Each line of text in your code should be at most 100 characters long.
There has been lots of discussion about this rule and the decision remains that 100 characters is the maximum.
Exception: if a comment line contains an example command or a literal URL longer than 100 characters, that line may be longer than 100 characters for ease of cut and paste.
Exception: import lines can go over the limit because humans rarely see them. This also simplifies tool writing.