It _looks_ like csvwriter.writerow() returns the number of bytes (or is it characters?) written. However, there is no documentation of this:

https://docs.python.org/3.7/library/csv.html#csv.csvwriter.writerow

Is this behavior part of the method's "contract"? And if so, shouldn't we document it?

The same goes for csvwriter.writerows().

Looks like it's bytes written, not characters:

```
>>> import csv
>>> with open('test.csv', 'w', newline='') as csv_file:
...     csv_writer = csv.writer(
...         csv_file,
...         dialect='unix',
...     )
...     csv_writer.writerow('야 너')  # 3 characters
... 
12
```

csvwriter.writerows() does not return anything.

The return value of csv.writecsv() is the return value of the write() method of the file object given as parameter in csv.writer(). I'm not sure it's safe to document it, should we return None instead?

Issue #27497 is related, it adds documentation a return value and documentation to csv.DictWriter.writeheader which uses writerow internally. 

In the discussion, @lsowen found code that uses it at https://docs.djangoproject.com/en/1.9/howto/outputting-csv/#streaming-large-csv-files.

Given that this behavior has been added to csv.DictWriter.writeheader it makes sense to document csv.Writer.writerow. Do you want to post a pull request?

Nope, go ahead.