Python - AttributeError：\'NoneType\' 对象没有属性 \'cursor\' python flask

Question

我正在尝试使用数据库中的数据在我的 webapp 中填充课程选择字段。 这是我的尝试。

这是表格 `

class StudentForm(FlaskForm):
    idnumber = StringField('ID Number', [validators.DataRequired(), validators.Length(min=9, max=9)])
    fname = StringField('First Name', [validators.DataRequired(), validators.Length(max=50)])
    mname = StringField('Middle Name', [validators.Length(max=50)])
    lname = StringField('Last Name', [validators.DataRequired(), validators.Length(max=50)])
    gender = SelectField('Gender', choices=gengen)
    yearlvl = SelectField('Year Level', choices= year_level)
    course = SelectField('Course', choices= models.Courses.populate())
    submit = SubmitField("Save")

`

    @classmethod
    def populate(cls):
        curs = mysql.connection.cursor()

        sql = curs.execute("SELECT COURSEID from courses")
        if sql > 0:
            result = curs.fetchall()
        return result

'

当我运行程序时出现此错误

`

  File "C:\laragon\SISwebapp\webapp\students\forms.py", line 15, in StudentForm
    course = SelectField('Course', choices= models.Courses.populate())
  File "C:\laragon\SISwebapp\webapp\models.py", line 87, in populate
    curs = mysql.connection.cursor()
AttributeError: 'NoneType' object has no attribute 'cursor'

` 我似乎无法弄清楚出了什么问题..

Answer 1

要创建游标，请使用连接对象的 cursor() 方法：

cnx = mysql.connector.connect(database='Hello_World')
cursor = cnx.cursor()