PEP 8 suggests lines should be limited to 79 characters. This is because it allows you to have multiple files open next to one another, while also avoiding line wrapping. Of course, keeping statements to 79 characters or less is not always possible. PEP 8 outlines ways to allow statements to run over several lines.
If the code is contained in parentheses, Python will assume line continuation and you can just go to the next line:
If line breaking needs to occur around binary operators, like + and *, it should occur before the operator. This rule stems from mathematics.
Breaking before binary operators produces more readable code, so PEP 8 encourages it. Code that consistently breaks after a binary operator is still PEP 8 compliant. However, you’re encouraged to break before a binary operator.