What is the recommended way to break long if statement? (W504 line break after binary operator)

Question

What is currently the recommended way to break a long line of if statement with "and" and "or" operators?

1st option

With the style below (which is from PEP8) with flake8 I'm getting warnings: W504 line break after binary operator:

if (this_is_one_thing and
    that_is_another_thing):
    do_something()

2nd option

if (this_is_one_thing
    and that_is_another_thing):
    do_something()

Now I'm getting the warning W503 line break before the binary operator. The second seems to be in line with this recommendation from PEP8

I tried to find an answer but I'm still unsure. I think maybe using 2nd option and disabling the W503 warning will be a way to deal with this problem?

Answer 1

If we consult the documentation on flake 8 we see:

Anti-pattern

Note: Despite being in the anti-pattern section, this will soon be considered the best practice.

income = (gross_wages
          + taxable_interest)

Best practice

Note: Despite being in the best practice section, this will soon be considered an anti-pattern.

income = (gross_wages +
          taxable_interest)

So the line break before the binary operator will be considered best practice.

The documentation for W504, advices the operator before the new line as best practice, without the given note:

Anti-pattern

income = (gross_wages +
          taxable_interest)

Best practice

income = (gross_wages
          + taxable_interest)

Answer 2

When in doubt, ask Black:

if (                                                           
    this_is_one_thing
    and that_is_another_thing
):                                                             
    do_something()                                             

For a long time, PEP-8 recommended breaking after a binary operator, but they have "recently" switched to the Donald-Knuth-approved break-before-binary-operator style.

Answer 3

instead and or or you can use all or any:

if all(
        this_is_one_thing,
        that_is_another_thing):
    do_something()

Answer 4

Flake8 is one of the Python lints, and the full list of errors can be found useful to find anti-patterns and best practices for each specific error.