def Assign(target, source):
    """Build an assignment statement"""
    if not isinstance(target, list):
        target = [target]
    if not isinstance(source, list):
        source.prefix = u" "
        source = [source]

    return Node(syms.atom,
                target + [Leaf(token.EQUAL, u"=", prefix=u" ")] + source)
Build an assignment statement