pandas to_csv: ascii can't encode character

Check the answer here

It's a much simpler solution:

newdf.to_csv('filename.csv', encoding='utf-8')

You have some characters that are not ASCII and therefore cannot be encoded as you are trying to do. I would just use utf-8 as suggested in a comment.

To check which lines are causing the issue you can try something like this:

def is_not_ascii(string):
    return string is not None and any([ord(s) >= 128 for s in string])

df[df[col].apply(is_not_ascii)]

You'll need to specify the column col you are testing.