Use an optional argument in a behave phrase.

behave_optional_argument

from behave.matchers import register_type


def parse_optional(text):
    return text.strip()

# https://pypi.python.org/pypi/parse#custom-type-conversions
parse_optional.pattern = r'\s?\w*\s?'

register_type(optional=parse_optional)


@step(u'I find a{n:optional}{active:optional} "{model_name}" with {domain}')
def impl(ctx, n, active, model_name, domain):
    assert active in ('', 'inactive', 'active', 'possibly inactive')

# phrases
# Given I find a "res.users" with login: test
# Given I find an inactive "res.users" with login: test
# Given I find an active "res.users" with login: test
# Given I find a possibly inactive "res.users" with login: test

Also note that behave's may have changed since I wrote this gist.

I switch domain2_browser to 1st position, and it works!
e.g.
def impl(ctx, domain2_browser, state):

@huyenuet I guess you are using pycharm. One issue I am facing when using optional part is steps are passing but I am not able to navigate to the steps as they are showing as undefined. Are you facing this issue ?

@guewen yeah i was referring to variable parameter and Thanks @huyenuet for the answer