[英]Python, unable to import
I've asked a similar question before and without having found a solution I've simplified my code as much as possible to illustrate the problem. 我之前和之后都问了一个类似的问题我没有找到解决方案我尽可能地简化了我的代码来说明问题。
The code below runs fine, until I include from run import db
in models.py
. 下面的代码运行正常,直到我在
models.py
包含from run import db
。 Then I get ImportError: cannot import name 'Site'
(full error below) 然后我得到
ImportError: cannot import name 'Site'
(下面的完整错误)
However when I use from models import *
then everything runs fine again (but I don't want to do that). 但是当我使用
from models import *
然后一切都运行良好(但我不想这样做)。
Why does this happen? 为什么会这样?
run.py run.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = "sqlite:///database/db.db"
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy()
from models import Site
# from models import *
print (Site.hello())
models.py models.py
# Uncommenting the import line below produces the error
# from run import db
class Site():
def hello():
print ("hello world")
Error 错误
(venv) abc:projectx me$ python run.py
Traceback (most recent call last):
File "run.py", line 16, in <module>
from models import Site
File "/Users/me/projectx/models.py", line 1, in <module>
from run import db
File "/Users/me/projectx/run.py", line 16, in <module>
from models import Site
ImportError: cannot import name 'Site'
Directory structure 目录结构
projectx
__pycache__
database
venv
__init__.py
run.py
models.py
You are importing Site
from module "models" into module "run" and db
from module "run" into module "models" so you have a circular dependency problem. 您正在将模块“models”中的
Site
导入到模块“run”中,并将db
从模块“run”导入到模块“models”中,因此您会遇到循环依赖性问题。
You should keep your models simple so I would remove the dependency from module "run" inside "models" but if you still need it, then you should consider creating a single module that includes both because in this case, it would be sensible to make a single unit containing all dependant code. 你应该保持你的模型简单,所以我会从“模型”里面的模块“run”中删除依赖,但是如果你仍然需要它,那么你应该考虑创建一个包含两者的单个模块,因为在这种情况下,制作是明智的包含所有相关代码的单个单元。
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