TYP: Upgrade to mypy 0.920 (pandas-dev#44936)

doc/source/whatsnew/v1.4.0.rst

@@ -397,7 +397,7 @@ If installed, we now require:
 +-----------------+-----------------+----------+---------+
 | pytest (dev)    | 6.0             |          |         |
 +-----------------+-----------------+----------+---------+
-| mypy (dev)      | 0.910           |          |    X    |
+| mypy (dev)      | 0.920           |          |    X    |
 +-----------------+-----------------+----------+---------+
 
 For `optional libraries <https://pandas.pydata.org/docs/getting_started/install.html>`_ the general recommendation is to use the latest version.

environment.yml

@@ -24,7 +24,7 @@ dependencies:
   - flake8-bugbear=21.3.2  # used by flake8, find likely bugs
   - flake8-comprehensions=3.1.0  # used by flake8, linting of unnecessary comprehensions
   - isort>=5.2.1  # check that imports are in the right order
-  - mypy=0.910
+  - mypy=0.920
   - pre-commit>=2.9.2
   - pycodestyle  # used by flake8
   - pyupgrade

pandas/compat/pickle_compat.py

@@ -194,8 +194,8 @@ def __new__(cls) -> DataFrame:  # type: ignore[misc]
 # our Unpickler sub-class to override methods and some dispatcher
 # functions for compat and uses a non-public class of the pickle module.
 
-# error: Name 'pkl._Unpickler' is not defined
-class Unpickler(pkl._Unpickler):  # type: ignore[name-defined]
+
+class Unpickler(pkl._Unpickler):
     def find_class(self, module, name):
         # override superclass
         key = (module, name)
@@ -266,7 +266,8 @@ def load(fh, encoding: str | None = None, is_verbose: bool = False):
             up = Unpickler(fh, encoding=encoding)
         else:
             up = Unpickler(fh)
-        up.is_verbose = is_verbose
+        # "Unpickler" has no attribute "is_verbose"  [attr-defined]
+        up.is_verbose = is_verbose  # type: ignore[attr-defined]
 
         return up.load()
     except (ValueError, TypeError):

pandas/core/base.py

@@ -527,10 +527,7 @@ def to_numpy(
               dtype='datetime64[ns]')
         """
         if is_extension_array_dtype(self.dtype):
-            # error: Too many arguments for "to_numpy" of "ExtensionArray"
-            return self.array.to_numpy(  # type: ignore[call-arg]
-                dtype, copy=copy, na_value=na_value, **kwargs
-            )
+            return self.array.to_numpy(dtype, copy=copy, na_value=na_value, **kwargs)
         elif kwargs:
             bad_keys = list(kwargs.keys())[0]
             raise TypeError(

pandas/core/frame.py

@@ -2634,8 +2634,7 @@ def to_stata(
             # Specifying the version is only supported for UTF8 (118 or 119)
             kwargs["version"] = version
 
-        # mypy: Too many arguments for "StataWriter"
-        writer = statawriter(  # type: ignore[call-arg]
+        writer = statawriter(
             path,
             self,
             convert_dates=convert_dates,

pandas/core/indexes/base.py

@@ -443,7 +443,9 @@ def __new__(
             return Index._simple_new(data, name=name)
 
         elif is_ea_or_datetimelike_dtype(data_dtype):
-            klass = cls._dtype_to_subclass(data_dtype)
+            # Argument 1 to "_dtype_to_subclass" of "Index" has incompatible type
+            # "Optional[Any]"; expected "Union[dtype[Any], ExtensionDtype]"  [arg-type]
+            klass = cls._dtype_to_subclass(data_dtype)  # type: ignore[arg-type]
             if klass is not Index:
                 result = klass(data, copy=copy, name=name, **kwargs)
                 if dtype is not None:

pandas/core/indexes/multi.py

@@ -327,7 +327,9 @@ def __new__(
         result._set_levels(levels, copy=copy, validate=False)
         result._set_codes(codes, copy=copy, validate=False)
 
-        result._names = [None] * len(levels)
+        # Incompatible types in assignment (expression has type "List[None]",
+        # variable has type "FrozenList")  [assignment]
+        result._names = [None] * len(levels)  # type: ignore[assignment]
         if names is not None:
             # handles name validation
             result._set_names(names)

pandas/core/window/rolling.py

@@ -1127,7 +1127,10 @@ def _apply(
         -------
         y : type of input
         """
-        window = self._scipy_weight_generator(self.window, **kwargs)
+        # "None" not callable  [misc]
+        window = self._scipy_weight_generator(  # type: ignore[misc]
+            self.window, **kwargs
+        )
         offset = (len(window) - 1) // 2 if self.center else 0
 
         def homogeneous_func(values: np.ndarray):

pandas/io/common.py

@@ -714,12 +714,10 @@ def get_handle(
 
         # BZ Compression
         elif compression == "bz2":
-            handle = bz2.BZ2File(
-                # Argument 1 to "BZ2File" has incompatible type "Union[str,
-                # Union[IO[Any], RawIOBase, BufferedIOBase, TextIOBase, TextIOWrapper,
-                # mmap]]"; expected "Union[Union[str, bytes, _PathLike[str],
-                # _PathLike[bytes]], IO[bytes]]"
-                handle,  # type: ignore[arg-type]
+            # No overload variant of "BZ2File" matches argument types
+            # "Union[str, BaseBuffer]", "str", "Dict[str, Any]"
+            handle = bz2.BZ2File(  # type: ignore[call-overload]
+                handle,
                 mode=ioargs.mode,
                 **compression_args,
             )

pandas/io/parsers/readers.py

@@ -1170,8 +1170,7 @@ def _make_engine(self, engine="c"):
             raise ValueError(
                 f"Unknown engine: {engine} (valid options are {mapping.keys()})"
             )
-        # error: Too many arguments for "ParserBase"
-        return mapping[engine](self.f, **self.options)  # type: ignore[call-arg]
+        return mapping[engine](self.f, **self.options)
 
     def _failover_to_python(self):
         raise AbstractMethodError(self)

pandas/io/pytables.py

@@ -3351,8 +3351,11 @@ def validate(self, other):
             if sv != ov:
 
                 # show the error for the specific axes
-                for i, sax in enumerate(sv):
-                    oax = ov[i]
+                # Argument 1 to "enumerate" has incompatible type
+                # "Optional[Any]"; expected "Iterable[Any]"  [arg-type]
+                for i, sax in enumerate(sv):  # type: ignore[arg-type]
+                    # Value of type "Optional[Any]" is not indexable  [index]
+                    oax = ov[i]  # type: ignore[index]
                     if sax != oax:
                         raise ValueError(
                             f"invalid combination of [{c}] on appending data "
@@ -3592,7 +3595,9 @@ def f(i, c):
             # TODO: why kind_attr here?
             values = getattr(table_attrs, f"{adj_name}_kind", None)
             dtype = getattr(table_attrs, f"{adj_name}_dtype", None)
-            kind = _dtype_to_kind(dtype)
+            # Argument 1 to "_dtype_to_kind" has incompatible type
+            # "Optional[Any]"; expected "str"  [arg-type]
+            kind = _dtype_to_kind(dtype)  # type: ignore[arg-type]
 
             md = self.read_metadata(c)
             # TODO: figure out why these two versions of `meta` dont always match.

pandas/plotting/_matplotlib/core.py

@@ -1671,9 +1671,7 @@ def blank_labeler(label, value):
             if labels is not None:
                 blabels = [blank_labeler(left, value) for left, value in zip(labels, y)]
             else:
-                # error: Incompatible types in assignment (expression has type "None",
-                # variable has type "List[Any]")
-                blabels = None  # type: ignore[assignment]
+                blabels = None
             results = ax.pie(y, labels=blabels, **kwds)
 
             if kwds.get("autopct", None) is not None:

requirements-dev.txt

@@ -12,7 +12,7 @@ flake8==3.9.2
 flake8-bugbear==21.3.2
 flake8-comprehensions==3.1.0
 isort>=5.2.1
-mypy==0.910
+mypy==0.920
 pre-commit>=2.9.2
 pycodestyle
 pyupgrade