(dtype):
+            raise DtypeUnsupportedError(f"The dtype of `{class_name}` only supports python numbers "
+                                        f"or numpy numbers but get `{dtype}`.")
+        dtype = dtype
+
     return dtype
 
 
 class RawNumberPadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
+        """
+        可以将形如 [1, 2, 3] 这类的数据转为 [1, 2, 3] 。实际上该 padder 无意义。
+
+        :param pad_val: 该值无意义
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 np.array 类型。
+        :param dtype: 输出的数据的 dtype 是什么
+        """
         dtype = _get_dtype(ele_dtype, dtype, self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
 
@@ -32,7 +42,14 @@ class RawNumberPadder(Padder):
 
 
 class RawSequencePadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
+        """
+        将类似于 [[1], [1, 2]] 的内容 pad 为 [[1, 0], [1, 2]] 。可以 pad 多重嵌套的数据。
+
+        :param pad_val: pad 的值
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 np.array 类型。
+        :param dtype: 输出的数据的 dtype 是什么
+        """
         dtype = _get_dtype(ele_dtype, dtype, self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
 
diff --git a/fastNLP/core/collators/padders/torch_padder.py b/fastNLP/core/collators/padders/torch_padder.py
index a6768435..7c0eaa33 100644
--- a/fastNLP/core/collators/padders/torch_padder.py
+++ b/fastNLP/core/collators/padders/torch_padder.py
@@ -37,7 +37,7 @@ def is_torch_tensor(dtype):
 
 
 def _get_dtype(ele_dtype, dtype, class_name):
-    if not (is_number_or_numpy_number(ele_dtype) or is_torch_tensor(ele_dtype)):
+    if not (ele_dtype is not None and (is_number_or_numpy_number(ele_dtype) or is_torch_tensor(ele_dtype))):
         raise EleDtypeUnsupportedError(f"`{class_name}` only supports padding python numbers "
                                        f"or numpy numbers or torch.Tensor but get `{ele_dtype}`.")
 
@@ -47,20 +47,27 @@ def _get_dtype(ele_dtype, dtype, class_name):
                                         f"or torch.dtype but get `{dtype}`.")
         dtype = number_to_torch_dtype_dict.get(dtype, dtype)
     else:
-        if (is_number(ele_dtype) or is_torch_tensor(ele_dtype)):
-            ele_dtype = number_to_torch_dtype_dict.get(ele_dtype, ele_dtype)
-            dtype = ele_dtype
-        elif is_numpy_number_dtype(ele_dtype): # 存在一个转换的问题了
-            dtype = numpy_to_torch_dtype_dict.get(ele_dtype.type)
-        elif is_numpy_generic_class(ele_dtype):
-            dtype = numpy_to_torch_dtype_dict.get(ele_dtype)
+        if ele_dtype is not None:
+            if (is_number(ele_dtype) or is_torch_tensor(ele_dtype)):
+                ele_dtype = number_to_torch_dtype_dict.get(ele_dtype, ele_dtype)
+                dtype = ele_dtype
+            elif is_numpy_number_dtype(ele_dtype): # 存在一个转换的问题了
+                dtype = numpy_to_torch_dtype_dict.get(ele_dtype.type)
+            elif is_numpy_generic_class(ele_dtype):
+                dtype = numpy_to_torch_dtype_dict.get(ele_dtype)
 
     return dtype
 
 
 class TorchNumberPadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
-        # 仅当 ele_dtype 是 python number/ numpy number 或者 tensor
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
+        """
+        可以将形如 [1, 2, 3] 这类的数据转为 torch.Tensor([1, 2, 3])
+
+        :param pad_val: 该值无意义
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 torch.tensor 类型。
+        :param dtype: 输出的数据的 dtype 是什么。如 torch.long, torch.float32, int, float 等
+        """
         dtype = _get_dtype(ele_dtype, dtype, class_name=self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
 
@@ -70,7 +77,14 @@ class TorchNumberPadder(Padder):
 
 
 class TorchSequencePadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
+        """
+        将类似于 [[1], [1, 2]] 的内容 pad 为 torch.Tensor([[1, 0], [1, 2]]) 可以 pad 多重嵌套的数据。
+
+        :param pad_val: 需要 pad 的值。
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 torch.tensor 类型。
+        :param dtype: 输出的数据的 dtype 是什么。如 torch.long, torch.float32, int, float 等
+        """
         dtype = _get_dtype(ele_dtype, dtype, class_name=self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
 
@@ -81,13 +95,13 @@ class TorchSequencePadder(Padder):
 
 
 class TorchTensorPadder(Padder):
-    def __init__(self, ele_dtype, pad_val=0, dtype=None):
+    def __init__(self, pad_val=0, ele_dtype=None, dtype=None):
         """
         目前仅支持 [torch.tensor([3, 2], torch.tensor([1])] 类似的
 
-        :param ele_dtype:
-        :param pad_val:
-        :param dtype:
+        :param pad_val: 需要 pad 的值。
+        :param ele_dtype: 用于检测当前 field 的元素类型是否可以转换为 torch.tensor 类型。
+        :param dtype: 输出的数据的 dtype 是什么。如 torch.long, torch.float32, int, float 等
         """
         dtype = _get_dtype(ele_dtype, dtype, class_name=self.__class__.__name__)
         super().__init__(pad_val=pad_val, dtype=dtype)
@@ -96,8 +110,6 @@ class TorchTensorPadder(Padder):
     def pad(batch_field, pad_val, dtype):
         shapes = [field.shape for field in batch_field]
         max_shape = [len(batch_field)] + [max(*_) for _ in zip(*shapes)]
-        if isinstance(dtype, np.dtype):
-            print(dtype)
         tensor = torch.full(max_shape, fill_value=pad_val, dtype=dtype)
         for i, field in enumerate(batch_field):
             slices = (i, ) + tuple(slice(0, s) for s in shapes[i])
diff --git a/fastNLP/core/collators/padders/torch_utils.py b/fastNLP/core/collators/padders/torch_utils.py
index a47bea0e..3f21333b 100644
--- a/fastNLP/core/collators/padders/torch_utils.py
+++ b/fastNLP/core/collators/padders/torch_utils.py
@@ -10,8 +10,7 @@ def is_torch_tensor_dtype(dtype) -> bool:
     """
     返回当前 dtype 是否是 torch 的 dtype 类型
 
-
-    :param dtype: 应该是通过类似与 torch.ones(3).dtype 方式获得结果
+    :param dtype: 类似与 torch.ones(3).dtype
     :return:
     """
     try:
diff --git a/fastNLP/core/dataloaders/torch_dataloader/fdl.py b/fastNLP/core/dataloaders/torch_dataloader/fdl.py
index 02721aaf..a21a7e9d 100644
--- a/fastNLP/core/dataloaders/torch_dataloader/fdl.py
+++ b/fastNLP/core/dataloaders/torch_dataloader/fdl.py
@@ -64,7 +64,7 @@ class TorchDataLoader(DataLoader):
         :param sampler: sampler实例化对象
         :param batch_sampler: batch_sampler实例化对象，其能迭代返回一个list的index数据
         :param num_workers: 进程的数量，当num_worker=0时不开启多进程
-        :param collate_fn: 对取得到的数据进行打包的callable函数
+        :param collate_fn: 对取得到的数据进行打包的callable函数。[None, auto, callable]
         :param pin_memory:
         :param drop_last: 是否去掉最后一个不符合batch_size的数据
         :param timeout:
@@ -178,6 +178,16 @@ class TorchDataLoader(DataLoader):
         """
         return self.cur_batch_indices
 
+    def set_pad(self):
+        pass
+
+    def set_ignore(self):
+        pass
+
+    def set_backend(self):
+        pass
+
+
 
 def prepare_torch_dataloader(ds_or_db: Union[DataSet, DataBundle, Sequence[DataSet], Mapping[str, DataSet]],
                              batch_size: int = 1,
diff --git a/fastNLP/core/dataset/dataset.py b/fastNLP/core/dataset/dataset.py
index cd887253..a2e0ddae 100644
--- a/fastNLP/core/dataset/dataset.py
+++ b/fastNLP/core/dataset/dataset.py
@@ -760,8 +760,7 @@ class DataSet:
         dict_ = {key: value.content for key, value in self.field_arrays.items()}
         return pd.DataFrame.from_dict(dict_)
 
-    # TODO 应该有返回值的吧
-    def to_csv(self, path: str) -> None:
+    def to_csv(self, path: str):
         """
         将dataset保存为csv文件
 
@@ -770,7 +769,7 @@ class DataSet:
         """
 
         df = self.to_pandas()
-        df.to_csv(path, encoding="utf-8")
+        return df.to_csv(path, encoding="utf-8")
 
     def add_collate_fn(self, collate_fn: Callable) -> None:
         """
@@ -831,4 +830,8 @@ class DataSet:
         """
         self.collate_fns.set_input(*field_names)
 
-
+    @property
+    def collator(self):
+        if self._collator is None:
+            self._collator = Collator()
+        return self._collator
diff --git a/fastNLP/envs/__init__.py b/fastNLP/envs/__init__.py
index 8ec8f3a4..bc09c33b 100644
--- a/fastNLP/envs/__init__.py
+++ b/fastNLP/envs/__init__.py
@@ -14,7 +14,11 @@ __all__ = [
 
 from .env import *
 from .set_env_on_import import set_env_on_import
-from .set_backend import dump_fastnlp_backend
+# 首先保证 FASTNLP_GLOBAL_RANK 正确设置
+set_env_on_import()
+from .set_backend import dump_fastnlp_backend, _set_backend
+# 再设置 backend 相关
+_set_backend()
 from .imports import *
 from .utils import _module_available, get_gpu_count
 from .distributed import *
diff --git a/fastNLP/envs/imports.py b/fastNLP/envs/imports.py
index 3d49afe4..a2b63953 100644
--- a/fastNLP/envs/imports.py
+++ b/fastNLP/envs/imports.py
@@ -5,9 +5,9 @@ import operator
 
 from fastNLP.envs.env import FASTNLP_BACKEND
 from fastNLP.envs.utils import _module_available, _compare_version
+from fastNLP.envs.set_backend import SUPPORT_BACKENDS
 
 
-SUPPORT_BACKENDS = ['torch', 'paddle', 'jittor']
 backend = os.environ.get(FASTNLP_BACKEND, 'all')
 if backend == 'all':
     need_import = SUPPORT_BACKENDS
diff --git a/fastNLP/envs/set_backend.py b/fastNLP/envs/set_backend.py
index 4d6fb915..553dd389 100644
--- a/fastNLP/envs/set_backend.py
+++ b/fastNLP/envs/set_backend.py
@@ -1,7 +1,3 @@
-"""
-这个文件用于自动以及手动设置某些环境变量的，该文件中的set_env()函数会在 fastNLP 被 import 的时候在set_env_on_import之后运行。可以
-    用于设置某些必要的环境变量。同时用户在使用时set_env()修改环境变量时，也应该保证set_env()函数在所有其它代码之前被运行。
-"""
 import os
 import json
 import sys
@@ -9,9 +5,12 @@ from collections import defaultdict
 
 
 from fastNLP.envs.env import FASTNLP_BACKEND, FASTNLP_GLOBAL_RANK, USER_CUDA_VISIBLE_DEVICES, FASTNLP_GLOBAL_SEED
-from fastNLP.envs.imports import SUPPORT_BACKENDS
 from fastNLP.envs.utils import _module_available, get_gpu_count
 
+
+SUPPORT_BACKENDS = ['torch', 'paddle', 'jittor']
+
+
 def _set_backend():
     """
     根据环境变量或者默认配置文件设置 backend 。
diff --git a/fastNLP/io/cws.py b/fastNLP/io/cws.py
deleted file mode 100644
index d88d6a00..00000000
--- a/fastNLP/io/cws.py
+++ /dev/null
@@ -1,97 +0,0 @@
-r"""undocumented"""
-
-__all__ = [
-    "CWSLoader"
-]
-
-import glob
-import os
-import random
-import shutil
-import time
-
-from .loader import Loader
-from fastNLP.core.dataset import DataSet, Instance
-
-
-class CWSLoader(Loader):
-    r"""
-    CWSLoader支持的数据格式为，一行一句话，不同词之间用空格隔开, 例如：
-
-    Example::
-
-        上海 浦东 开发 与 法制 建设 同步
-        新华社 上海 二月 十日 电 （ 记者 谢金虎 、 张持坚 ）
-        ...
-
-    该Loader读取后的DataSet具有如下的结构
-
-    .. csv-table::
-       :header: "raw_words"
-
-       "上海 浦东 开发 与 法制 建设 同步"
-       "新华社 上海 二月 十日 电 （ 记者 谢金虎 、 张持坚 ）"
-       "..."
-       
-    """
-
-    def __init__(self, dataset_name: str = None):
-        r"""
-        
-        :param str dataset_name: data的名称，支持pku, msra, cityu(繁体), as(繁体), None
-        """
-        super().__init__()
-        datanames = {'pku': 'cws-pku', 'msra': 'cws-msra', 'as': 'cws-as', 'cityu': 'cws-cityu'}
-        if dataset_name in datanames:
-            self.dataset_name = datanames[dataset_name]
-        else:
-            self.dataset_name = None
-
-    def _load(self, path: str):
-        ds = DataSet()
-        with open(path, 'r', encoding='utf-8') as f:
-            for line in f:
-                line = line.strip()
-                if line:
-                    ds.append(Instance(raw_words=line))
-        return ds
-
-    def download(self, dev_ratio=0.1, re_download=False) -> str:
-        r"""
-        如果你使用了该数据集，请引用以下的文章:Thomas Emerson, The Second International Chinese Word Segmentation Bakeoff,
-        2005. 更多信息可以在http://sighan.cs.uchicago.edu/bakeoff2005/查看
-
-        :param float dev_ratio: 如果路径中没有dev集，从train划分多少作为dev的数据. 如果为0，则不划分dev。
-        :param bool re_download: 是否重新下载数据，以重新切分数据。
-        :return: str
-        """
-        if self.dataset_name is None:
-            return ''
-        data_dir = self._get_dataset_path(dataset_name=self.dataset_name)
-        modify_time = 0
-        for filepath in glob.glob(os.path.join(data_dir, '*')):
-            modify_time = os.stat(filepath).st_mtime
-            break
-        if time.time() - modify_time > 1 and re_download:  # 通过这种比较丑陋的方式判断一下文件是否是才下载的
-            shutil.rmtree(data_dir)
-            data_dir = self._get_dataset_path(dataset_name=self.dataset_name)
-
-        if not os.path.exists(os.path.join(data_dir, 'dev.txt')):
-            if dev_ratio > 0:
-                assert 0 < dev_ratio < 1, "dev_ratio should be in range (0,1)."
-                try:
-                    with open(os.path.join(data_dir, 'train.txt'), 'r', encoding='utf-8') as f, \
-                            open(os.path.join(data_dir, 'middle_file.txt'), 'w', encoding='utf-8') as f1, \
-                            open(os.path.join(data_dir, 'dev.txt'), 'w', encoding='utf-8') as f2:
-                        for line in f:
-                            if random.random() < dev_ratio:
-                                f2.write(line)
-                            else:
-                                f1.write(line)
-                    os.remove(os.path.join(data_dir, 'train.txt'))
-                    os.renames(os.path.join(data_dir, 'middle_file.txt'), os.path.join(data_dir, 'train.txt'))
-                finally:
-                    if os.path.exists(os.path.join(data_dir, 'middle_file.txt')):
-                        os.remove(os.path.join(data_dir, 'middle_file.txt'))
-
-        return data_dir
diff --git a/tests/core/collators/padders/test_numpy_padder.py b/tests/core/collators/padders/test_numpy_padder.py
index 0e93aa21..6c05e00b 100644
--- a/tests/core/collators/padders/test_numpy_padder.py
+++ b/tests/core/collators/padders/test_numpy_padder.py
@@ -8,7 +8,7 @@ from fastNLP.envs.imports import _NEED_IMPORT_TORCH
 
 class TestNumpyNumberPadder:
     def test_run(self):
-        padder = NumpyNumberPadder(ele_dtype=int, dtype=int, pad_val=-1)
+        padder = NumpyNumberPadder(pad_val=-1, ele_dtype=int, dtype=int)
         a = [1, 2, 3]
         assert isinstance(padder(a), np.ndarray)
         assert (padder(a) == np.array(a)).sum() == 3
@@ -17,7 +17,7 @@ class TestNumpyNumberPadder:
 @pytest.mark.torch
 class TestNumpySequencePadder:
     def test_run(self):
-        padder = NumpySequencePadder(ele_dtype=int, dtype=int, pad_val=-1)
+        padder = NumpySequencePadder(pad_val=-1, ele_dtype=int, dtype=int)
         a = [[1, 2, 3], [3]]
         a = padder(a)
         shape = np.shape(a)
@@ -27,18 +27,18 @@ class TestNumpySequencePadder:
         assert (a == b).sum().item() == shape[0]*shape[1]
 
     def test_dtype_check(self):
-        padder = NumpySequencePadder(ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int, pad_val=-1)
+        padder = NumpySequencePadder(pad_val=-1, ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int)
         with pytest.raises(DtypeError):
-            padder = NumpySequencePadder(ele_dtype=str, dtype=int, pad_val=-1)
+            padder = NumpySequencePadder(pad_val=-1, ele_dtype=str, dtype=int)
         if _NEED_IMPORT_TORCH:
             import torch
             with pytest.raises(DtypeError):
-                padder = NumpySequencePadder(ele_dtype=torch.long, dtype=int, pad_val=-1)
+                padder = NumpySequencePadder(pad_val=-1, ele_dtype=torch.long, dtype=int)
 
 
 class TestNumpyTensorPadder:
     def test_run(self):
-        padder = NumpyTensorPadder(ele_dtype=np.zeros(3).dtype, dtype=int, pad_val=-1)
+        padder = NumpyTensorPadder(pad_val=-1, ele_dtype=np.zeros(3).dtype, dtype=int)
         a = [np.zeros(3), np.zeros(2), np.zeros(0)]
         a = padder(a)
         shape = np.shape(a)
@@ -68,15 +68,15 @@ class TestNumpyTensorPadder:
         assert (a == b).sum().item() == shape[0]*shape[1]*shape[2]
 
     def test_dtype_check(self):
-        padder = NumpyTensorPadder(ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int, pad_val=-1)
+        padder = NumpyTensorPadder(pad_val=-1, ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int)
         with pytest.raises(DtypeError):
-            padder = NumpyTensorPadder(ele_dtype=str, dtype=int, pad_val=-1)
+            padder = NumpyTensorPadder(pad_val=-1, ele_dtype=str, dtype=int)
         if _NEED_IMPORT_TORCH:
             import torch
             with pytest.raises(DtypeError):
-                padder = NumpyTensorPadder(ele_dtype=torch.long, dtype=int, pad_val=-1)
+                padder = NumpyTensorPadder(pad_val=-1, ele_dtype=torch.long, dtype=int)
             with pytest.raises(DtypeError):
-                padder = NumpyTensorPadder(ele_dtype=int, dtype=torch.long, pad_val=-1)
+                padder = NumpyTensorPadder(pad_val=-1, ele_dtype=int, dtype=torch.long)
 
 
 
diff --git a/tests/core/collators/padders/test_raw_padder.py b/tests/core/collators/padders/test_raw_padder.py
index 41a9de64..9742bc9a 100644
--- a/tests/core/collators/padders/test_raw_padder.py
+++ b/tests/core/collators/padders/test_raw_padder.py
@@ -7,14 +7,14 @@ from fastNLP.core.collators.padders.exceptions import DtypeError
 
 class TestRawNumberPadder:
     def test_run(self):
-        padder = RawNumberPadder(ele_dtype=int, dtype=int, pad_val=-1)
+        padder = RawNumberPadder(pad_val=-1, ele_dtype=int, dtype=int)
         a = [1, 2, 3]
         assert padder(a) == a
 
 
 class TestRawSequencePadder:
     def test_run(self):
-        padder = RawSequencePadder(ele_dtype=int, dtype=int, pad_val=-1)
+        padder = RawSequencePadder(pad_val=-1, ele_dtype=int, dtype=int)
         a = [[1, 2, 3], [3]]
         a = padder(a)
         shape = np.shape(a)
@@ -24,6 +24,6 @@ class TestRawSequencePadder:
 
     def test_dtype_check(self):
         with pytest.raises(DtypeError):
-            padder = RawSequencePadder(ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int, pad_val=-1)
+            padder = RawSequencePadder(pad_val=-1, ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int)
         with pytest.raises(DtypeError):
-            padder = RawSequencePadder(ele_dtype=str, dtype=int, pad_val=-1)
\ No newline at end of file
+            padder = RawSequencePadder(pad_val=-1, ele_dtype=str, dtype=int)
\ No newline at end of file
diff --git a/tests/core/collators/padders/test_torch_padder.py b/tests/core/collators/padders/test_torch_padder.py
index 0bb363ba..53bd31e3 100644
--- a/tests/core/collators/padders/test_torch_padder.py
+++ b/tests/core/collators/padders/test_torch_padder.py
@@ -12,7 +12,7 @@ if _NEED_IMPORT_TORCH:
 @pytest.mark.torch
 class TestTorchNumberPadder:
     def test_run(self):
-        padder = TorchNumberPadder(ele_dtype=int, dtype=int, pad_val=-1)
+        padder = TorchNumberPadder(pad_val=-1, ele_dtype=int, dtype=int)
         a = [1, 2, 3]
         t_a = padder(a)
         assert isinstance(t_a, torch.Tensor)
@@ -22,7 +22,7 @@ class TestTorchNumberPadder:
 @pytest.mark.torch
 class TestTorchSequencePadder:
     def test_run(self):
-        padder = TorchSequencePadder(ele_dtype=int, dtype=int, pad_val=-1)
+        padder = TorchSequencePadder(pad_val=-1, ele_dtype=int, dtype=int)
         a = [[1, 2, 3], [3]]
         a = padder(a)
         shape = a.shape
@@ -32,20 +32,20 @@ class TestTorchSequencePadder:
         assert (a == b).sum().item() == shape[0]*shape[1]
 
     def test_dtype_check(self):
-        padder = TorchSequencePadder(ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int, pad_val=-1)
+        padder = TorchSequencePadder(pad_val=-1, ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int)
         with pytest.raises(DtypeError):
-            padder = TorchSequencePadder(ele_dtype=str, dtype=int, pad_val=-1)
-        padder = TorchSequencePadder(ele_dtype=torch.long, dtype=int, pad_val=-1)
-        padder = TorchSequencePadder(ele_dtype=np.int8, dtype=None, pad_val=-1)
+            padder = TorchSequencePadder(pad_val=-1, ele_dtype=str, dtype=int)
+        padder = TorchSequencePadder(pad_val=-1, ele_dtype=torch.long, dtype=int)
+        padder = TorchSequencePadder(pad_val=-1, ele_dtype=np.int8, dtype=None)
         a = padder([[1], [2, 322]])
         assert (a>67).sum()==0  # 因为int8的范围为-67 - 66
-        padder = TorchSequencePadder(ele_dtype=np.zeros(2).dtype, dtype=None, pad_val=-1)
+        padder = TorchSequencePadder(pad_val=-1, ele_dtype=np.zeros(2).dtype, dtype=None)
 
 
 @pytest.mark.torch
 class TestTorchTensorPadder:
     def test_run(self):
-        padder = TorchTensorPadder(ele_dtype=torch.zeros(3).dtype, dtype=int, pad_val=-1)
+        padder = TorchTensorPadder(pad_val=-1, ele_dtype=torch.zeros(3).dtype, dtype=int)
         a = [torch.zeros(3), torch.zeros(2), torch.zeros(0)]
         a = padder(a)
         shape = a.shape
@@ -74,7 +74,7 @@ class TestTorchTensorPadder:
                               [[0, -1], [-1, -1], [-1, -1]]])
         assert (a == b).sum().item() == shape[0]*shape[1]*shape[2]
 
-        padder = TorchTensorPadder(ele_dtype=torch.zeros(3).dtype, dtype=int, pad_val=-1)
+        padder = TorchTensorPadder(pad_val=-1, ele_dtype=torch.zeros(3).dtype, dtype=int)
         a = [torch.zeros((3, 2)), torch.zeros((2, 2)), torch.zeros((1, 0))]
         a = padder(a)
         shape = a.shape
@@ -85,7 +85,7 @@ class TestTorchTensorPadder:
                               [[-1, -1], [-1, -1], [-1, -1]]])
         assert (a == b).sum().item() == shape[0]*shape[1]*shape[2]
 
-        padder = TorchTensorPadder(ele_dtype=torch.zeros(3).dtype, dtype=None, pad_val=-1)
+        padder = TorchTensorPadder(pad_val=-1, ele_dtype=torch.zeros(3).dtype, dtype=None)
         a = [np.zeros((3, 2)), np.zeros((2, 2)), np.zeros((1, 0))]
         a = padder(a)
         shape = a.shape
@@ -97,11 +97,11 @@ class TestTorchTensorPadder:
         assert (a == b).sum().item() == shape[0]*shape[1]*shape[2]
 
     def test_dtype_check(self):
-        padder = TorchTensorPadder(ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int, pad_val=-1)
+        padder = TorchTensorPadder(pad_val=-1, ele_dtype=np.zeros(3, dtype=np.int8).dtype, dtype=int)
         with pytest.raises(DtypeError):
-            padder = TorchTensorPadder(ele_dtype=str, dtype=int, pad_val=-1)
-        padder = TorchTensorPadder(ele_dtype=torch.long, dtype=int, pad_val=-1)
-        padder = TorchTensorPadder(ele_dtype=int, dtype=torch.long, pad_val=-1)
+            padder = TorchTensorPadder(pad_val=-1, ele_dtype=str, dtype=int)
+        padder = TorchTensorPadder(pad_val=-1, ele_dtype=torch.long, dtype=int)
+        padder = TorchTensorPadder(pad_val=-1, ele_dtype=int, dtype=torch.long)