TYP: Reviewing it the second time as simonjayhawkins suggested

pandas/io/formats/style.py

@@ -25,13 +25,13 @@
 
 from pandas._config import get_option
 
+from pandas._typing import Axis, FrameOrSeries
 from pandas.compat._optional import import_optional_dependency
 from pandas.util._decorators import Appender
 
 from pandas.core.dtypes.common import is_float
 
 import pandas as pd
-from pandas._typing import Axis, FrameOrSeries
 from pandas.api.types import is_dict_like, is_list_like
 import pandas.core.common as com
 from pandas.core.generic import _shared_docs
@@ -51,7 +51,7 @@
 
 
 @contextmanager
-def _mpl(func):
+def _mpl(func: Callable):
     if has_mpl:
         yield plt, colors
     else:
@@ -135,9 +135,9 @@ class Styler:
 
     def __init__(
         self,
-        data,
+        data: FrameOrSeries,
         precision: Optional[int] = None,
-        table_styles=None,
+        table_styles: Union[List[Dict[str, List[Tuple[str, str]]]], None] = None,
         uuid: Optional[str] = None,
         caption: Optional[str] = None,
         table_attributes: Optional[str] = None,
@@ -185,7 +185,7 @@ def default_display_func(x):
             Tuple[int, int], Callable[[Any], str]
         ] = defaultdict(lambda: default_display_func)
 
-    def _repr_html_(self):
+    def _repr_html_(self) -> str:
         """
         Hooks into Jupyter notebook rich display system.
         """
@@ -221,7 +221,7 @@ def to_excel(
         inf_rep: str = "inf",
         verbose: bool = True,
         freeze_panes: Optional[Tuple[int, int]] = None,
-    ):
+    ) -> None:
 
         from pandas.io.formats.excel import ExcelFormatter
 
@@ -245,7 +245,7 @@ def to_excel(
             engine=engine,
         )
 
-    def _translate(self):
+    def _translate(self) -> Dict:
         """
         Convert the DataFrame in `self.data` and the attrs from `_build_styles`
         into a dictionary of {head, body, uuid, cellstyle}.
@@ -265,14 +265,14 @@ def _translate(self):
         BLANK_CLASS = "blank"
         BLANK_VALUE = ""
 
-        def format_attr(pair) -> str:
+        def format_attr(pair: Dict[str, str]) -> str:
             return "{key}={value}".format(**pair)
 
         # for sparsifying a MultiIndex
         idx_lengths = _get_level_lengths(self.index)
         col_lengths = _get_level_lengths(self.columns, hidden_columns)
 
-        cell_context = dict()
+        cell_context: Dict = dict()
 
         n_rlvls = self.data.index.nlevels
         n_clvls = self.data.columns.nlevels
@@ -555,16 +555,18 @@ def render(self, **kwargs) -> str:
         d.update(kwargs)
         return self.template.render(**d)
 
-    def _update_ctx(self, attrs) -> None:
+    def _update_ctx(self, attrs: FrameOrSeries) -> None:
         """
         Update the state of the Styler.
 
         Collects a mapping of {index_label: ['<property>: <value>']}.
 
+        Parameters
+        ----------
         attrs : Series or DataFrame
-        should contain strings of '<property>: <value>;<prop2>: <val2>'
-        Whitespace shouldn't matter and the final trailing ';' shouldn't
-        matter.
+            should contain strings of '<property>: <value>;<prop2>: <val2>'
+            Whitespace shouldn't matter and the final trailing ';' shouldn't
+            matter.
         """
         for row_label, v in attrs.iterrows():
             for col_label, col in v.items():
@@ -573,7 +575,7 @@ def _update_ctx(self, attrs) -> None:
                 for pair in col.rstrip(";").split(";"):
                     self.ctx[(i, j)].append(pair)
 
-    def _copy(self, deepcopy: bool = False):
+    def _copy(self, deepcopy: bool = False) -> "Styler":
         styler = Styler(
             self.data,
             precision=self.precision,
@@ -590,16 +592,16 @@ def _copy(self, deepcopy: bool = False):
             styler._todo = self._todo
         return styler
 
-    def __copy__(self):
+    def __copy__(self) -> "Styler":
         """
         Deep copy by default.
         """
         return self._copy(deepcopy=False)
 
-    def __deepcopy__(self, memo):
+    def __deepcopy__(self, memo) -> "Styler":
         return self._copy(deepcopy=True)
 
-    def clear(self):
+    def clear(self) -> None:
         """
         Reset the styler, removing any previously applied styles.
 
@@ -622,7 +624,9 @@ def _compute(self):
             r = func(self)(*args, **kwargs)
         return r
 
-    def _apply(self, func, axis: Optional[Axis] = 0, subset=None, **kwargs) -> "Styler":
+    def _apply(
+        self, func: Callable, axis: Optional[Axis] = 0, subset=None, **kwargs
+    ) -> "Styler":
         subset = slice(None) if subset is None else subset
         subset = _non_reducing_slice(subset)
         data = self.data.loc[subset]
@@ -655,7 +659,9 @@ def _apply(self, func, axis: Optional[Axis] = 0, subset=None, **kwargs) -> "Styl
         self._update_ctx(result)
         return self
 
-    def apply(self, func, axis: Optional[Axis] = 0, subset=None, **kwargs) -> "Styler":
+    def apply(
+        self, func: Callable, axis: Optional[Axis] = 0, subset=None, **kwargs
+    ) -> "Styler":
         """
         Apply a function column-wise, row-wise, or table-wise.
 
@@ -706,7 +712,7 @@ def apply(self, func, axis: Optional[Axis] = 0, subset=None, **kwargs) -> "Style
         )
         return self
 
-    def _applymap(self, func, subset=None, **kwargs) -> "Styler":
+    def _applymap(self, func: Callable, subset=None, **kwargs) -> "Styler":
         func = partial(func, **kwargs)  # applymap doesn't take kwargs?
         if subset is None:
             subset = pd.IndexSlice[:]
@@ -715,7 +721,7 @@ def _applymap(self, func, subset=None, **kwargs) -> "Styler":
         self._update_ctx(result)
         return self
 
-    def applymap(self, func, subset=None, **kwargs) -> "Styler":
+    def applymap(self, func: Callable, subset=None, **kwargs) -> "Styler":
         """
         Apply a function elementwise.
 
@@ -745,7 +751,12 @@ def applymap(self, func, subset=None, **kwargs) -> "Styler":
         return self
 
     def where(
-        self, cond, value: str, other: Optional[str] = None, subset=None, **kwargs
+        self,
+        cond: Callable,
+        value: str,
+        other: Optional[str] = None,
+        subset=None,
+        **kwargs,
     ) -> "Styler":
         """
         Apply a function elementwise.
@@ -823,7 +834,7 @@ def set_table_attributes(self, attributes: str) -> "Styler":
         self.table_attributes = attributes
         return self
 
-    def export(self) -> List:
+    def export(self) -> List[Tuple[Callable, Tuple, Dict]]:
         """
         Export the styles to applied to the current Styler.
 
@@ -839,7 +850,7 @@ def export(self) -> List:
         """
         return self._todo
 
-    def use(self, styles: List) -> "Styler":
+    def use(self, styles: List[Tuple[Callable, Tuple, Dict]]) -> "Styler":
         """
         Set the styles on the current Styler.
 
@@ -891,7 +902,9 @@ def set_caption(self, caption: str) -> "Styler":
         self.caption = caption
         return self
 
-    def set_table_styles(self, table_styles: List) -> "Styler":
+    def set_table_styles(
+        self, table_styles: List[Dict[str, List[Tuple[str, str]]]]
+    ) -> "Styler":
         """
         Set the table styles on a Styler.
 
@@ -1170,8 +1183,8 @@ def set_properties(self, subset=None, **kwargs) -> "Styler":
     def _bar(
         s,
         align: str,
-        colors,
-        width=100,
+        colors: List[str],
+        width: float = 100,
         vmin: Optional[float] = None,
         vmax: Optional[float] = None,
     ):
@@ -1192,7 +1205,7 @@ def _bar(
         normed = width * (s.to_numpy(dtype=float) - smin) / (smax - smin + 1e-12)
         zero = -width * smin / (smax - smin + 1e-12)
 
-        def css_bar(start, end, color):
+        def css_bar(start: float, end: float, color: str) -> str:
             """
             Generate CSS code to draw a bar from start to end.
             """
@@ -1417,7 +1430,7 @@ class MyStyler(cls):
 
         return MyStyler
 
-    def pipe(self, func, *args, **kwargs):
+    def pipe(self, func: Callable, *args, **kwargs):
         """
         Apply ``func(self, *args, **kwargs)``, and return the result.
 
@@ -1540,7 +1553,9 @@ def _get_level_lengths(index, hidden_elements=None):
     return non_zero_lengths
 
 
-def _maybe_wrap_formatter(formatter, na_rep: Optional[str]):
+def _maybe_wrap_formatter(
+    formatter: Union[Callable, str], na_rep: Optional[str]
+) -> Callable:
     if isinstance(formatter, str):
         formatter_func = lambda x: formatter.format(x)
     elif callable(formatter):