DOC: to_csv warns regarding quoting behaviour for floats #14195 (#14228)

Added a small warning that if `float_format` is set then floats will be quoted even if csv.QUOTE_NONNUMERIC is set

Author: tom-bird

doc/source/io.rst

@@ -1481,7 +1481,7 @@ function takes a number of arguments. Only the first is required.
   - ``encoding``: a string representing the encoding to use if the contents are
     non-ASCII, for python versions prior to 3
   - ``line_terminator``: Character sequence denoting line end (default '\\n')
-  - ``quoting``: Set quoting rules as in csv module (default csv.QUOTE_MINIMAL)
+  - ``quoting``: Set quoting rules as in csv module (default csv.QUOTE_MINIMAL). Note that if you have set a `float_format` then floats are converted to strings and csv.QUOTE_NONNUMERIC will treat them as non-numeric
   - ``quotechar``: Character used to quote fields (default '"')
   - ``doublequote``: Control quoting of ``quotechar`` in fields (default True)
   - ``escapechar``: Character used to escape ``sep`` and ``quotechar`` when

pandas/core/frame.py

@@ -1345,7 +1345,9 @@ def to_csv(self, path_or_buf=None, sep=",", na_rep='', float_format=None,
             The newline character or character sequence to use in the output
             file
         quoting : optional constant from csv module
-            defaults to csv.QUOTE_MINIMAL
+            defaults to csv.QUOTE_MINIMAL. If you have set a `float_format`
+            then floats are comverted to strings and thus csv.QUOTE_NONNUMERIC
+            will treat them as non-numeric
         quotechar : string (length 1), default '\"'
             character used to quote fields
         doublequote : boolean, default True