dimensions.py 文件源码

def __new__(cls, name, symbol=None):

        if isinstance(name, string_types):
            name = Symbol(name)
        else:
            name = sympify(name)

        if not isinstance(name, Expr):
            raise TypeError("Dimension name needs to be a valid math expression")

        if isinstance(symbol, string_types):
            symbol = Symbol(symbol)
        elif symbol is not None:
            assert isinstance(symbol, Symbol)

        if symbol is not None:
            obj = Expr.__new__(cls, name, symbol)
        else:
            obj = Expr.__new__(cls, name)

        obj._name = name
        obj._symbol = symbol
        return obj