tidy overly complex code

[reidpr]

Split from #1860. Pylint:

• R0902 too-many-instance-attributes
• R0903 too-few-public-methods
• R0904 too-many-public-methods
• R0911 too-many-return-statements
• R0912 too-many-branches
• R0913 too-many-arguments
• R0914 too-many-locals
• R0915 too-many-statements
• R1702 too-many-nested-blocks

Pylint complains a lot about code being too complex. In a lot of cases, I think it’s right and refactoring is warranted. This requires a lot of detailed analysis and this issue itself might best be split.