transformations.py 文件源码

def deMorganize(a):
    """Apply De Morgan's law throughout the code in order to canonicalize"""
    if not isinstance(a, ast.AST):
        return a
    # We only care about statements beginning with not
    if type(a) == ast.UnaryOp and type(a.op) == ast.Not:
        oper = a.operand
        top = type(oper)

        # not (blah and gah) == (not blah or not gah)
        if top == ast.BoolOp:
            oper.op = negate(oper.op)
            for i in range(len(oper.values)):
                oper.values[i] = deMorganize(negate(oper.values[i]))
            oper.negated = not oper.negated if hasattr(oper, "negated") else True
            transferMetaData(a, oper)
            return oper
        # not a < b == a >= b
        elif top == ast.Compare:
            oper.left = deMorganize(oper.left)
            oper.ops = [negate(oper.ops[0])]
            oper.comparators = [deMorganize(oper.comparators[0])]
            oper.negated = not oper.negated if hasattr(oper, "negated") else True
            transferMetaData(a, oper)
            return oper
        # not not blah == blah
        elif top == ast.UnaryOp and type(oper.op) == ast.Not:
            oper.operand = deMorganize(oper.operand)
            if eventualType(oper.operand) != bool:
                return a
            oper.operand.negated = not oper.operand.negated if hasattr(oper.operand, "negated") else True
            return oper.operand
        elif top == ast.NameConstant:
            if oper.value in [True, False]:
                oper = negate(oper)
                transferMetaData(a, oper)
                return oper
            elif oper.value == None:
                tmp = ast.NameConstant(True)
                transferMetaData(a, tmp)
                tmp.negated = True
                return tmp
            else:
                log("Unknown NameConstant: " + str(oper.value), "bug")

    return applyToChildren(a, deMorganize)

##### CLEANUP FUNCTIONS #####