Flask 应用程序崩溃（很可能是由于循环导入）

Question

我在这里遵循了本教程： https: //youtu.be/mISFEwojJmE?t =367 。这是一个非常简单的 Flask 应用程序，用于为站点创建用户登录和注册页面。到目前为止，本教程中的一切正常：在我的项目中的脚本中导入对象时，我收到此错误。

错误：

flask.cli.NoAppException
flask.cli.NoAppException: While importing "app", an ImportError was raised:

Traceback (most recent call last):
  File "c:\users\dejar\onedrive\coding\themes & applications\002 static template\install\env\lib\site-packages\flask\cli.py", line 240, in locate_app
    __import__(module_name)
  File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\app.py", line 6, in <module>
    from account import routes
  File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\account\routes.py", line 5, in <module>
    from app import app, now
ImportError: cannot import name 'app' from partially initialized module 'app' (most likely due to a circular import) (C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\app.py)

Traceback (most recent call last)
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\app.py", line 6, in <module>
from account import routes
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\account\routes.py", line 5, in <module>
from app import app, now
During handling of the above exception, another exception occurred:
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\cli.py", line 338, in __call__
self._flush_bg_loading_exception()
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\cli.py", line 326, in _flush_bg_loading_exception
reraise(*exc_info)
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\_compat.py", line 39, in reraise
raise value
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\cli.py", line 314, in _load_app
self._load_unlocked()
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\cli.py", line 330, in _load_unlocked
self._app = rv = self.loader()
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\cli.py", line 388, in load_app
app = locate_app(self, import_name, name)
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\env\Lib\site-packages\flask\cli.py", line 245, in locate_app
raise NoAppException(
flask.cli.NoAppException: While importing "app", an ImportError was raised:

Traceback (most recent call last):
File "c:\users\dejar\onedrive\coding\themes & applications\002 static template\install\env\lib\site-packages\flask\cli.py", line 240, in locate_app
__import__(module_name)
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\app.py", line 6, in <module>
from account import routes
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\account\routes.py", line 5, in <module>
from app import app, now
ImportError: cannot import name 'app' from partially initialized module 'app' (most likely due to a circular import) (C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\app.py)
The debugger caught an exception in your WSGI application. You can now look at the traceback which led to the error.
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You can execute arbitrary Python code in the stack frames and there are some extra helpers available for introspection:

dump() shows all variables in the frame
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我没有发布我的实际应用程序，而是返回并复制了他的应用程序，直到教程中为止，该应用程序在他的 Mac 上运行。但抛出与我在我的电脑上运行的实际应用程序相同的错误。我还尝试以管理员身份从 VS Code 和命令行使用我的环境。这里是：

文件结构

C:.Root directory for the project
|   app.py
|   tree.txt
|   
+---env
......more evn files and folders
|           
+---static
|   +---css
|   |       normalize.css
|   |       styles.css
|   |       
|   \---js
|           jquery.js
|           
+---templates
|       base.html
|       dashboard.html
|       home.html
|       
+---user
|   |   models.py
|   |   routes.py
|   |   __init__.py
|   |   
|   \---__pycache__
|           routes.cpython-38.pyc
|           __init__.cpython-38.pyc
|           
\---__pycache__
        app.cpython-38.pyc

应用程序.py

from flask import Flask, render_template

# account routes
from user import routes

# create and configure the app, an instance of Flask
app = Flask(__name__)


@app.route("/")
def home():
    return render_template("home.html")


@app.route("/dashboard/")
def dashboard():
    return render_template("dashboard.html")

模型.py

from flask import Flask, jsonify


class User:
    def signup(self):
        user = {"_id": "", "name": "", "email": "", "password": ""}
        return jsonify(user), 200
        # if successful, return status code 200 in json format

路线.py

from flask import Flask, render_template

# import the instance of app from app.py
# from file/module import instance
from app import app

# from folder.file import class
from user.models import User


@app.route("/user/signup", methods=["GET"])
def signup():
    return User().signup()

注意：init .py 文件为空

Answer 1

错误消息cannot import name \'app\' from partially initialized module \'app\'的意思是，当Python编译一个文件时，它需要编译另一个\xe2\x80\x93模块来导入。但是，第二个文件还需要导入才能读取，这是原始的第一个文件。所以 python 不能在不编译另一个的情况下编译一个。

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最好的解决方案是简单地在 app.py 文件末尾导入 app.routes ，如下所示：

\n

from flask import Flask, render_template #imports at the top\n\n#the rest of your code\n\nfrom app import routes\n

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那应该可以解决问题。

\n

保持from app import app在routes.py 的顶部。请记住，应用程序目录中没有init .py 可能会导致导入困难。

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编辑：

\n

正如之前阿纳金所说，导入语句不必位于文件末尾。相反，它可以定位在app初始化后的任何点：

\n

应用程序.py：

\n

# create and configure the app, an instance of Flask\napp = Flask(__name__)\n    \n# account routes\nfrom user import routes\n

\n