CLN: Use assert

Use assert to ensure that dtype is typed correctly

Author: bashtage

pandas/io/stata.py

@@ -1026,9 +1026,7 @@ def __init__(
         self._column_selector_set = False
         self._value_labels_read = False
         self._data_read = False
-        # TODO: Place holder for mypy, is this right?
-        self._dtype = np.dtype("int")
-        self._dtype_setup = False
+        self._dtype = None
         self._lines_read = 0
 
         self._native_byteorder = _set_endianness(sys.byteorder)
@@ -1364,7 +1362,7 @@ def _read_old_header(self, first_char: bytes) -> None:
 
     def _setup_dtype(self) -> np.dtype:
         """Map between numpy and state dtypes"""
-        if self._dtype_setup:
+        if self._dtype is not None:
             return self._dtype
 
         dtypes = []  # Convert struct data types to numpy data type
@@ -1374,7 +1372,6 @@ def _setup_dtype(self) -> np.dtype:
             else:
                 dtypes.append(("s" + str(i), "S" + str(typ)))
         self._dtype = np.dtype(dtypes)
-        self._dtype_setup = True
 
         return self._dtype
 
@@ -1413,6 +1410,7 @@ def _read_value_labels(self) -> None:
         if self.format_version >= 117:
             self.path_or_buf.seek(self.seek_value_labels)
         else:
+            assert self._dtype is not None
             offset = self.nobs * self._dtype.itemsize
             self.path_or_buf.seek(self.data_location + offset)
 
@@ -1549,6 +1547,7 @@ def read(
             self._read_strls()
 
         # Read data
+        assert self._dtype is not None
         dtype = self._dtype
         max_read_len = (self.nobs - self._lines_read) * dtype.itemsize
         read_len = nrows * dtype.itemsize