185 

   186 def _rapply(f, xs):

   187     if xs is None:

   188         # assume None means non-value of optional data

   189         return xs

   190     if isinstance(xs, (list, set, tuple)):

   191         return type(xs)(_rapply(f, x) for x in xs)

   192     if isinstance(xs, dict):

   193         return type(xs)((_rapply(f, k), _rapply(f, v)) for k, v in xs.items())

   194     return f(xs)

   195 

   196 def rapply(f, xs):

   197     """Apply function recursively to every item preserving the data structure

   198 

   199     >>> def f(x):

   200     ...     return 'f(%s)' % x

   201     >>> rapply(f, None) is None

   202     True

   203     >>> rapply(f, 'a')

   204     'f(a)'

   205     >>> rapply(f, {'a'}) == {'f(a)'}

   206     True

   207     >>> rapply(f, ['a', 'b', None, {'c': 'd'}, []])

   208     ['f(a)', 'f(b)', None, {'f(c)': 'f(d)'}, []]

   209 

   210     >>> xs = [object()]

   211     >>> rapply(pycompat.identity, xs) is xs

   212     True

   213     """

   214     if f is pycompat.identity:

   215         # fast path mainly for py2

   216         return xs

   217     return _rapply(f, xs)