check_subset.py 文件源码

def visit_Num(self, t):
        # -0.0 is distinct from +0.0, but my compiler would mistakenly
        # coalesce the two, if both appear among the constants. Likewise
        # for -0.0 as a component of a complex number. As a hack, instead
        # of handling this case correctly in the compiler, we just forbid
        # it. It's especially unlikely to crop up because the parser even
        # parses -0.0 as UnaryOp(op=USub(), operand=Num(0.0)) -- you'd
        # have to build the AST some other way, to get Num(-0.0).
        assert not has_negzero(t.n), "Negative-zero literals not supported: %r" % (t,)