expressions.py 文件源码

def __init__(self, condition=None, then=None, **lookups):
        if lookups and condition is None:
            condition, lookups = Q(**lookups), None
        if condition is None or not isinstance(condition, Q) or lookups:
            raise TypeError("__init__() takes either a Q object or lookups as keyword arguments")
        super(When, self).__init__(output_field=None)
        self.condition = condition
        self.result = self._parse_expressions(then)[0]