Python Flask棉花糖导入错误：无法导入名称字段

几周前我开始学习flask，并遵循flask mega教程。现在我想自己做一些编程，我试图使用flask marshmallow以json格式从数据库返回数据，但我被卡住了。我在说ImportError时出错：无法导入名称字段

这是模型.py模块：

followers = db.Table('followers',
db.Column('follower_id', db.Integer, db.ForeignKey('user.id')),
db.Column('followed_id', db.Integer, db.ForeignKey('user.id')))


class User(UserMixin, db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(64), index=True, unique=True)
email = db.Column(db.String(120), index=True, unique=True)
country = db.Column(db.String(140))
nationality = db.Column(db.String(140))
password_hash = db.Column(db.String(128))
# Definisanje veze sa Post tabelom
posts = db.relationship('Post', backref='author', lazy='dynamic')
about_me = db.Column(db.String(140))
last_seen = db.Column(db.DateTime, default=datetime.utcnow())
# Definisanje veze sa followers tabelom
followed = db.relationship(
    'User', secondary=followers,
    primaryjoin=(followers.c.follower_id == id),
    secondaryjoin=(followers.c.followed_id == id),
    backref=db.backref('followers', lazy='dynamic'), lazy='dynamic')

class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
body = db.Column(db.String(140))
timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))

def __repr__(self):
    return '<Post {}>'.format(self.body)

#Declaring marshmallow ModelSchema
    class UserSchema(ma.ModelSchema):
    class Meta:
        model = User

@app.route('/all_users', methods=['GET'])
def get_all_users():
    users = User.query.all()
    user_schema = UserSchema(many=True)
    out = user_schema.dump(users).data
    return jsonify(out)

我没有包括所有的代码，但我会提供它，如果它是必要的

由于错误消息指向microblog.py和init.py，我的应用程序中也有模块，所以我将包括这两个模块

microblog.py

from app import app, db
from app.models import User, Post


@app.shell_context_processor
def make_shell_context():
    return {'db': db, 'User': User, 'Post': Post}

from flask import Flask
from logging.handlers import RotatingFileHandler
import logging
from config import Config
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow
from flask_migrate import Migrate
from flask_login import LoginManager
from flask_mail import Mail
from flask_bootstrap import Bootstrap
from flask_moment import Moment
import os


'''Inicijalizacija ekstenzija'''
app = Flask(__name__)
app.config.from_object(Config)
db = SQLAlchemy(app)
migrate = Migrate(app, db)
login = LoginManager(app)
login.login_view = 'login'
mail = Mail(app)
bootstrap = Bootstrap(app)
moment = Moment(app)
ma = Marshmallow(app)

from app import routes, models, errors


if not app.debug:

    if not os.path.exists('logs'):
        os.mkdir('logs')
    file_handler = RotatingFileHandler('logs/microblog.log', maxBytes=10240,
                                       backupCount=10)
    file_handler.setFormatter(logging.Formatter(
        '%(asctime)s %(levelname)s: %(message)s [in %(pathname)s:%(lineno)d]'))
    file_handler.setLevel(logging.INFO)
    app.logger.addHandler(file_handler)

    app.logger.setLevel(logging.INFO)
    app.logger.info('Microblog startup')

\uuuu init\uuuuu.py

from app import app, db
from app.models import User, Post


@app.shell_context_processor
def make_shell_context():
    return {'db': db, 'User': User, 'Post': Post}

from flask import Flask
from logging.handlers import RotatingFileHandler
import logging
from config import Config
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow
from flask_migrate import Migrate
from flask_login import LoginManager
from flask_mail import Mail
from flask_bootstrap import Bootstrap
from flask_moment import Moment
import os


'''Inicijalizacija ekstenzija'''
app = Flask(__name__)
app.config.from_object(Config)
db = SQLAlchemy(app)
migrate = Migrate(app, db)
login = LoginManager(app)
login.login_view = 'login'
mail = Mail(app)
bootstrap = Bootstrap(app)
moment = Moment(app)
ma = Marshmallow(app)

from app import routes, models, errors


if not app.debug:

    if not os.path.exists('logs'):
        os.mkdir('logs')
    file_handler = RotatingFileHandler('logs/microblog.log', maxBytes=10240,
                                       backupCount=10)
    file_handler.setFormatter(logging.Formatter(
        '%(asctime)s %(levelname)s: %(message)s [in %(pathname)s:%(lineno)d]'))
    file_handler.setLevel(logging.INFO)
    app.logger.addHandler(file_handler)

    app.logger.setLevel(logging.INFO)
    app.logger.info('Microblog startup')

---

错误不是来自您的代码，而是来自

摇瓶棉花糖

。因此可能存在安装问题。我建议从零开始清理或重新创建一个virtualenv，看看它是如何运行的。是的，问题是flask棉花糖版本。我刚把它降级了，一切都正常了。很高兴你找到了解决问题的方法，如果你能用一个在清晰的virtualenv上使用坏版本以及如何降级到上一个的例子来回答你自己的问题，那对下一个家伙来说将是一件好事。