STYLE: Fix Pylint Style Checks For used-before-assignment (pandas-dev…

…#48940)

* STYLE: Fix Pylint Style Checks For used-before-assignment

* Refactor: Use 'with open' instead of open/close

* CLN: disable used-before-assignment warning

* CLN: Remove used-before-assignment from pyproject.toml

* CLN: disable used-before-assignment warning in-line

pandas/_version.py

@@ -73,8 +73,8 @@ def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False, env=
     assert isinstance(commands, list)
     p = None
     for c in commands:
+        dispcmd = str([c] + args)
         try:
-            dispcmd = str([c] + args)
             # remember shell=False, so use git.cmd on windows, not just git
             p = subprocess.Popen(
                 [c] + args,

pandas/core/arrays/sparse/array.py

@@ -1309,6 +1309,7 @@ def astype(self, dtype: AstypeArg | None = None, copy: bool = True):
                 values = np.array(self)
                 return astype_nansafe(values, dtype=future_dtype)
             else:
+                # pylint: disable-next=used-before-assignment
                 dtype = cast(ExtensionDtype, dtype)
                 cls = dtype.construct_array_type()
                 return cls._from_sequence(self, dtype=dtype, copy=copy)

pandas/core/dtypes/common.py

@@ -260,7 +260,7 @@ def is_scipy_sparse(arr) -> bool:
     """
     global _is_scipy_sparse
 
-    if _is_scipy_sparse is None:
+    if _is_scipy_sparse is None:  # pylint: disable=used-before-assignment
         try:
             from scipy.sparse import issparse as _is_scipy_sparse
         except ImportError:

pandas/core/groupby/indexing.py

@@ -112,6 +112,7 @@ def _positional_selector(self) -> GroupByPositionalSelector:
         4  b  5
         """
         if TYPE_CHECKING:
+            # pylint: disable-next=used-before-assignment
             groupby_self = cast(groupby.GroupBy, self)
         else:
             groupby_self = self

pandas/core/tools/datetimes.py

@@ -1060,7 +1060,7 @@ def to_datetime(
         exact=exact,
         infer_datetime_format=infer_datetime_format,
     )
-
+    # pylint: disable-next=used-before-assignment
     result: Timestamp | NaTType | Series | Index
 
     if isinstance(arg, Timestamp):

pandas/io/formats/style.py

@@ -78,15 +78,14 @@
     has_mpl = True
 except ImportError:
     has_mpl = False
-    no_mpl_message = "{0} requires matplotlib."
 
 
 @contextmanager
 def _mpl(func: Callable) -> Generator[tuple[Any, Any], None, None]:
     if has_mpl:
         yield plt, mpl
     else:
-        raise ImportError(no_mpl_message.format(func.__name__))
+        raise ImportError(f"{func.__name__} requires matplotlib.")
 
 
 ####

pandas/tests/io/excel/test_writers.py

@@ -865,11 +865,10 @@ def test_to_excel_output_encoding(self, ext):
     def test_to_excel_unicode_filename(self, ext):
         with tm.ensure_clean("\u0192u." + ext) as filename:
             try:
-                f = open(filename, "wb")
+                with open(filename, "wb"):
+                    pass
             except UnicodeEncodeError:
                 pytest.skip("No unicode file names on this system")
-            finally:
-                f.close()
 
             df = DataFrame(
                 [[0.123456, 0.234567, 0.567567], [12.32112, 123123.2, 321321.2]],

pandas/tests/io/pytables/test_store.py

@@ -876,13 +876,13 @@ def test_copy():
     with catch_warnings(record=True):
 
         def do_copy(f, new_f=None, keys=None, propindexes=True, **kwargs):
-            try:
-                store = HDFStore(f, "r")
+            if new_f is None:
+                import tempfile
 
-                if new_f is None:
-                    import tempfile
+                fd, new_f = tempfile.mkstemp()
 
-                    fd, new_f = tempfile.mkstemp()
+            try:
+                store = HDFStore(f, "r")
                 tstore = store.copy(new_f, keys=keys, propindexes=propindexes, **kwargs)
 
                 # check keys

pyproject.toml

@@ -75,7 +75,6 @@ disable = [
   "unsubscriptable-object",
   "unsupported-assignment-operation",
   "unsupported-membership-test",
-  "used-before-assignment",
 
  # pylint type "C": convention, for programming standard violation
   "import-outside-toplevel",

versioneer.py

@@ -386,8 +386,8 @@ def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False, env=
     assert isinstance(commands, list)
     p = None
     for c in commands:
+        dispcmd = str([c] + args)
         try:
-            dispcmd = str([c] + args)
             # remember shell=False, so use git.cmd on windows, not just git
             p = subprocess.Popen(
                 [c] + args,