如何在Python中获取Model内对象列表的值？（一对多关系场景）

Hey there! I see you're working with a one-to-many relationship between User and Friend models, and you're stuck with those generic <models.Friend object at ...> references when printing the friends field. Let's fix that so you can see actual, meaningful data instead.

方法1：遍历关系列表，提取具体属性 #

Since record.friends is a list of Friend model instances, you can loop through each one and access its individual attributes (like id, name, or whatever fields you've defined on the Friend model). Here's a clean way to format the data with a list comprehension:

record = User.query.filter_by(id=7).first()
# 替换成你的Friend模型实际拥有的字段，比如id、name、email等
formatted_friends = [{"id": friend.id, "name": friend.name} for friend in record.friends]
# 现在打印就能看到具体值了
print('|{}|{}|{}'.format(record.rfc, record.name, formatted_friends))

方法2：自定义Friend模型的__repr__方法 #

If you want the default print output of Friend objects to show useful details instead of memory addresses, you can override the __repr__ method in your Friend model. This will make any print of a Friend instance (or list of instances) display the info you care about automatically:

from flask_sqlalchemy import SQLAlchemy  # 或者你使用的SQLAlchemy导入方式

db = SQLAlchemy()

class Friend(db.Model):
    __tablename__ = 'friends'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100))
    # 其他字段...
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'))  # 关联User的外键

    def __repr__(self):
        # 自定义显示内容，替换成你的实际字段
        return f"<Friend id={self.id} name='{self.name}'>"

After adding this, your original print statement will output something like:

|BDS344XX3343|Bob|[, ]

为什么会显示对象引用？ #

By default, printing a Python object shows its class name and memory address. SQLAlchemy relationship attributes return lists of model instances, which is why you're seeing those <models.Friend object ...> entries. The two methods above let you either explicitly extract the data you need, or change how the objects are displayed by default.

内容的提问来源于stack exchange，提问作者Alex