The docs for the ast module document the '_fields' attribute on AST
instances. Either that documentation needs to go away or the attribute
needs to be renamed as the leading underscore means it is private to the
internal API.

I disagree. The AST classes are auto-generated, the leading underscore
of _fields is there to avoid clashes with field names from the AST types.

This is similar to
http://docs.python.org/dev/library/collections#collections.somenamedtuple._fields
which shouldn't be renamed, but isn't private either.

This is consistent with the methods in named tuples (also to avoid name 
clashes).

I agree with Georg and Raymond, closing this as "won't fix".