我正在嘗試將 Flask webapp 轉換為在 PythonAnywhere 上運行，而不是在我當前托管并完美運行的 Raspberry Pi 上運行。
webapp 的核心功能之一是使用 Pandas 查詢外部托管的 MySQL 資料庫（不在 PythonAnywhere 上托管）。
以前我使用以下方法完成了此操作，沒有遇到任何麻煩：
import pandas as pd
URI=f"mysql://{user}@{host}:{port}/{schema}"
my_dataframe=pd.read_sql_query(sql="select * from users",con=URI)
使用 PythonAnywhere 上托管的 webapp 嘗試此操作會導致 502 后端錯誤，錯誤日志為：
File "./webapp.py", line 240, in ages
message_, success=scripts.ages.main()
File "./scripts/ages.py", line 22, in main
my_dataframe=pd.read_sql_query(sql="select * from users",con=URI)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/pandas/io/sql.py", line 383, in read_sql_query
chunksize=chunksize,
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/pandas/io/sql.py", line 1295, in read_query
result = self.execute(*args)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/pandas/io/sql.py", line 1162, in execute
*args, **kwargs
File "<string>", line 2, in execute
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/deprecations.py", line 401, in warned
return fn(*args, **kwargs)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3145, in execute
connection = self.connect(close_with_result=True)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3204, in connect
return self._connection_cls(self, close_with_result=close_with_result)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 96, in __init__
else engine.raw_connection()
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3283, in raw_connection
return self._wrap_pool_connect(self.pool.connect, _connection)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3254, in _wrap_pool_connect
e, dialect, self
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 2101, in _handle_dbapi_exception_noconnection
sqlalchemy_exception, with_traceback=exc_info[2], from_=e
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
raise exception
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 3250, in _wrap_pool_connect
return fn()
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 310, in connect
return _ConnectionFairy._checkout(self)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 868, in _checkout
fairy = _ConnectionRecord.checkout(pool)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 476, in checkout
rec = pool._do_get()
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/impl.py", line 146, in _do_get
self._dec_overflow()
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 72, in __exit__
with_traceback=exc_tb,
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
raise exception
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/impl.py", line 143, in _do_get
return self._create_connection()
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 256, in _create_connection
return _ConnectionRecord(self)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 371, in __init__
self.__connect()
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 666, in __connect
pool.logger.debug("Error on connect(): %s", e)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 72, in __exit__
with_traceback=exc_tb,
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
raise exception
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/pool/base.py", line 661, in __connect
self.dbapi_connection = connection = pool._invoke_creator(self)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/create.py", line 590, in connect
return dialect.connect(*cargs, **cparams)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 597, in connect
return self.dbapi.connect(*cargs, **cparams)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/MySQLdb/__init__.py", line 130, in Connect
return Connection(*args, **kwargs)
File "/home/mywebapp/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/MySQLdb/connections.py", line 185, in __init__
super().__init__(*args, **kwargs2)
sqlalchemy.exc.OperationalError: (MySQLdb._exceptions.OperationalError) (2003, "Can't connect to MySQL server on '34.105.08.12:8080' (111)")
(Background on this error at: https://sqlalche.me/e/14/e3q8)
（我已經改變了IP）
我查看了鏈接站點https://sqlalche.me/e/14/e3q8，但沒有看到任何有用的內容。
我還嘗試使用谷歌搜索如何在 PythonAnywhere 中使用 sqlalchemy。這主要導致有關連接到由 PythonAnywhere 托管的資料庫的問題，這對我沒有幫助。
我遇到了這個鏈接：
https://help.pythonanywhere.com/pages/UsingSQLAlchemywithMySQL/
我實際上不知道它是指使用 SQLAlchemy 連接到 PythonAnywhere 托管的 MySQL 資料庫還是外部資料庫，但我還是嘗試實作它。我懷疑它會有所不同，但 URI 位于 Pandas sql 查詢的單獨檔案中。
#credentials.py
from sqlalchemy import create_engine
URI_string=f"mysql://{user}@{host}:{port}/{schema}"
URI = create_engine(URI_string, pool_recycle=280)
import pandas as pd
import credentials
my_dataframe=pd.read_sql_query(sql="select * from users",con=credentials.URI)
使用此更改在 Pi 上進行測驗時，Web 應用程式仍然可以運行，但是在 PyAnywhere 上進行測驗時，結果沒有任何區別，并且收到了相同的錯誤日志輸出。
如果有人有任何想法，請告訴我！
uj5u.com熱心網友回復：
如果您使用的是免費帳戶，您將只能使用 http(s) 從 PythonAnywhere 連接到已批準的站點串列。因此，外部資料庫連接將無法通過免費帳戶作業。
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標籤：Python 烧瓶 sqlalchemy 蟒蛇无处不在