[issue18219] csv.DictWriter is slow when writing files with large number of columns

New submission from Mikhail Traskin: _dict_to_list method of the csv.DictWriter objects created with extrasaction="raise" uses look-up in the list of field names to check if current row has any unknown fields. This results in O(n^2) execution time and is very slow if there ar

[issue18219] csv.DictWriter is slow when writing files with large number of columns

Mikhail Traskin added the comment: Any way is fine with me. If you prefer to avoid having public filedset property, please use the attached patch. -- Added file: http://bugs.python.org/file30605/csvdictwriter.v2.patch ___ Python tracker <h

[issue18219] csv.DictWriter is slow when writing files with large number of columns

Mikhail Traskin added the comment: > What is the purpose in touching fieldnames [...] Wrapping the fieldnames property and tupleizing it guarantees that fieldnames and _fieldset fields are consistent. Otherwise, having a separate _fieldset field means that someone who is modifying

[issue18219] csv.DictWriter is slow when writing files with large number of columns

Mikhail Traskin added the comment: Peter, thank you for letting me know that views work with list, I was not aware of this. This is indeed the best solution and it also keeps the DictWriter interface unchanged. Terry, attached patch contains the DictWriter change and a test case in