diff --git a/pandas/io/formats/style.py b/pandas/io/formats/style.py
index 3d9eb4e96f78a..b3eabf3552a75 100644
--- a/pandas/io/formats/style.py
+++ b/pandas/io/formats/style.py
@@ -157,53 +157,40 @@ def __init__(
         na_rep: Optional[str] = None,
         uuid_len: int = 5,
     ):
-        self.ctx: DefaultDict[Tuple[int, int], List[str]] = defaultdict(list)
-        self._todo: List[Tuple[Callable, Tuple, Dict]] = []
-
+        # validate ordered args
         if not isinstance(data, (pd.Series, pd.DataFrame)):
             raise TypeError("``data`` must be a Series or DataFrame")
         if data.ndim == 1:
             data = data.to_frame()
         if not data.index.is_unique or not data.columns.is_unique:
             raise ValueError("style is not supported for non-unique indices.")
-
-        self.data = data
-        self.index = data.index
-        self.columns = data.columns
-
+        assert isinstance(data, DataFrame)
+        self.data: DataFrame = data
+        self.index: pd.Index = data.index
+        self.columns: pd.Index = data.columns
+        if precision is None:
+            precision = get_option("display.precision")
+        self.precision = precision
+        self.table_styles = table_styles
         if not isinstance(uuid_len, int) or not uuid_len >= 0:
             raise TypeError("``uuid_len`` must be an integer in range [0, 32].")
         self.uuid_len = min(32, uuid_len)
         self.uuid = (uuid or uuid4().hex[: self.uuid_len]) + "_"
-        self.table_styles = table_styles
         self.caption = caption
-        if precision is None:
-            precision = get_option("display.precision")
-        self.precision = precision
         self.table_attributes = table_attributes
-        self.hidden_index = False
-        self.hidden_columns: Sequence[int] = []
         self.cell_ids = cell_ids
         self.na_rep = na_rep
 
-        self.tooltips: Optional[_Tooltips] = None
-
+        # assign additional default vars
+        self.hidden_index: bool = False
+        self.hidden_columns: Sequence[int] = []
+        self.ctx: DefaultDict[Tuple[int, int], List[str]] = defaultdict(list)
         self.cell_context: Dict[str, Any] = {}
-
-        # display_funcs maps (row, col) -> formatting function
-
-        def default_display_func(x):
-            if self.na_rep is not None and pd.isna(x):
-                return self.na_rep
-            elif is_float(x):
-                display_format = f"{x:.{self.precision}f}"
-                return display_format
-            else:
-                return x
-
-        self._display_funcs: DefaultDict[
+        self._todo: List[Tuple[Callable, Tuple, Dict]] = []
+        self.tooltips: Optional[_Tooltips] = None
+        self._display_funcs: DefaultDict[  # maps (row, col) -> formatting function
             Tuple[int, int], Callable[[Any], str]
-        ] = defaultdict(lambda: default_display_func)
+        ] = defaultdict(lambda: self._default_display_func)
 
     def _repr_html_(self) -> str:
         """
@@ -224,6 +211,15 @@ def _init_tooltips(self):
         if self.tooltips is None:
             self.tooltips = _Tooltips()
 
+    def _default_display_func(self, x):
+        if self.na_rep is not None and pd.isna(x):
+            return self.na_rep
+        elif is_float(x):
+            display_format = f"{x:.{self.precision}f}"
+            return display_format
+        else:
+            return x
+
     def set_tooltips(self, ttips: DataFrame) -> Styler:
         """
         Add string based tooltips that will appear in the `Styler` HTML result. These