问题描述
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，用于为网站创建用户登录和注册页面。到目前为止，一切都可以在本教程中完成：在项目中的脚本中导入对象时，会出现此错误。
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",in <module>
from account import routes
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\account\routes.py",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",in locate_app
__import__(module_name)
File "C:\Users\dejar\OneDrive\Coding\Themes & Applications\002 Static Template\Install\app.py",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.
To switch between the interactive traceback and the plaintext one,you can click on the "Traceback" headline. From the text traceback you can also create a paste of it. For code execution mouse-over the frame you want to debug and click on the console icon on the right side.
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
dump(obj) dumps all that's kNown about the object
我没有发布我的实际应用程序，而是回过头来，仅在教程上复制了他的应用程序，该教程适用于他的Mac。但是会抛出与在PC上运行的实际应用相同的错误。我还尝试了以VS Code和Command-Line的环境作为管理员。在这里：
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
app.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")
models.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
routes.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
解决方法
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，它需要编译另一个文件-要导入的模块。但是，第二个文件也也需要读取导入，这是原始的第一个文件。因此python无法编译一个而不编译另一个。
最好的解决方案是简单地在app.py文件的 end 处导入app.routes，例如：
from flask import Flask,render_template #imports at the top
#the rest of your code
from app import routes
那应该可以解决问题。
将from app import app保留在route.py的顶部。请记住，应用目录中没有 init .py可能会导致导入困难。
编辑：
正如前analyanakin所说，import语句不必位于文件末尾。而是可以将其放置在app初始化之后的任意位置：
app.py：
# create and configure the app,an instance of Flask
app = Flask(__name__)
# account routes
from user import routes
在routes.py中，您从Flask导入了“ render_template”，而他没有。如果删除它会怎样？