+ .. note:: On Mac OS X, :func:`getgroups` behavior differs somewhat from
+ other Unix platforms. If the Python interpreter was built with a
+ deployment target of :const:`10.5` or earlier, :func:`getgroups` returns
+ the list of effective group ids associated with the current user process;
+ this list is limited to a system-defined number of entries, typically 16,
+ and may be modified by calls to :func:`setgroups` if suitably privileged.
+ If built with a deployment target greater than :const:`10.5`,
+ :func:`getgroups` returns the current group access list for the user
+ associated with the effective user id of the process; the group access
+ list may change over the lifetime of the process, it is not affected by
+ calls to :func:`setgroups`, and its length is not limited to 16. The
+ deployment target value, :const:`MACOSX_DEPLOYMENT_TARGET`, can be
+ obtained with :func:`sysconfig.get_config_var`.
.. function:: initgroups(username, gid)
+ .. note:: On Mac OS X, the length of *groups* may not exceed the
+ system-defined maximum number of effective group ids, typically 16.
+ See the documentation for :func:`getgroups` for cases where it may not
+ return the same group list set by calling setgroups().