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我在嘗試使用帶有Flask的MySQLdb時收到以下錯誤。 _mysql_exceptions.ProgrammingError: execute() first即使我在調用fetchall之前執行，MySQLdb仍會引發「執行（）第一個」錯誤
print輸出顯示「取回後」永遠不會打印，表示腳本在row = g.db.cursor().fetchall()處發生故障。爲什麼我得到這個錯誤，我該如何解決？
def connect_db():
return mysql.connection
@app.before_request
def before_request():
g.db = connect_db()
@app.teardown_request
def teardown_request(exception):
g.db.cursor().close()
@app.route('/login', methods=['GET', 'POST'])
def login():
if request.method == 'POST':
g.db.cursor().execute('SELECT * FROM users WHERE email = %s', [request.form['email']])
print('Before fetch')
row = g.db.cursor().fetchall()
print('After fetch')
if not row:
flash('No such user exists!')
return redirect(url_for('show_home'))
elif request.form['password'] == row[0][1]:
return redirect(url_for('show_dashboard'))
else:
flash('Wrong password/login error.')
return redirect(url_for('show_home'))
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/_compat.py", line 33, in reraise
raise value
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/_compat.py", line 33, in reraise
raise value
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/media/common/code/python/projects/up2date/up2date.py", line 47, in login
row = g.db.cursor().fetchall()
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/MySQLdb/cursors.py", line 406, in fetchall
self._check_executed()
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/MySQLdb/cursors.py", line 107, in _check_executed
self.errorhandler(self, ProgrammingError, "execute() first")
File "/media/common/code/python/projects/up2date/venv/lib/python3.4/site-packages/MySQLdb/connections.py", line 38, in defaulterrorhandler
Open an interactive python shell in this frameraise errorclass(errorvalue)