Patch #1635454: the csv.DictWriter class now includes the offending
field names in its exception message if you try to write a record with
a dictionary containing fields not in the CSV field names list.
diff --git a/Lib/csv.py b/Lib/csv.py
index f213854..8c6b740 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -115,9 +115,10 @@
def _dict_to_list(self, rowdict):
if self.extrasaction == "raise":
- for k in rowdict.keys():
- if k not in self.fieldnames:
- raise ValueError, "dict contains fields not in fieldnames"
+ wrong_fields = [k for k in rowdict if k not in self.fieldnames]
+ if wrong_fields:
+ raise ValueError("dict contains fields not in fieldnames: " +
+ ", ".join(wrong_fields))
return [rowdict.get(key, self.restval) for key in self.fieldnames]
def writerow(self, rowdict):