docs: clarify csv.DictReader's treatment of the first data row (GH-118549)

nedbat · miss-islington · commit b26f72fce200 · 2024-05-03T15:48:34.000Z
(cherry picked from commit 9d67b72) Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>
diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
@@ -156,8 +156,10 @@ The :mod:`csv` module defines the following classes:
 
    The *fieldnames* parameter is a :term:`sequence`.  If *fieldnames* is
    omitted, the values in the first row of file *f* will be used as the
-   fieldnames.  Regardless of how the fieldnames are determined, the
-   dictionary preserves their original ordering.
+   fieldnames and will be omitted from the results. If
+   *fieldnames* is provided, they will be used and the first row will be
+   included in the results.  Regardless of how the fieldnames are determined,
+   the dictionary preserves their original ordering.
 
    If a row has more fields than fieldnames, the remaining data is put in a
    list and stored with the fieldname specified by *restkey* (which defaults
