Blank line Python PEP8 best practice in class definition

This is really a matter of taste. I personally include the blank line to be consisted with classes which have a docstring. Quoting PEP-0257:

Insert a blank line before and after all docstrings (one-line or multi-line) that document a class -- generally speaking, the class's methods are separated from each other by a single blank line, and the docstring needs to be offset from the first method by a blank line; for symmetry, put a blank line between the class header and the docstring.

To illustrate:

class WithoutDocString(object):

    def __init__(self):
        pass


class WithADocString(object):

    """Summary line.

    Bla bla bla bla.
    """

    def __init__(self):
        pass

As I understand the blank line section of PEP-8, there is some liberty on this question. Blank lines may appear in some places (separating groups of related functions) and may be omitted in other places (to group a list of one-liners).

There is no liberty, however, about blank lines after definition headers. They should not appear, conforming to the PEP-8 rules.

Your PEP-8 compliance checker does not seem to check this, though.

Generally (not PEP-8 related), I have the feeling that blank lines, as many other formatting issues, is a matter of what you are used to. There are no scientific researches I know of that show which formatting works best on unbiased developers. And most of us are biased anyway, so even this probably would not mean very much.

When editing existing code, my main approach always is to stick to the existing formatting. But that's beside the point here ;-)