odoo self.ensure_one()

源碼：

def ensure_one(self):
    """ Verifies that the current recorset holds a single record. Raises
    an exception otherwise.
    """
    try:
        # unpack to ensure there is only one value is faster than len when true and
        # has a significant impact as this check is largely called
        _id, = self._ids  # 開始沒明白什么意思，應該是python的多重賦值，只不過這種寫法的情況下等號右邊必須是可迭代的
        return self
    except ValueError:
        raise ValueError("Expected singleton: %s" % self)

 

 

這段代碼如果換種方式就很好理解了：

def ensure_one(self):
        """ 
　　　　　　換種寫法
        """
        if len(self) == 1:
　　　　　　　return self
　　　　　else:
            raise ValueError("Expected singleton: %s" % self)