对于这条较长的Python行，PEP8的正确做法是什么？

Question

How should I break down this line so it abides by PEP8?

    assert (sum(map(lambda x: len(x), 
                    (activities,apps,classes,users,verbs))) ==
            Object.query
                  .filter(Object.status != ObjectStatusChoices.DELETED)
                  .count())

Answer 1

If you rewrite things into separate lines, this never comes up.

It also lets you give meaningful names to the intermediate values (which I had to guess at, but presumably you know them), or even refactor bits of logic out into functions (which you can also give meaningful names to).

For example, not changing any of your logic, or even rewriting any of it (except to use len in place of lambda x: len(x) ):

lengths = map(len, (activities,apps,classes,users,verbs))
db_query = Object.query.filter(Object.status != ObjectStatusChoices.DELETED)
assert sum(lengths) == db_query.count()

Answer 2

First of all, keep in mind that there is no single "correct PEP8 answer" to this. I prefer:

in_mem = sum(len(x) for x in (activities,apps,classes,users,verbs))
in_db = Object.query.filter(
                        Object.status != ObjectStatusChoices.DELETED
                        ).count()
assert in_mem == in_db

Definitely if you find yourself with a statement that needs to be split onto five lines, you probably want more statements.