From 980d0dac23af9e40051799389a0d5bf612f1db70 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <50263213+MomIsBestFriend@users.noreply.github.com>
Date: Fri, 27 Dec 2019 18:02:50 +0200
Subject: [PATCH] TYP: Typing hints in pandas/io/formats/{css,csvs}.py (#30398)

---
 pandas/io/formats/css.py  | 30 +++++++++++++---------
 pandas/io/formats/csvs.py | 52 +++++++++++++++++++--------------------
 2 files changed, 45 insertions(+), 37 deletions(-)

diff --git a/pandas/io/formats/css.py b/pandas/io/formats/css.py
index 583dd49d4c66a..b40d2a57b8106 100644
--- a/pandas/io/formats/css.py
+++ b/pandas/io/formats/css.py
@@ -1,4 +1,5 @@
-"""Utilities for interpreting CSS from Stylers for formatting non-HTML outputs
+"""
+Utilities for interpreting CSS from Stylers for formatting non-HTML outputs.
 """
 
 import re
@@ -6,13 +7,15 @@
 
 
 class CSSWarning(UserWarning):
-    """This CSS syntax cannot currently be parsed"""
+    """
+    This CSS syntax cannot currently be parsed.
+    """
 
     pass
 
 
 def _side_expander(prop_fmt: str):
-    def expand(self, prop, value):
+    def expand(self, prop, value: str):
         tokens = value.split()
         try:
             mapping = self.SIDE_SHORTHANDS[len(tokens)]
@@ -28,12 +31,13 @@ def expand(self, prop, value):
 
 
 class CSSResolver:
-    """A callable for parsing and resolving CSS to atomic properties
-
+    """
+    A callable for parsing and resolving CSS to atomic properties.
     """
 
     def __call__(self, declarations_str, inherited=None):
-        """ the given declarations to atomic properties
+        """
+        The given declarations to atomic properties.
 
         Parameters
         ----------
@@ -46,8 +50,8 @@ def __call__(self, declarations_str, inherited=None):
 
         Returns
         -------
-        props : dict
-            Atomic CSS 2.2 properties
+        dict
+            Atomic CSS 2.2 properties.
 
         Examples
         --------
@@ -69,7 +73,6 @@ def __call__(self, declarations_str, inherited=None):
          ('font-size', '24pt'),
          ('font-weight', 'bold')]
         """
-
         props = dict(self.atomize(self.parse(declarations_str)))
         if inherited is None:
             inherited = {}
@@ -235,10 +238,15 @@ def atomize(self, declarations):
     expand_margin = _side_expander("margin-{:s}")
     expand_padding = _side_expander("padding-{:s}")
 
-    def parse(self, declarations_str):
-        """Generates (prop, value) pairs from declarations
+    def parse(self, declarations_str: str):
+        """
+        Generates (prop, value) pairs from declarations.
 
         In a future version may generate parsed tokens from tinycss/tinycss2
+
+        Parameters
+        ----------
+        declarations_str : str
         """
         for decl in declarations_str.split(";"):
             if not decl.strip():
diff --git a/pandas/io/formats/csvs.py b/pandas/io/formats/csvs.py
index 72ba1a892cb8f..0d581f30e50e7 100644
--- a/pandas/io/formats/csvs.py
+++ b/pandas/io/formats/csvs.py
@@ -5,13 +5,14 @@
 import csv as csvlib
 from io import StringIO
 import os
-from typing import List
+from typing import Hashable, List, Mapping, Optional, Sequence, Union
 import warnings
 from zipfile import ZipFile
 
 import numpy as np
 
 from pandas._libs import writers as libwriters
+from pandas._typing import FilePathOrBuffer
 
 from pandas.core.dtypes.generic import (
     ABCDatetimeIndex,
@@ -33,27 +34,26 @@ class CSVFormatter:
     def __init__(
         self,
         obj,
-        path_or_buf=None,
-        sep=",",
-        na_rep="",
-        float_format=None,
+        path_or_buf: Optional[FilePathOrBuffer[str]] = None,
+        sep: str = ",",
+        na_rep: str = "",
+        float_format: Optional[str] = None,
         cols=None,
-        header=True,
-        index=True,
-        index_label=None,
-        mode="w",
-        encoding=None,
-        compression="infer",
-        quoting=None,
+        header: Union[bool, Sequence[Hashable]] = True,
+        index: bool = True,
+        index_label: Optional[Union[bool, Hashable, Sequence[Hashable]]] = None,
+        mode: str = "w",
+        encoding: Optional[str] = None,
+        compression: Union[str, Mapping[str, str], None] = "infer",
+        quoting: Optional[int] = None,
         line_terminator="\n",
-        chunksize=None,
+        chunksize: Optional[int] = None,
         quotechar='"',
-        date_format=None,
-        doublequote=True,
-        escapechar=None,
+        date_format: Optional[str] = None,
+        doublequote: bool = True,
+        escapechar: Optional[str] = None,
         decimal=".",
     ):
-
         self.obj = obj
 
         if path_or_buf is None:
@@ -154,14 +154,17 @@ def __init__(
         if not index:
             self.nlevels = 0
 
-    def save(self):
+    def save(self) -> None:
         """
-        Create the writer & save
+        Create the writer & save.
         """
         # GH21227 internal compression is not used when file-like passed.
         if self.compression and hasattr(self.path_or_buf, "write"):
-            msg = "compression has no effect when passing file-like object as input."
-            warnings.warn(msg, RuntimeWarning, stacklevel=2)
+            warnings.warn(
+                "compression has no effect when passing file-like object as input.",
+                RuntimeWarning,
+                stacklevel=2,
+            )
 
         # when zip compression is called.
         is_zip = isinstance(self.path_or_buf, ZipFile) or (
@@ -223,7 +226,6 @@ def save(self):
                     _fh.close()
 
     def _save_header(self):
-
         writer = self.writer
         obj = self.obj
         index_label = self.index_label
@@ -303,8 +305,7 @@ def _save_header(self):
                 encoded_labels.extend([""] * len(columns))
                 writer.writerow(encoded_labels)
 
-    def _save(self):
-
+    def _save(self) -> None:
         self._save_header()
 
         nrows = len(self.data_index)
@@ -321,8 +322,7 @@ def _save(self):
 
             self._save_chunk(start_i, end_i)
 
-    def _save_chunk(self, start_i: int, end_i: int):
-
+    def _save_chunk(self, start_i: int, end_i: int) -> None:
         data_index = self.data_index
 
         # create the data for a chunk