Fix a few tests, want to make sure it'll be approved if the tests are good before fixing everything

Author: ben-cutler-tamarin

pandas/core/tools/datetimes.py

@@ -33,7 +33,6 @@
 )
 from pandas._libs.tslibs.conversion import cast_from_unit_vectorized
 from pandas._libs.tslibs.dtypes import NpyDatetimeUnit
-from pandas._libs.tslibs.nattype import NaTType
 from pandas._libs.tslibs.parsing import (
     DateParseError,
     guess_datetime_format,
@@ -86,7 +85,7 @@
         Callable,
         Hashable,
     )
-
+    from pandas._libs.tslibs.nattype import NaTType
     from pandas._libs.tslibs.timedeltas import UnitChoices
 
     from pandas import (
@@ -153,7 +152,7 @@ def _guess_datetime_format_for_array(
             [
                 datetime.strptime(date_string, fmt)
                 for date_string in arr
-                if date_string and not isinstance(date_string, NaTType)
+                if date_string and isinstance(date_string, str)
             ]
             return fmt
         except ValueError:

pandas/tests/tools/test_to_datetime.py

@@ -1429,10 +1429,7 @@ def test_datetime_invalid_index(self, values, format):
         else:
             warn = None
 
-        with tm.assert_produces_warning(
-            warn, match="Could not infer format", raise_on_extra_warnings=False
-        ):
-            res = to_datetime(values, errors="coerce", format=format)
+        res = to_datetime(values, errors="coerce", format=format)
         tm.assert_index_equal(res, DatetimeIndex([NaT] * len(values)))
 
         msg = "|".join(
@@ -1628,13 +1625,10 @@ def test_to_datetime_malformed_raise(self):
             ValueError,
             match=msg,
         ):
-            with tm.assert_produces_warning(
-                UserWarning, match="Could not infer format"
-            ):
-                to_datetime(
-                    ts_strings,
-                    errors="raise",
-                )
+            to_datetime(
+                ts_strings,
+                errors="raise",
+            )
 
     def test_iso_8601_strings_with_same_offset(self):
         # GH 17697, 11736

pandas/tests/tslibs/test_parsing.py

@@ -232,10 +232,7 @@ def test_parsers_month_freq(date_str, expected):
     ],
 )
 def test_guess_datetime_format_with_parseable_formats(string, fmt):
-    with tm.maybe_produces_warning(
-        UserWarning, fmt is not None and re.search(r"%d.*%m", fmt)
-    ):
-        result = parsing.guess_datetime_format(string)
+    result = parsing.guess_datetime_format(string)
     assert result == fmt
 
 
@@ -292,31 +289,25 @@ def test_guess_datetime_format_wrong_type_inputs(invalid_type_dt):
 
 
 @pytest.mark.parametrize(
-    "string,fmt,dayfirst,warning",
+    "string,fmt,dayfirst",
     [
-        ("2011-1-1", "%Y-%m-%d", False, None),
-        ("2011-1-1", "%Y-%d-%m", True, None),
-        ("1/1/2011", "%m/%d/%Y", False, None),
-        ("1/1/2011", "%d/%m/%Y", True, None),
-        ("30-1-2011", "%d-%m-%Y", False, UserWarning),
-        ("30-1-2011", "%d-%m-%Y", True, None),
-        ("2011-1-1 0:0:0", "%Y-%m-%d %H:%M:%S", False, None),
-        ("2011-1-1 0:0:0", "%Y-%d-%m %H:%M:%S", True, None),
-        ("2011-1-3T00:00:0", "%Y-%m-%dT%H:%M:%S", False, None),
-        ("2011-1-3T00:00:0", "%Y-%d-%mT%H:%M:%S", True, None),
-        ("2011-1-1 00:00:00", "%Y-%m-%d %H:%M:%S", False, None),
-        ("2011-1-1 00:00:00", "%Y-%d-%m %H:%M:%S", True, None),
+        ("2011-1-1", "%Y-%m-%d", False),
+        ("2011-1-1", "%Y-%d-%m", True),
+        ("1/1/2011", "%m/%d/%Y", False),
+        ("1/1/2011", "%d/%m/%Y", True),
+        ("30-1-2011", "%d-%m-%Y", False),
+        ("30-1-2011", "%d-%m-%Y", True),
+        ("2011-1-1 0:0:0", "%Y-%m-%d %H:%M:%S", False),
+        ("2011-1-1 0:0:0", "%Y-%d-%m %H:%M:%S", True),
+        ("2011-1-3T00:00:0", "%Y-%m-%dT%H:%M:%S", False),
+        ("2011-1-3T00:00:0", "%Y-%d-%mT%H:%M:%S", True),
+        ("2011-1-1 00:00:00", "%Y-%m-%d %H:%M:%S", False),
+        ("2011-1-1 00:00:00", "%Y-%d-%m %H:%M:%S", True),
     ],
 )
-def test_guess_datetime_format_no_padding(string, fmt, dayfirst, warning):
+def test_guess_datetime_format_no_padding(string, fmt, dayfirst):
     # see gh-11142
-    msg = (
-        rf"Parsing dates in {fmt} format when dayfirst=False \(the default\) "
-        "was specified. "
-        "Pass `dayfirst=True` or specify a format to silence this warning."
-    )
-    with tm.assert_produces_warning(warning, match=msg):
-        result = parsing.guess_datetime_format(string, dayfirst=dayfirst)
+    result = parsing.guess_datetime_format(string, dayfirst=dayfirst)
     assert result == fmt