nodes.py 文件源码

def __init__(self, *fields, **attributes):
        if self.abstract:
            raise TypeError('abstract nodes are not instanciable')
        if fields:
            if len(fields) != len(self.fields):
                if not self.fields:
                    raise TypeError('%r takes 0 arguments' %
                                    self.__class__.__name__)
                raise TypeError('%r takes 0 or %d argument%s' % (
                    self.__class__.__name__,
                    len(self.fields),
                    len(self.fields) != 1 and 's' or ''
                ))
            for name, arg in izip(self.fields, fields):
                setattr(self, name, arg)
        for attr in self.attributes:
            setattr(self, attr, attributes.pop(attr, None))
        if attributes:
            raise TypeError('unknown attribute %r' %
                            next(iter(attributes)))