1. 修复DataSet.delete_instance的bug; 2. FieldArray中支持只使用第一个instance推断dimension和type，节省时间

fastNLP/core/field.py

@@ -23,7 +23,8 @@ class AppendToTargetOrInputException(Exception):
         self.field_name = field_name # 标示当前field的名称
 
 class FieldArray:
-    def __init__(self, name, content, is_target=False, is_input=False, padder=None, ignore_type=False):
+    def __init__(self, name, content, is_target=False, is_input=False, padder=None, ignore_type=False,
+                 use_1st_ins_infer_dim_type=True):
         if len(content)==0:
             raise RuntimeError("Empty fieldarray is not allowed.")
         _content = content
@@ -38,6 +39,7 @@ class FieldArray:
         #  根据input的情况设置input，target等
         self._cell_ndim = None  # 多少维度
         self.dtype = None  # 最内层的element都是什么类型的
+        self._use_1st_ins_infer_dim_type = bool(use_1st_ins_infer_dim_type)
         self._is_input = False
         self._is_target = False
 
@@ -77,7 +79,7 @@ class FieldArray:
         if value is True and \
                 self._is_target is False and \
                 self._ignore_type is False:
-            self._check_dtype_and_ndim()
+            self._check_dtype_and_ndim(only_check_1st_ins_dim_type=self._use_1st_ins_infer_dim_type)
         if value is False and self._is_target is False:
             self.dtype = None
             self._cell_ndim = None
@@ -95,32 +97,34 @@ class FieldArray:
         if value is True and \
                 self._is_input is False and \
                 self._ignore_type is False:
-            self._check_dtype_and_ndim()
+            self._check_dtype_and_ndim(only_check_1st_ins_dim_type=self._use_1st_ins_infer_dim_type)
         if value is False and self._is_input is False:
             self.dtype = None
             self._cell_ndim = None
         self._is_target = value
 
-    def _check_dtype_and_ndim(self):
+    def _check_dtype_and_ndim(self, only_check_1st_ins_dim_type=True):
         """
         检查当前content所有的element是否是同一个类型，且是否每个元素具有相同的维度。通过的话，设置_cell_ndim与_ele_type属性；没有
             通过将直接报错.
 
+        :param bool only_check_1st_ins_dim_type: 是否只检查第一个元素的type和dim
         :return:
         """
         cell_0 = self.content[0]
         index = 0
         try:
             type_0, dim_0 = _get_ele_type_and_dim(cell_0)
-            for cell in self.content[1:]:
-                index += 1
-                type_i, dim_i = _get_ele_type_and_dim(cell)
-                if type_i!=type_0:
-                    raise SetInputOrTargetException("Type:{} in index {} is different from the first element with type:{}."
-                                                    ".".format(type_i, index, type_0))
-                if dim_0!=dim_i:
-                    raise SetInputOrTargetException("Dimension:{} in index {} is different from the first element with "
-                                                    "dimension:{}.".format(dim_i, index, dim_0))
+            if not only_check_1st_ins_dim_type:
+                for cell in self.content[1:]:
+                    index += 1
+                    type_i, dim_i = _get_ele_type_and_dim(cell)
+                    if type_i!=type_0:
+                        raise SetInputOrTargetException("Type:{} in index {} is different from the first element with type:{}."
+                                                        ".".format(type_i, index, type_0))
+                    if dim_0!=dim_i:
+                        raise SetInputOrTargetException("Dimension:{} in index {} is different from the first element with "
+                                                        "dimension:{}.".format(dim_i, index, dim_0))
             self._cell_ndim = dim_0
             self.dtype = type_0
         except SetInputOrTargetException as e:
@@ -132,7 +136,7 @@ class FieldArray:
         :param val: 把该val append到fieldarray。
         :return:
         """
-        if (self._is_target or self._is_input) and self._ignore_type is False:
+        if (self._is_target or self._is_input) and self._ignore_type is False and not self._use_1st_ins_infer_dim_type:
             type_, dim_ = _get_ele_type_and_dim(val)
             if self.dtype!=type_:
                 raise AppendToTargetOrInputException(f"Value(type:{type_}) are of different types with "
@@ -144,6 +148,14 @@ class FieldArray:
         else:
             self.content.append(val)
 
+    def pop(self, index):
+        """
+        删除该field中index处的元素
+        :param int index: 从0开始的数据下标。
+        :return:
+        """
+        self.content.pop(index)
+
     def __getitem__(self, indices):
         return self.get(indices, pad=False)