updated v3.0.0.rst and fixed tm.assert_produces_warning

Author: pedromfdiogo

doc/source/whatsnew/v3.0.0.rst

@@ -84,6 +84,7 @@ Other enhancements
 - Support passing a :class:`Iterable[Hashable]` input to :meth:`DataFrame.drop_duplicates` (:issue:`59237`)
 - Support reading Stata 102-format (Stata 1) dta files (:issue:`58978`)
 - Support reading Stata 110-format (Stata 7) dta files (:issue:`47176`)
+- :meth:`DataFrame.to_csv` and :meth:`Series.to_csv` now support Python's new-style format strings (e.g., ``"{:.6f}"``) for the ``float_format`` parameter, in addition to old-style ``%`` format strings and callables. This allows for more flexible and modern formatting of floating point numbers when exporting to CSV. (:issue:`49580`, :issue:`61650`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.notable_bug_fixes:

pandas/tests/io/formats/test_to_csv.py

@@ -1,7 +1,6 @@
 import io
 import os
 import sys
-import warnings
 from zipfile import ZipFile
 
 from _csv import Error
@@ -781,8 +780,7 @@ def test_new_style_with_mixed_types():
 
 def test_new_style_with_mixed_types_in_column():
     df = DataFrame({"A": [1.23, "text", 4.56]})
-    with warnings.catch_warnings(record=True):
-        warnings.simplefilter("always")
+    with tm.assert_produces_warning(UserWarning):
         result = df.to_csv(float_format="{:.2f}", lineterminator="\n")
 
     expected = ",A\n0,1.23\n1,text\n2,4.56\n"